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Diseases

Genetic and Rare Diseases Information Center (GARD)

Search for Rare or Genetic Diseases


Diseases Beginning With O

The purpose of the Rare Diseases and Related Terms list is to distribute information; although the list is updated regularly, it should not be used as a reference or guarantee that a condition is rare. The prevalence of a rare disease is usually an estimate and may change over time. A rare (or orphan) disease is generally considered to have a prevalence of fewer than 200,000 affected individuals in the United States.

* This symbol indicates that a condition is not rare but is one for which a question has been answered by the GARD Information Center.
Is Rare Condition? Disease Name
* O Donnell Pappas syndrome
* OA1 - See Ocular albinism type 1
* OAFNS - See Oculoauriculofrontonasal syndrome
* OAK - See Optic atrophy 1
* OASD - See Albinism ocular late onset sensorineural deafness
* OAT deficiency - See Gyrate atrophy of choroid and retina
* OAVD - See Oculo-auriculo-vertebral spectrum
* OAVS with radial defect - See Microsomia hemifacial radial defects
*   Obesity
* Obesity due to pro-opiomelanocortin deficiency - See Proopiomelanocortin deficiency
* Obesity, early-onset, adrenal insufficiency, and red hair - See Proopiomelanocortin deficiency
* Obesity, mental retardation, body asymmetry, and muscle weakness - See Camera Marugo Cohen syndrome
* Obesity, muscular hypotonia, mental retardation, short stature, hypogonadotropic hypogonadism, and small hands and feet - See Prader-Willi syndrome
* Oblique facial clefts - See Oculomaxillofacial dysostosis
* Obliterative bronchiolitis - See Bronchiolitis obliterans
* OCA - See Oculocutaneous albinism
* OCA1 - See Oculocutaneous albinism type 1
* OCA1A - See Oculocutaneous albinism type 1
* OCA1B - See Oculocutaneous albinism type 1B
* OCA2 - See Oculocutaneous albinism type 2
* OCA3 - See Oculocutaneous albinism type 3
* OCC Syndrome - See Oculocerebrocutaneous syndrome
* Occipital atretic cephalocele, unusual facies and large feet - See Zechi Ceide syndrome
* Occipital horn syndrome
* Occlusive infantile arteriopathy - See Arterial calcification of infancy
* Occlusive peripheral vascular disease - See Buerger disease
* OCCS - See Oculocerebrocutaneous syndrome
*   Occult spina bifida - See Spina bifida occulta
* Occult spinal dysraphism
* Occult spinal dysraphism sequence - See Occult spinal dysraphism
* Ochoa syndrome
* Ochronosis
* Ochronosis, acquired - See Exogenous ochronosis
* Ochronosis, hereditary - See Alkaptonuria
* OCRL - See Lowe oculocerebrorenal syndrome
* OCRL1 - See Lowe oculocerebrorenal syndrome
* OCTD - See MASS syndrome
* Ocular albinism type 1
* Ocular albinism with sensorineural deafness - See Albinism ocular late onset sensorineural deafness
* Ocular cicatricial pemphigoid
* Ocular colobomas, ichthyosis, brain malformations and endocrine abnormalities
* Ocular MD - See Ocular Muscular Dystrophy
* Ocular melanoma
* Ocular motility disorders
* Ocular motility disorders - See Motor neuro-ophthalmic disorders
* Ocular Muscular Dystrophy
* Ocular neuromyotonia
* Ocular nonnephropathic cystinosis - See Cystinosis, ocular nonnephropathic
* Ocular toxoplasmosis
* Oculo cerebro acral syndrome
* Oculo cerebro osseous syndrome
* Oculo digital syndrome
* Oculo skeletal renal syndrome
* Oculoauriculofrontonasal dysplasia - See Oculoauriculofrontonasal syndrome
* Oculoauriculofrontonasal syndrome
* Oculo-Auriculo-Vertebral Dysplasia - See Oculo-auriculo-vertebral spectrum
* Oculo-auriculo-vertebral spectrum
* Oculoauriculovertebral spectrum with radial defect - See Microsomia hemifacial radial defects
* Oculo-cerebral dysplasia
* Oculocerebral hypopigmentation syndrome - See Oculocerebral syndrome with hypopigmentation
* Oculocerebral hypopigmentation syndrome type Preus
* Oculocerebral syndrome with hypopigmentation
* Oculocerebrocutaneous syndrome
* Oculo-cerebro-cutaneous syndrome - See Oculocerebrocutaneous syndrome
* Oculocerebrorenal syndrome - See Lowe oculocerebrorenal syndrome
* Oculocraniosomatic syndrome - See Kearns Sayre syndrome
* Oculocutaneous albinism
* Oculocutaneous albinism type 1
* Oculocutaneous albinism type 1A - See Oculocutaneous albinism type 1
* Oculocutaneous albinism type 1B
* Oculocutaneous albinism type 2
* Oculocutaneous albinism type 3
* Oculocutaneous albinism tyrosinase positive - See Oculocutaneous albinism type 2
* Oculocutaneous albinism, immunodeficiency, hematological disorders, and minor anomalies - See Kotzot-Richter syndrome
* Oculocutaneous albinism, minimal pigment type - See Albinism, minimal pigment type
* Oculocutaneous albinism, tyrosinase negative - See Oculocutaneous albinism type 1
* Oculocutaneous tyrosinemia - See Tyrosinemia type 2
* Oculodentodigital dysplasia
* Oculo-dento-digital dysplasia - See Oculodentodigital dysplasia
* Oculodentodigital dysplasia dominant
* Oculodentodigital syndrome - See Oculodentodigital dysplasia
* Oculo-dento-digital syndrome - See Oculodentodigital dysplasia
* Oculodentoosseous dysplasia recessive
* Oculodigitoesophagoduodenal syndrome - See Feingold syndrome
* Oculoectodermal syndrome
* Oculo-ectodermal syndrome - See Oculoectodermal syndrome
* Oculofaciocardiodental syndrome
* Oculogastrointestinal muscular dystrophy - See Familial visceral myopathy with external ophthalmoplegia
* Oculogastrointestinal muscular dystrophy - See Mitochondrial neurogastrointestinal encephalopathy syndrome
* Oculomaxillofacial dysostosis
* Oculomaxillofacial dysplasia with oblique facial clefts - See Oculomaxillofacial dysostosis
* Oculomelic amyoplasia - See Distal arthrogryposis type 5
* Oculomotor apraxia Cogan type
* Oculootofacial dysplasia
* Oculootoradial syndrome - See IVIC syndrome
* Oculopalatoskeletal syndrome - See Michels syndrome
* Oculopharyngeal muscular dystrophy
* Oculorenocerebellar syndrome
* Oculo-skeletal-abdominal syndrome - See Carnevale syndrome
* Oculosympathetic Palsy - See Horner's syndrome
* Oculotrichoanal syndrome - See Manitoba oculotrichoanal syndrome
* OD - See Osteochondritis dissecans
* ODCD - See Spondylometaphyseal dysplasia with dentinogenesis imperfecta
* ODD syndrome - See Oculodentodigital dysplasia
* ODDD - See Oculodentodigital dysplasia
* ODED syndrome - See Feingold syndrome
* ODOD recessive - See Oculodentoosseous dysplasia recessive
* O'Doherty syndrome - See Ermine phenotype
* Odonto onycho dysplasia with alopecia
* Odontochondrodysplasia - See Spondylometaphyseal dysplasia with dentinogenesis imperfecta
* Odontogenic myxoma
* Odontoma
* Odontoma dysphagia syndrome
* Odontomatosis (multiple odontomas) with dysphagia - See Odontoma dysphagia syndrome
* Odontomicronychial dysplasia
* Odonto-micronychial dysplasia - See Odontomicronychial dysplasia
* Odontoonychodermal dysplasia
* Odontotrichomelic hypohidrotic dysplasia - See Freire-Maia odontotrichomelic syndrome
* OEIS complex - See Omphalocele exstrophy imperforate anus
* OFCD syndrome - See Oculofaciocardiodental syndrome
* OFD syndrome 1 - See Orofaciodigital syndrome 1
* OFD syndrome 10 - See Orofaciodigital syndrome 10
* OFD syndrome 11 - See Orofaciodigital syndrome 11
* OFD syndrome 13 - See Orofaciodigital syndrome 13
* OFD syndrome 2 - See Orofaciodigital syndrome 2
* OFD syndrome 3 - See Orofaciodigital syndrome 3
* OFD syndrome 4 - See Orofaciodigital syndrome 4
* OFD syndrome 5 - See Orofaciodigital syndrome 5
* OFD syndrome 8 - See Orofaciodigital syndrome 8
* OFD syndrome 9 - See Orofaciodigital syndrome 9
* OFD syndrome with tibial defects - See Orofaciodigital syndrome 4
* OFD1 - See Orofaciodigital syndrome 1
* OFD10 - See Orofaciodigital syndrome 10
* OFD11 - See Orofaciodigital syndrome 11
* OFD12 - See Orofaciodigital syndrome 12
* OFD13 - See Orofaciodigital syndrome 13
* OFD2 - See Orofaciodigital syndrome 2
* OFD3 - See Orofaciodigital syndrome 3
* OFD4 - See Orofaciodigital syndrome 4
* OFD5 - See Orofaciodigital syndrome 5
* OFD6 - See Orofaciodigital syndrome 6
* OFD8 - See Orofaciodigital syndrome 8
* OFD9 - See Orofaciodigital syndrome 9
* OFDS 1 - See Orofaciodigital syndrome 1
* OFDS 10 - See Orofaciodigital syndrome 10
* OFDS 11 - See Orofaciodigital syndrome 11
* OFDS 12 - See Orofaciodigital syndrome 12
* OFDS 13 - See Orofaciodigital syndrome 13
* OFDS 2 - See Orofaciodigital syndrome 2
* OFDS 3 - See Orofaciodigital syndrome 3
* OFDS 4 - See Orofaciodigital syndrome 4
* OFDS 5 - See Orofaciodigital syndrome 5
* OFDS 8 - See Orofaciodigital syndrome 8
* OFDS 9 - See Orofaciodigital syndrome 9
* Ofuji disease - See Eosinophilic pustular folliculitis
* Ofuji's disease - See Eosinophilic pustular folliculitis
* OGD - See Osteoglophonic dysplasia
* Ogilvie syndrome
* Ogilvie's syndrome - See Ogilvie syndrome
* OGIMD - See Mitochondrial neurogastrointestinal encephalopathy syndrome
* Oguchi disease
* OHAHA syndrome - See Infantile onset spinocerebellar ataxia
* Ohara disease - See Tularemia
* Ohdo Blepharophimosis syndrome - See Blepharophimosis intellectual disability syndromes
* Ohdo syndrome - See Blepharophimosis intellectual disability syndromes
* OHS - See Occipital horn syndrome
* Ohtahara syndrome
* OI - See Osteogenesis imperfecta
* OI 9 - See Osteogenesis imperfecta type 9
* OI type 1 - See Osteogenesis imperfecta type 1
* OI type 1A - See Osteogenesis imperfecta type 1A
* OI type 2A - See Osteogenesis imperfecta type 2A
* OI type 2B - See Osteogenesis imperfecta type 2B
* OI type 3 - See Osteogenesis imperfecta type 3
* OI type 4 - See Osteogenesis imperfecta type 4
* OI type 5 - See Osteogenesis imperfecta type 5
* OI type 6 - See Osteogenesis imperfecta type 6
* OI type 7 - See Osteogenesis imperfecta type 7
* OI type IIA - See Osteogenesis imperfecta type 2A
* OI type IIB - See Osteogenesis imperfecta type 2B
* OI type III - See Osteogenesis imperfecta type 3
* OI type IV - See Osteogenesis imperfecta type 4
* Oi type IX - See Osteogenesis imperfecta type 9
* OI type V - See Osteogenesis imperfecta type 5
* OI type VI - See Osteogenesis imperfecta type 6
* OI type VII - See Osteogenesis imperfecta type 7
* OI type VIII - See Osteogenesis imperfecta type 8
* OI2A - See Osteogenesis imperfecta type 2A
* OI2B - See Osteogenesis imperfecta type 2B
* OI6 - See Osteogenesis imperfecta type 6
* OI8 - See Osteogenesis imperfecta type 8
* Okamoto syndrome
* Okihiro syndrome - See Duane-radial ray syndrome
* OKT deficiency - See Gyrate atrophy of choroid and retina
* Old Age Pemphigus - See Bullous pemphigoid
* Olfactory neuroblastoma - See Esthesioneuroblastoma
* Oligoarthritis, juvenile - See Pauciarticular onset juvenile idiopathic arthritis
* Oligoarticular onset juvenile idiopathic arthritis - See Pauciarticular onset juvenile idiopathic arthritis
* Oligoastrocytoma
* Oligodactyly tetramelic postaxial
* Oligodendroglioma
* Oligohydramnios sequence - See Potter syndrome
* Oligomeganephronia - See Oligomeganephronic renal hypoplasia
* Oligomeganephronic renal hypoplasia
* Oligophrenia phenylpyruvica - See Phenylketonuria
* Oliver McFarlane syndrome - See Trichomegaly with intellectual disability, dwarfism and pigmentary degeneration of retina
* Oliver syndrome
* Olivopontocerebellar atrophy
* Olivopontocerebellar atrophy 1 - See Spinocerebellar ataxia 1
* Olivopontocerebellar atrophy 2 - See Spinocerebellar ataxia 2
* Olivopontocerebellar atrophy 3 - See Spinocerebellar ataxia 7
* Olivopontocerebellar atrophy 4 - See Spinocerebellar ataxia 1
* Olivopontocerebellar atrophy deafness
* Olivopontocerebellar atrophy Holguin type - See Spinocerebellar ataxia 2
* Olivopontocerebellar hypoplasia fetal-onset - See Pontocerebellar hypoplasia type 5
* Ollier disease
* Olmsted syndrome
* Omani type of spondyloepiphyseal dysplasia - See Spondyloepiphyseal dysplasia Omani type
* Omenn syndrome
* OMM syndrome - See Pillay syndrome
* OMOD1 - See Omodysplasia 1
* OMOD2 - See Omodysplasia 2
* Omodysplasia 1
* Omodysplasia 2
* Omodysplasia autosomal recessive - See Omodysplasia 1
* Omodysplasia generalized form - See Omodysplasia 1
* Omodysplasia, autosomal dominant - See Omodysplasia 2
* Omphalocele cleft palate syndrome lethal
* Omphalocele exstrophy imperforate anus
* Omphalocele with hypoplasia of pharynx and larynx, learning disability, dysmorphic facies, and scoliosis - See Shprintzen omphalocele syndrome
* Omphalocele, diaphragmatic hernia, and radial ray defects - See Gershoni-Baruch syndrome
* Omphalocele, exstrophy of the cloaca, imperforate anus, and spinal defects - See Omphalocele exstrophy imperforate anus
* Omphalocele, laryngeal and pharyngeal hypoplasia, learning disabilities, dysmorphic facies and spinal anomalies - See Shprintzen omphalocele syndrome
* Omphalomesenteric cyst
* OMS - See Dancing eyes-dancing feet syndrome
* Omsk hemorrhagic fever
* Onat syndrome - See Subaortic stenosis short stature syndrome
* Onchocerciasis
* Oncocytic cardiomyopathy - See Infantile histiocytoid cardiomyopathy
* Oncocytoma kidney - See Renal oncocytoma
* Oncocytoma renal - See Renal oncocytoma
* Oncogenic osteomalacia
* Ondine curse (formerly) - See Congenital central hypoventilation syndrome
* Ondine's curse (formerly) - See Congenital central hypoventilation syndrome
* Onion whorl disease - See Localized hypertrophic neuropathy
* Onset of senility in the early teens, atrophic skin, hypogonadism, retinal and vascular sclerosis - See Ruvalcaba Churesigaew Myhre syndrome
* Onychocytic matricoma
* Onychodystrophy totalis, isolated - See Twenty-nail dystrophy
* Onychoosteodysplasia - See Nail patella syndrome
* Onychotrichodysplasia and neutropenia
* OO - See Oncogenic osteomalacia
* OOCH - See Osteoporosis oculocutaneous hypopigmentation syndrome
* OOCH syndrome - See Osteoporosis oculocutaneous hypopigmentation syndrome
* OOFD - See Oculootofacial dysplasia
* OOM - See Oncogenic osteomalacia
* OORS - See IVIC syndrome
* OPA1 - See Optic atrophy 1
* OPA2 - See Optic atrophy 2
* OPA3 - See Optic atrophy and cataract, autosomal dominant
* OPA6 - See Optic atrophy 6
* Opalescent dentin - See Dentinogenesis imperfecta 1
* Opalescent teeth without osteogenesis imperfecta - See Dentinogenesis imperfecta 1
* OPCA - See Olivopontocerebellar atrophy
* OPCA with macular degeneration and external ophthalmoplegia - See Spinocerebellar ataxia 7
* OPCA with retinal degeneration - See Spinocerebellar ataxia 7
* OPCA1 - See Spinocerebellar ataxia 1
* OPCA3 - See Spinocerebellar ataxia 7
* OPCA4 - See Spinocerebellar ataxia 1
* OPD 2 syndrome - See Oto-palato-digital syndrome type 2
* OPD syndrome - See Oto-palato-digital syndrome type 1
* OPD syndrome 1 - See Oto-palato-digital syndrome type 1
* OPD1 - See Oto-palato-digital syndrome type 1
* Open spine - See Spina bifida
* Ophthalmoacromelic syndrome - See Anophthalmos with limb anomalies
* Ophthalmo-mandibulo-melic dysplasia - See Pillay syndrome
* Ophthalmoplegia plus syndrome - See Kearns Sayre syndrome
* Ophthalmoplegia, hypotonia, ataxia, hypacusis, and athetosis - See Infantile onset spinocerebellar ataxia
* Ophthalmoplegia, pigmentary degeneration of retina, and cardiomyopathy - See Kearns Sayre syndrome
* Ophthalmoplegia, progressive external, with ragged red fibers - See Kearns Sayre syndrome
* Ophthalmoplegic MD - See Ophthalmoplegic Muscular dystrophy
* Ophthalmoplegic Muscular dystrophy
* Opisthorchiasis
* Opitz BBBG syndrome - See Opitz G/BBB syndrome
* Opitz G/BBB syndrome
* Opitz Mollica Sorge syndrome - See Acrofacial dysostosis Catania type
* Opitz trigonocephaly syndrome - See C syndrome
* Opitz trigonocephaly-like syndrome - See C-like syndrome
* Opitz-Frias syndrome - See Opitz G/BBB syndrome
* Opitz-G syndrome, type 2 - See Opitz G/BBB syndrome
* Opitz-Kaveggia syndrome - See FG syndrome
* OPLL - See Ossification of the posterior longitudinal ligament of the spine
* OPMD - See Oculopharyngeal muscular dystrophy
* Oppenheim disease - See Amyotonia congenita
* Oppenheim's disease - See Amyotonia congenita
* Oppenheim's dystonia - See Dystonia 1
* OPPG - See Osteoporosis-pseudoglioma syndrome
* OPS - See Osteoporosis-pseudoglioma syndrome
* Opsismodysplasia
* Opsoclonus myoclonus syndrome - See Dancing eyes-dancing feet syndrome
* OPTA1 - See Osteopetrosis autosomal dominant type 1
* OPTA2 - See Osteopetrosis autosomal dominant type 2
* OPTB1 - See Osteopetrosis autosomal recessive 1
* OPTB2 - See Osteopetrosis autosomal recessive 2
* OPTB3 - See Osteopetrosis autosomal recessive 3
* OPTB4 - See Osteopetrosis autosomal recessive 4
* OPTB5 - See Osteopetrosis autosomal recessive 5
* OPTB6 - See Osteopetrosis autosomal recessive 6
* OPTB7 - See Osteopetrosis autosomal recessive 7
* Opthalmic icthyosis
* Opthalmomandibulomelic dysplasia
* Opthalmoplegia mental retardation lingua scrotalis
* Opthalmoplegia myalgia tubular aggregates
* Opthalmoplegia progressive external scoliosis
* Optic atrophy 1
* Optic atrophy 1 and deafness
* Optic atrophy 2
* Optic atrophy 3 - See 3-methylglutaconic aciduria type III
* Optic atrophy 3 - See Optic atrophy and cataract, autosomal dominant
* Optic atrophy 5
* Optic atrophy 6
* Optic atrophy and cataract, autosomal dominant
* Optic atrophy in early childhood, associated with ataxia, spasticity, mental retardation, and posterior column sensory loss - See Behr syndrome
* Optic atrophy infantile with chorea and spastic paraplegia - See 3-methylglutaconic aciduria type III
* Optic atrophy opthalmoplegia ptosis deafness myopia
* Optic atrophy plus syndrome - See 3-methylglutaconic aciduria type III
* Optic atrophy polyneuropathy deafness
* Optic atrophy, cataract, and neurologic disorder - See Optic atrophy and cataract, autosomal dominant
* Optic atrophy, congenital or early infantile, autosomal recessive - See Optic atrophy 6
* Optic atrophy, hearing loss, and peripheral neuropathy, autosomal recessive - See Optic atrophy polyneuropathy deafness
* Optic atrophy, infantile hereditary, Behr complicated form of - See Behr syndrome
* Optic atrophy, juvenile - See Optic atrophy 1
* Optic atrophy, Kjer type - See Optic atrophy 1
* Optic atrophy, Leber type - See Leber hereditary optic neuropathy
* Optic atrophy, neural deafness, and distal neurogenic amyotrophy - See Optic atrophy polyneuropathy deafness
* Optic atrophy, non-Leber type, with early onset - See Optic atrophy 2
* Optic atrophy, polyneuropathy, and deafness - See X-linked Charcot-Marie-Tooth disease type 5
* Optic atrophy, sensorineural hearing loss and polyneuropathy - See X-linked Charcot-Marie-Tooth disease type 5
* Optic atrophy, X-linked - See Optic atrophy 2
* Optic coloboma, vesicoureteral reflux, and renal anomalies - See Renal coloboma syndrome
* Optic nerve coloboma - See Coloboma of optic nerve
* Optic nerve coloboma with renal disease - See Renal coloboma syndrome
* Optic nerve head pits, bilateral congenital - See Coloboma of optic nerve
* Optic nerve hypoplasia, familial bilateral
* Optic neuritis
* Optic neuropathy, anterior ischemic
* Optic pathway glioma
* Opticoacoustic nerve atrophy dementia
* Opticoacustic nerve atrophy with dementia - See Jensen syndrome
* Oral and digital anomalies with ichthyosis - See Ichthyosis tapered fingers midline groove up
* Oral cancer
* Oral facial digital syndrome 1 - See Orofaciodigital syndrome 1
* Oral facial digital syndrome 10 - See Orofaciodigital syndrome 10
* Oral facial digital syndrome 11 - See Orofaciodigital syndrome 11
* Oral facial digital syndrome 12 - See Orofaciodigital syndrome 12
* Oral facial digital syndrome 13 - See Orofaciodigital syndrome 13
* Oral facial digital syndrome 2 - See Orofaciodigital syndrome 2
* Oral facial digital syndrome 3 - See Orofaciodigital syndrome 3
* Oral facial digital syndrome 4 - See Orofaciodigital syndrome 4
* Oral facial digital syndrome 5 - See Orofaciodigital syndrome 5
* Oral facial digital syndrome 6 - See Orofaciodigital syndrome 6
* Oral facial digital syndrome 8 - See Orofaciodigital syndrome 8
* Oral facial digital syndrome 9 - See Orofaciodigital syndrome 9
* Oral facial digital syndrome type 1 - See Orofaciodigital syndrome 1
* Oral facial digital syndrome type 10 - See Orofaciodigital syndrome 10
* Oral facial digital syndrome type 11 - See Orofaciodigital syndrome 11
* Oral facial digital syndrome type 12 - See Orofaciodigital syndrome 12
* Oral facial digital syndrome type 13 - See Orofaciodigital syndrome 13
* Oral facial digital syndrome type 2 - See Orofaciodigital syndrome 2
* Oral facial digital syndrome type 3 - See Orofaciodigital syndrome 3
* Oral facial digital syndrome type 4 - See Orofaciodigital syndrome 4
* Oral facial digital syndrome type 5 - See Orofaciodigital syndrome 5
* Oral facial digital syndrome type 6 - See Orofaciodigital syndrome 6
* Oral facial digital syndrome type 8 - See Orofaciodigital syndrome 8
* Oral facial digital syndrome type 9 - See Orofaciodigital syndrome 9
* Oral facial digital syndromes - See Orofaciodigital syndromes
* Oral facial dystonia - See Meige syndrome
* Oral gangrene - See Noma
* Oral leukoplakia
* Oral lichen planus
* Oral lichenoid lesions - See Oral lichen planus
* Oral pharyngeal disorders
* Oral squamous cell carcinoma
* Oral submucous fibrosis
* Oral-facial-digital syndrome 1 - See Orofaciodigital syndrome 1
* Oral-facial-digital syndrome 10 - See Orofaciodigital syndrome 10
* Oral-facial-digital syndrome 12 - See Orofaciodigital syndrome 12
* Oral-facial-digital syndrome 12 - See Orofaciodigital syndrome 12
* Oral-facial-digital syndrome 13 - See Orofaciodigital syndrome 13
* Oral-facial-digital syndrome 5 - See Orofaciodigital syndrome 5
* Oral-facial-digital syndrome type 1 - See Orofaciodigital syndrome 1
* Oral-facial-digital syndrome type 11 - See Orofaciodigital syndrome 11
* Oral-facial-digital syndrome type 13 - See Orofaciodigital syndrome 13
* Oral-facial-digital syndrome type 2 - See Orofaciodigital syndrome 2
* Oral-facial-digital syndrome type 3 - See Orofaciodigital syndrome 3
* Oral-facial-digital syndrome type 4 - See Orofaciodigital syndrome 4
* Oral-facial-digital syndrome type 6 - See Orofaciodigital syndrome 6
* Oral-facial-digital syndrome type 8 - See Orofaciodigital syndrome 8
* Oral-facial-digital syndrome type 9 - See Orofaciodigital syndrome 9
* Oral-facial-digital syndrome with fibular aplasia - See Orofaciodigital syndrome 10
* Oral-facial-digital syndrome with hypoplastic epiglottis - See Orofaciodigital syndrome 8
* Oral-facial-digital syndrome with retinal abnormalities - See Orofaciodigital syndrome 9
* Oral-facial-digital syndrome with skeletal anomalies - See Orofaciodigital syndrome 11
* Oral-facial-digital syndrome XIII - See Orofaciodigital syndrome 13
* Oral-facial-digital syndromes - See Orofaciodigital syndromes
* Orbital cyst with cerebral and focal dermal malformations - See Oculocerebrocutaneous syndrome
* Orbital lymphangioma
* Orbital lymphoma
* Orbital melanoma
* Orbital varix
* Orbital venous varix - See Orbital varix
* ORC syndrome - See Oculorenocerebellar syndrome
* Oregon type tyrosinemia - See Tyrosinemia type 2
* Organic acidemia
* Organic mood syndrome
* Organoid nevus phakomatosis - See Linear nevus sebaceous syndrome
* Organoid nevus with sebaceous differentiation, a speckled-lentiginous nevus, and other associated anomalies - See Phacomatosis pigmentokeratotica
* Ormond's disease - See Retroperitoneal fibrosis
* Ornithine aminotransferase deficiency - See Gyrate atrophy of choroid and retina
* Ornithine carbamoyltransferase deficiency - See Ornithine transcarbamylase deficiency
* Ornithine ketoacid aminotransferase deficiency - See Gyrate atrophy of choroid and retina
* Ornithine transcarbamylase deficiency
* Ornithine translocase deficiency - See Ornithine translocase deficiency syndrome
* Ornithine translocase deficiency syndrome
* Ornithinemia
* Ornithosis - See Psittacosis
* Oroacral syndrome - See Oro-mandibular-limb hypogenesis syndrome
* Orocraniodigital syndrome - See Juberg-Hayward syndrome
* Oro-facial gangrene - See Noma
* Oro-facial noma - See Noma
* Orofaciodigital syndrome - See Orofaciodigital syndromes
* Orofaciodigital syndrome 1
* Orofaciodigital syndrome 10
* Orofaciodigital syndrome 11
* Orofaciodigital syndrome 12
* Orofaciodigital syndrome 13
* Orofaciodigital syndrome 2
* Orofaciodigital syndrome 3
* Orofaciodigital syndrome 4
* Orofaciodigital syndrome 5
* Orofaciodigital syndrome 6
* Orofaciodigital syndrome 8
* Orofaciodigital syndrome 9
* Orofaciodigital syndrome I - See Orofaciodigital syndrome 1
* Orofaciodigital syndrome II - See Orofaciodigital syndrome 2
* Orofaciodigital syndrome III - See Orofaciodigital syndrome 3
* Orofaciodigital syndrome IV - See Orofaciodigital syndrome 4
* Orofaciodigital syndrome IX - See Orofaciodigital syndrome 9
* Orofaciodigital syndrome type 8 - See Orofaciodigital syndrome 8
* Orofaciodigital syndrome type Figuera - See Orofaciodigital syndrome 10
* Orofaciodigital syndrome V - See Orofaciodigital syndrome 5
* Orofaciodigital syndrome VI - See Orofaciodigital syndrome 6
* Orofaciodigital syndrome VIII - See Orofaciodigital syndrome 8
* Orofaciodigital syndrome with fibular aplasia - See Orofaciodigital syndrome 10
* Orofaciodigital syndrome with retinal abnormalities - See Orofaciodigital syndrome 9
* Orofaciodigital syndrome with tibial dysplasia - See Orofaciodigital syndrome 4
* Orofaciodigital syndrome X - See Orofaciodigital syndrome 10
* Orofaciodigital syndrome XI - See Orofaciodigital syndrome 11
* Orofaciodigital syndrome XII - See Orofaciodigital syndrome 12
* Orofaciodigital syndrome XIII - See Orofaciodigital syndrome 13
* Orofaciodigital syndromes
* Oro-mandibular-limb hypogenesis syndrome
* Oropharyngeal cancer, adult
* Oropharyngeal cancer, childhood
* Oropharyngeal infection leading to secondary septic thrombophlebitis of the internal jugular vein - See Lemierre syndrome
* Orotate phosphoribosyltransferase and omp decarboxylase deficiency - See Orotic aciduria type 1
* Orotic aciduria II (formerly) - See Orotic aciduria type 1
* Orotic aciduria type 1
* Oroticaciduria 1 - See Orotic aciduria type 1
* Orotidylic pyrophosphorylase and orotidylic decarboxylase deficiency - See Orotic aciduria type 1
* Orstavik Lindemann Solberg syndrome
* Orthostatic hypotension (a symptom) - See Pure autonomic failure
* Orthostatic hypotension, bladder and bowel incontinence, anhidrosis, iris atrophy, amyotrophy, ataxia, rigidity and tremor - See Multiple system atrophy (MSA) with orthostatic hypotension
* Orthostatic tremor, primary - See Primary orthostatic tremor
* ORW disease - See Hereditary hemorrhagic telangiectasia
* ORW1 - See Hereditary hemorrhagic telangiectasia
* ORW2 - See Hereditary hemorrhagic telangiectasia type 2
* ORW3 - See Hereditary hemorrhagic telangiectasia type 3
* OSA syndrome - See Carnevale syndrome
* OSCS - See Osteopathia striata cranial sclerosis
* Osebold-Remondini syndrome - See Brachydactyly type A6
* Oslam syndrome
* Osler Weber Rendu syndrome - See Hereditary hemorrhagic telangiectasia
* Osler Weber Rendu syndrome type 1 - See Hereditary hemorrhagic telangiectasia
* Osler Weber Rendu syndrome type 2 - See Hereditary hemorrhagic telangiectasia type 2
* Osler Weber Rendu syndrome type 3 - See Hereditary hemorrhagic telangiectasia type 3
* Osler-Rendu-Weber disease - See Hereditary hemorrhagic telangiectasia
* OSMED - See OSMED Syndrome
* OSMED Syndrome
* Ossicular Malformations, familial
* Ossification of the posterior longitudinal ligament of the spine
* Ossified ear cartilages with mental deficiency, muscle wasting, and bony changes - See Primrose syndrome
* Ossifying fibroma - See Osteofibrous dysplasia
*   Osteitis deformans - See Paget disease of bone
* Osteoarthropathy of fingers familial
* Osteoarthropathy, premature degenerative, of hip - See Beukes familial hip dysplasia
* Osteochondritis deformans - See Legg-Calve-Perthes disease
* Osteochondritis dissecans
* Osteochondrodysplasia with rhizomelia, platyspondyly, callosal agenesis, thrombocytopenia, hydrocephalus, and hypertension - See Faye-Petersen-Ward-Carey syndrome
* Osteochondroma
* Osteochondrosis deformans tibiae - See Blount disease
* Osteochondrosis deformans tibiae, familial infantile type - See Blount disease
* Osteochondrosis of the metatarsal head, usually the second - See Freiberg's disease
* Osteocraniosplenic syndrome - See Gracile bone dysplasia
* Osteocraniostenosis - See Gracile bone dysplasia
* Osteodysgenesis, multisynostotic with fractures - See Antley Bixler syndrome
* Osteodysplasia familial Anderson type
* Osteodysplastic primordial dwarfism type 2 - See Microcephalic osteodysplastic primordial dwarfism type 2
* Osteodysplastic primordial dwarfism type I - See Microcephalic osteodysplastic primordial dwarfism type 1
* Osteodysplasty of Melnick and Needles - See Melnick-Needles syndrome
* Osteodysplasty precocious of Danks Mayne and Kozlowski
* Osteoectasia familial
* Osteofibrous dysplasia
* Osteogenesis imperfecta
* Osteogenesis imperfecta congenita - See Osteogenesis imperfecta type 2A
* Osteogenesis imperfecta congenita microcephaly and cataracts
* Osteogenesis imperfecta congenita perinatal lethal form - See Osteogenesis imperfecta type 2A
* Osteogenesis imperfecta Levin type
* Osteogenesis imperfecta ocular form - See Osteoporosis-pseudoglioma syndrome
* Osteogenesis imperfecta retinopathy seizures intellectual deficit - See Al Gazali Sabrinathan Nair syndrome
* Osteogenesis imperfecta sillence type II/III without abnormality of type I collagen - See Osteogenesis imperfecta type 9
* Osteogenesis imperfecta tarda - See Osteogenesis imperfecta type 1
* Osteogenesis imperfecta type 1
* Osteogenesis imperfecta type 1 with dentinogenesis imperfecta - See Osteogenesis imperfecta type 1A
* Osteogenesis imperfecta type 1A
* Osteogenesis imperfecta type 2A
* Osteogenesis imperfecta type 2B
* Osteogenesis imperfecta type 3
* Osteogenesis imperfecta type 4
* Osteogenesis imperfecta type 5
* Osteogenesis imperfecta type 6
* Osteogenesis imperfecta type 7
* Osteogenesis imperfecta type 8
* Osteogenesis imperfecta type 9
* Osteogenesis imperfecta with blue sclerae - See Osteogenesis imperfecta type 1
* Osteogenesis imperfecta with congenital joint contractures - See Bruck syndrome 1
* Osteogenesis imperfecta with normal sclerae - See Osteogenesis imperfecta type 4
* Osteogenesis imperfecta with opalescent teeth - See Osteogenesis imperfecta type 1A
* Osteogenesis imperfecta with unusual skeletal lesions - See Osteogenesis imperfecta Levin type
* Osteogenesis imperfecta, perinatal lethal autosomal recessive - See Osteogenesis imperfecta type 2B
* Osteogenesis imperfecta, progressively deforming with normal sclerae - See Osteogenesis imperfecta type 3
* Osteogenic sarcoma - See Osteosarcoma
* Osteoglophonic dwarfism - See Osteoglophonic dysplasia
* Osteoglophonic dysplasia
* Osteolysis massive - See Gorham's disease
* Osteolysis syndrome recessive
* Osteolysis, distal, with short stature, mental retardation, and characteristic facial appearance - See Osteolysis syndrome recessive
* Osteolysis, familial expansile - See Polyostotic osteolytic dysplasia, hereditary expansile
* Osteolysis, hereditary multicentric - See Torg Winchester syndrome
* Osteoma cutis - See Progressive osseous heteroplasia
* Osteomalacia
* Osteomesopyknosis
* Osteomyelitis
* Osteo-Onychodysplasia - See Nail patella syndrome
* Osteopathia condensans disseminata - See Buschke Ollendorff syndrome
* Osteopathia condensans disseminata - See Osteopoikilosis
* Osteopathia striata associated with familial dermopathy and white forelock - See Osteopathia striata with pigmentary dermopathy including white forelock
* Osteopathia striata cranial sclerosis
* Osteopathia striata with pigmentary dermopathy including white forelock
* Osteopenia and sparse hair
* Osteopenia mental retardation sparse hair - See Osteopenia and sparse hair
* Osteopetroses - See Osteopetrosis
* Osteopetrosis
* Osteopetrosis and infantile neuroaxonal dystrophy
* Osteopetrosis autosomal dominant type 1
* Osteopetrosis autosomal dominant type 2
* Osteopetrosis autosomal recessive 1
* Osteopetrosis autosomal recessive 2
* Osteopetrosis autosomal recessive 3
* Osteopetrosis autosomal recessive 4
* Osteopetrosis autosomal recessive 5
* Osteopetrosis autosomal recessive 6
* Osteopetrosis autosomal recessive 7
* Osteopetrosis autosomal recessive intermediate form - See Osteopetrosis autosomal recessive 6
* Osteopetrosis infantile malignant 1 - See Osteopetrosis autosomal recessive 1
* Osteopetrosis infantile malignant 2 - See Osteopetrosis autosomal recessive 4
* Osteopetrosis infantile malignant 3 - See Osteopetrosis autosomal recessive 5
* Osteopetrosis osteoclast-poor - See Osteopetrosis autosomal recessive 2
* Osteopetrosis osteoclast-poor with hypogammaglobulinemia - See Osteopetrosis autosomal recessive 7
* Osteopetrosis with renal tubular acidosis - See Osteopetrosis autosomal recessive 3
* Osteopoikilosis
* Osteopoikilosis and dacryocystitis
* Osteoporosis oculocutaneous hypopigmentation syndrome
* Osteoporosis pseudoglioma syndrome - See Osteoporosis-pseudoglioma syndrome
* Osteoporosis, juvenile - See Juvenile osteoporosis
* Osteoporosis-pseudoglioma syndrome
* Osteosarcoma
* Osteosarcoma, limb anomalies (clinodactyly, absence of digital ray in foot, bilateral radioulnar synostosis) and macrocytosis without anemia - See Oslam syndrome
* Osteosarcoma, limb anomalies, and erythroid macrocytosis with megaloblastic marrow - See Oslam syndrome
* Osteosclerosis abnormalities of nervous system and meninges
* Osteosclerosis fragilis - See Osteopetrosis
* Osteosclerosis of the skull and enlarged mandible - See Van Buchem disease type 2
* Osteosclerosis with ichthyosis and POF - See Osteosclerosis with ichthyosis and premature ovarian failure
* Osteosclerosis with ichthyosis and premature ovarian failure
* Osteosclerosis, autosomal dominant - See Hyperostosis corticalis generalisata, benign form of Worth with torus palatinus
* Osteosclerosis, autosomal dominant, Worth type - See Hyperostosis corticalis generalisata, benign form of Worth with torus palatinus
* Ostertag type amyloidosis - See Amyloidosis familial visceral
* Ostium primum ASD - See Atrial septal defect ostium primum
* Ostium secundum ASD - See Atrial septal defect ostium secundum
* OT - See Primary orthostatic tremor
* OTC deficiency - See Ornithine transcarbamylase deficiency
* OTCD - See Ornithine transcarbamylase deficiency
* Otodental dysplasia
* Otofaciocervical syndrome
* Otoonychoperoneal syndrome
* Oto-onycho-peroneal syndrome - See Otoonychoperoneal syndrome
* Oto-Palatal-digital syndrome
* Otopalatodigital syndrome type 1 - See Oto-palato-digital syndrome type 1
* Oto-palato-digital syndrome type 1
* Otopalatodigital syndrome type 2 - See Oto-palato-digital syndrome type 2
* Oto-palato-digital syndrome type 2
* Otosclerosis, familial
* Otospondylomegaepiphyseal dysplasia - See OSMED Syndrome
* Oto-Spondylo-Mega-Epiphyseal Dysplasia - See OSMED Syndrome
* Otto syndrome - See Arthrogryposis multiplex congenita
* Oudtshoorn skin - See Keratolytic winter erythema
* Ouvrier Billson syndrome
* Ovarian Brenner tumor - See Brenner tumor of ovary
* Ovarian cancer
* Ovarian cancer, childhood
* Ovarian cancer, epithelial - See Ovarian epithelial cancer
* Ovarian carcinoma - See Ovarian cancer
* Ovarian carcinoma, childhood - See Ovarian cancer, childhood
* Ovarian carcinosarcoma
* Ovarian dysgenesis with sensorineural deafness - See Gonadal dysgenesis, XX type
* Ovarian epithelial cancer
* Ovarian epithelial carcinoma - See Ovarian epithelial cancer
* Ovarian germ cell tumor
* Ovarian gynandroblastoma - See Gynandroblastoma
* Ovarian insufficiency due to FSH resistance
* Ovarian insufficiency, familial
* Ovarian low malignant potential tumor
* Ovarian remnant syndrome
* Ovarian small cell carcinoma
* Overgrowth - craniosynostosis - arthrogryposis - See Richieri-Costa Guion-Almeida Cohen syndrome
* Overgrowth radial ray defect arthrogryposis
* Overgrowth syndrome with accelerated skeletal maturation, unusual facies, and camptodactyly - See Weaver syndrome
* Overhydrated hereditary stomatocytosis - See Stomatocytosis I
* Overlap connective tissue disease - See MASS syndrome
* Ovoid neutrophil nuclei, developmental delay, epilepsy and skeletal abnormalities - See Pelger-Huet anomaly
* Ovoid pupils - See Egg shaped pupils
* Oxalosis 1 - See Primary hyperoxaluria type 1
* Oxalosis 2 - See Primary hyperoxaluria type 2
* Oxoglutaricaciduria - See Alpha-ketoglutarate dehydrogenase deficiency
* Oxoprolinase deficiency - See Glutathione synthetase deficiency
* Oxoprolinuria due to 5-oxoprolinase deficiency - See 5-oxoprolinase deficiency
* Oxyuriasis - See Enterobiasis