Omodysplasia

Omodysplasia is a rare skeletal dysplasia characterized by severe shortening of the humeri and femora (the long bones of the upper arms and thighs), giving rise to a distinctive form of short-limbed dwarfism. The name derives from the Greek word 'omos' meaning shoulder, reflecting the prominent involvement of the proximal limbs. Two forms are recognized: an autosomal recessive form (also called major form) and an autosomal dominant form (also called minor form). The autosomal recessive form is more severe and is caused by mutations in the GPC6 gene, which encodes glypican 6, a cell-surface proteoglycan involved in growth factor signaling. The autosomal dominant form is generally milder and primarily affects the upper limbs. Key clinical features include rhizomelic limb shortening (predominantly affecting the proximal segments), characteristic facial features such as a flat face, frontal bossing, depressed nasal bridge, and a long philtrum. Patients may also exhibit limited elbow extension, dislocated radial heads, and short first metacarpals. In the recessive form, additional features can include genital anomalies (cryptorchidism in males), congenital heart defects, and more pronounced craniofacial dysmorphism. Radiographic findings are distinctive and include short, broad humeri and femora with abnormal metaphyseal flaring and delayed skeletal maturation. There is no specific cure or targeted therapy for omodysplasia. Management is supportive and multidisciplinary, involving orthopedic care for skeletal complications, monitoring for cardiac anomalies, and developmental support as needed. Growth hormone therapy has not been shown to be effective. Surgical interventions may be considered for joint contractures or limb length discrepancies. Genetic counseling is important for affected families to understand recurrence risks based on the specific inheritance pattern identified.

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