Two major forms of thanatophoric dysplasia have been described, type I and type II. Type I thanatophoric dysplasia is distinguished by the presence of curved thigh bones and flattened bones of the spine (platyspondyly). Type II thanatophoric dysplasia is characterized by straight thigh bones and a moderate to severe skull abnormality called a cloverleaf skull.[1]
The Human Phenotype Ontology (HPO) provides the following list of features that have been reported in people with this condition. Much of the information in the HPO comes from Orphanet, a European rare disease database. If available, the list includes a rough estimate of how common a feature is (its frequency). Frequencies are based on a specific study and may not be representative of all studies. You can use the MedlinePlus Medical Dictionary for definitions of the terms below.
| Signs and Symptoms | Approximate number of patients (when available) |
| Abnormality of the femur | 90% |
| Abnormality of the metaphyses | 90% |
| Abnormality of the sacroiliac joint | 90% |
| Aplasia/Hypoplasia of the lungs | 90% |
| Bowing of the long bones | 90% |
| Brachydactyly syndrome | 90% |
| Cognitive impairment | 90% |
| Cutis laxa | 90% |
| Depressed nasal bridge | 90% |
| Increased nuchal translucency | 90% |
| Macrocephaly | 90% |
| Malar flattening | 90% |
| Micromelia | 90% |
| Muscular hypotonia | 90% |
| Narrow chest | 90% |
| Platyspondyly | 90% |
| Respiratory insufficiency | 90% |
| Short stature | 90% |
| Short thorax | 90% |
| Skeletal dysplasia | 90% |
| Small face | 90% |
| Split hand | 90% |
| Abnormality of neuronal migration | 50% |
| Frontal bossing | 50% |
| Hearing impairment | 50% |
| Intrauterine growth retardation | 50% |
| Kyphosis | 50% |
| Polyhydramnios | 50% |
| Proptosis | 50% |
| Ventriculomegaly | 50% |
| Abnormality of the kidney | 7.5% |
| Acanthosis nigricans | 7.5% |
| Atria septal defect | 7.5% |
| Cloverleaf skull | 7.5% |
| Hydrocephalus | 7.5% |
| Joint hypermobility | 7.5% |
| Limitation of joint mobility | 7.5% |
| Low-set, posteriorly rotated ears | 7.5% |
| Patent ductus arteriosus | 7.5% |
| Seizures | 7.5% |
| Autosomal dominant inheritance | - |
| Decreased fetal movement | - |
| Flared metaphysis | - |
| Heterotopia | - |
| Hypoplastic ilia | - |
| Intellectual disability, profound | - |
| Lethal short-limbed short stature | - |
| Metaphyseal irregularity | - |
| Neonatal death | - |
| Severe platyspondyly | - |
| Severe short stature | - |
| Short long bone | - |
| Short ribs | - |
| Short sacroiliac notch | - |
| Small abnormally formed scapulae | - |
| Small foramen magnum | - |
| Wide-cupped costochondral junctions | - |
Making a diagnosis for a genetic or rare disease can often be challenging. Healthcare professionals typically look at a person’s medical history, symptoms, physical exam, and laboratory test results in order to make a diagnosis. The following resources provide information relating to diagnosis and testing for this condition. If you have questions about getting a diagnosis, you should contact a healthcare professional.
The resources below provide information about treatment options for this condition. If you have questions about which treatment is right for you, talk to your healthcare professional.
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I was pregnant with twins who were diagnosed with thanatophoric dysplasia. What are the chances that I will have another pregnancy affected by this condition? See answer
