Pycnodysostosis

Title

Other Names:

Pyknodysostosis; PKND; PYCD

Categories:

Congenital and Genetic Diseases; Metabolic disorders; Musculoskeletal Diseases

Summary Summary

Pycnodysostosis impacts bone growth and is present from birth. Symptoms include a large head and high forehead, undeveloped facial bones, and short fingers and toes. People with pycnodysostosis may have short stature, dental abnormalities, brittle bones, and delayed closure of the skull bones. Bones may become more brittle with age. Other complications like trouble breathing during sleep (sleep apnea) and bone infections may occur. Pycnodysostosis is caused by a CTSK gene that is not working correctly and inherited in an autosomal recessive pattern. The diagnosis of pycnodysostosis is based on clinical examination and X-ray findings, and is confirmed by genetic testing. Treatment is based on managing the symptoms.^[1]^[2]^[3]

Last updated: 6/5/2020

Symptoms Symptoms

The following list includes the most common signs and symptoms in people with pycnodysostosis. These features may be different from person to person. Some people may have more symptoms than others and symptoms can range from mild to severe. This list does not include every symptom or feature that has been described in this condition.

Signs and symptoms may include:^[2]^[3]

Short bones
Loss of bone tissue from the hands (acro-osteolysis)
Delayed closure of the skull bones
Underdeveloped facial bones
Thickening of the face and skull bones
Dental anomalies

Many of the signs of pycnodysostosis are present at birth. People with pycnodysostosis are usually shorter than average and have normal intellectual development. Bone infections (osteomyelitis) and trouble breathing during sleep (sleep apnea) may also occur. The bones often get more brittle with time.^[2]

Last updated: 6/8/2020

This table lists symptoms that people with this disease may have. For most diseases, symptoms will vary from person to person. People with the same disease may not have all the symptoms listed. This information comes from a database called the Human Phenotype Ontology (HPO) . The HPO collects information on symptoms that have been described in medical resources. The HPO is updated regularly. Use the HPO ID to access more in-depth information about a symptom.

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Medical Terms	Other Names	Learn More: HPO ID
80%-99% of people have these symptoms
Abnormal clavicle morphology	Abnormal collarbone	0000889
Abnormal fingernail morphology	Abnormal fingernails Abnormality of the fingernails [ more ]	0001231
Abnormal pelvis bone ossification		0009106
Abnormal vertebral morphology		0003468
Abnormality of epiphysis morphology	Abnormal shape of end part of bone	0005930
Brachycephaly	Short and broad skull	0000248
Brachydactyly	Short fingers or toes	0001156
Delayed eruption of teeth	Delayed eruption Delayed teeth eruption Delayed tooth eruption Eruption, delayed Late eruption of teeth Late tooth eruption [ more ]	0000684
Frontal bossing		0002007
High forehead		0000348
Malar flattening	Zygomatic flattening	0000272
Midface retrusion	Decreased size of midface Midface deficiency Underdevelopment of midface [ more ]	0011800
Narrow palate	Narrow roof of mouth	0000189
Osteolysis	Breakdown of bone	0002797
Persistent open anterior fontanelle		0004474
Recurrent fractures	Increased fracture rate Increased fractures Multiple fractures Multiple spontaneous fractures Varying degree of multiple fractures [ more ]	0002757
Short distal phalanx of finger	Short outermost finger bone	0009882
Short stature	Decreased body height Small stature [ more ]	0004322
Short toe	Short toes Stubby toes [ more ]	0001831
Skeletal dysplasia		0002652
30%-79% of people have these symptoms
Abnormality of dental morphology	Abnormality of dental shape Abnormally shaped teeth Deformity of teeth Dental deformity Dental malformations Malformed teeth Misshapen teeth Misshapened teeth [ more ]	0006482
Blue sclerae	Whites of eyes are a bluish-gray color	0000592
Bone pain		0002653
Proptosis	Bulging eye Eyeballs bulging out Prominent eyes Prominent globes Protruding eyes [ more ]	0000520
Ridged nail	Grooved nails Nail ridging [ more ]	0001807
Wormian bones	Extra bones within cranial sutures	0002645
5%-29% of people have these symptoms
Abnormal pattern of respiration	Abnormal respiratory patterns Unusual breathing patterns [ more ]	0002793
Abnormality of the skin		0000951
Anemia	Low number of red blood cells or hemoglobin	0001903
Cognitive impairment	Abnormality of cognition Cognitive abnormality Cognitive defects Cognitive deficits Intellectual impairment Mental impairment [ more ]	0100543
Hepatomegaly	Enlarged liver	0002240
Hydrocephalus	Too much cerebrospinal fluid in the brain	0000238
Hyperlordosis	Prominent swayback	0003307
Kyphosis	Hunched back Round back [ more ]	0002808
Narrow chest	Low chest circumference Narrow shoulders [ more ]	0000774
Osteomyelitis	Bone infection	0002754
Splenomegaly	Increased spleen size	0001744
Percent of people who have these symptoms is not available through HPO
Abnormal thorax morphology	Abnormality of the chest	0000765
Abnormality of pelvic girdle bone morphology	Abnormal shape of pelvic girdle bone	0002644
Absent frontal sinuses		0002688
Autosomal recessive inheritance		0000007
Carious teeth	Dental cavities Tooth cavities Tooth decay [ more ]	0000670
Delayed eruption of permanent teeth	Delayed eruption of adult teeth	0000696
Delayed eruption of primary teeth	Delayed eruption of baby teeth Delayed eruption of milk teeth Late eruption of baby teeth Late eruption of milk teeth [ more ]	0000680
Hypodontia	Failure of development of between one and six teeth	0000668
Increased bone mineral density	Increased bone density	0011001
Micrognathia	Little lower jaw Small jaw Small lower jaw [ more ]	0000347
Osteolytic defects of the distal phalanges of the hand		0009839
Persistence of primary teeth	Delayed loss of baby teeth Failure to lose baby teeth Retained baby teeth [ more ]	0006335
Prominent nose	Big nose Disproportionately large nose Increased nasal size Increased size of nose Large nose Pronounced nose [ more ]	0000448
Prominent occiput	Prominent back of the skull Prominent posterior skull [ more ]	0000269
Scoliosis		0002650
Spondylolisthesis	Displacement of one backbone compared to another Slipped backbone [ more ]	0003302
Spondylolysis		0003304

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Do you have more information about symptoms of this disease? We want to hear from you.

Last updated: 2/1/2021

Cause Cause

Pycnodysostosis occurs when the CTSK gene is not working correctly.^[3] DNA changes known as pathogenic variants are responsible for making genes work incorrectly or sometimes, not at all.

Last updated: 6/8/2020

Inheritance Inheritance

Pycnodysostosis is inherited in an autosomal recessive pattern.^[3] All individuals inherit two copies of each gene. Autosomal means the gene is found on one of the numbered chromosomes found in both sexes. Recessive means that both copies of the responsible gene must be altered to have the condition.

People with autosomal recessive conditions inherit one alteration from each of their parents. The parents, who each have one gene alteration, are known as carriers. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected). When two carriers of an autosomal recessive condition have children, there is a 25% (1 in 4) chance to have a child with the condition.

Last updated: 6/8/2020

Diagnosis Diagnosis

Pycnodysostosis is diagnosed through a clinical examination, the symptoms, and X-rays of the affected bones. Genetic testing may be used to confirm the diagnosis.^[2]

Last updated: 6/8/2020

Testing Resources

The Genetic Testing Registry (GTR) provides information about the genetic tests for this condition. The intended audience for the GTR is health care providers and researchers. Patients and consumers with specific questions about a genetic test should contact a health care provider or a genetics professional.

Treatment Treatment

The treatment for pycnodysostosis is based on managing the symptoms. Treatment may include surgery, dental procedures, and medications for pain.^[2]^[3]

Specialists involved in the care of someone with pycnodysostosis may include:

Orthopedist
Dentist
Otolaryngologist
Orthodontist
Maxillofacial surgeon

Last updated: 6/8/2020

Statistics Statistics

There are about 200 reported cases of pycnodysostosis in the literature. It has been estimated that one to three people in 1,000,000 have pycnodysostosis. The exact number of people with this condition is unknown.^[2]^[4]^[5]

Last updated: 6/8/2020

Do you have updated information on this disease? We want to hear from you.

Find a Specialist Find a Specialist

If you need medical advice, you can look for doctors or other healthcare professionals who have experience with this disease. You may find these specialists through advocacy organizations, clinical trials, or articles published in medical journals. You may also want to contact a university or tertiary medical center in your area, because these centers tend to see more complex cases and have the latest technology and treatments.

If you can’t find a specialist in your local area, try contacting national or international specialists. They may be able to refer you to someone they know through conferences or research efforts. Some specialists may be willing to consult with you or your local doctors over the phone or by email if you can't travel to them for care.

You can find more tips in our guide, How to Find a Disease Specialist. We also encourage you to explore the rest of this page to find resources that can help you find specialists.

Healthcare Resources

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by the American College of Medical Genetics and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from MedlinePlus Genetics.

Related Diseases Related Diseases

Related diseases are conditions that have similar signs and symptoms. A health care provider may consider these conditions in the table below when making a diagnosis. Please note that the table may not include all the possible conditions related to this disease.

Conditions with similar signs and symptoms from Orphanet
Differential diagnoses include osteoporosis, osteopetrosis, cleidocranial dysplasia and idiopathic acroosteolysis (see these terms). Visit the Orphanet disease page for more information.

Research Research

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Patient Registry

The Lysosomal Disease Network is a team of doctors, nurses, research coordinators, and research labs throughout the U.S., working together to improve the lives of people with this condition through research. The Lysosomal Disease Network has a registry for patients who wish to be contacted about clinical research opportunities.

Learn More Learn More

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

The Monarch Initiative brings together data about this condition from humans and other species to help physicians and biomedical researchers. Monarch’s tools are designed to make it easier to compare the signs and symptoms (phenotypes) of different diseases and discover common features. This initiative is a collaboration between several academic institutions across the world and is funded by the National Institutes of Health. Visit the website to explore the biology of this condition.
Online Mendelian Inheritance in Man (OMIM) is a catalog of human genes and genetic disorders. Each entry has a summary of related medical articles. It is meant for health care professionals and researchers. OMIM is maintained by Johns Hopkins University School of Medicine.
Orphanet is a European reference portal for information on rare diseases and orphan drugs. Access to this database is free of charge.
PubMed is a searchable database of medical literature and lists journal articles that discuss Pycnodysostosis. Click on the link to view a sample search on this topic.

GARD Answers GARD Answers

Questions sent to GARD may be posted here if the information could be helpful to others. We remove all identifying information when posting a question to protect your privacy. If you do not want your question posted, please let us know.

Have a question? Contact a GARD Information Specialist.

References References

Farronato G, Salvadori S, Nolet F, Borgonovo A, Esposito L. Pycnodysostosis: review and case report. Minerva Stomatol. 2014; 63(6):229-237. https://pubmed.ncbi.nlm.nih.gov/25267152.
Bizaoui V, Michot C, Baujat G, et al. Pycnodysostosis: Natural history and management guidelines from 27 French cases and a literature review. Clin Genet. 2019; 96(4):309-316. https://pubmed.ncbi.nlm.nih.gov/31237352.
Gray ML, Su A, Cruciata G, Som PM. Pycnodysostosis in an Adult: A Case Report and Review of the Literature. Ear Nose Throat J. 2019; 98(10):627-628. https://pubmed.ncbi.nlm.nih.gov/31847556.
de Oliveira EM, de Arruda JAA, Nascimento PAM, Neiva IM, Mesquita RA, Souza LN. An Update on Osteomyelitis Treatment in a Pycnodysostosis Patient. J Oral Maxillofac Surg. 2018; 76(10):2136.e1-2136.e10. https://pubmed.ncbi.nlm.nih.gov/30030999.
Markatos K, Mavrogenis AF, Karamanou M, Androutsos G. Pycnodysostosis: the disease of Henri de Toulouse-Lautrec. Eur J Orthop Surg Traumatol. 2018; 28(8):1569-1572. https://pubmed.ncbi.nlm.nih.gov/29797092.
Khoja A, Fida M, Shaikh A. Pycnodysostosis with Special Emphasis on Dentofacial Characteristics. Case Rep Dent. 2015 Nov 16; https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4663328/.