Opsismodysplasia

Opsismodysplasia is an extremely rare skeletal dysplasia characterized by a severe delay in bone maturation (ossification), particularly affecting the long bones, vertebral bodies, and hands and feet. The name derives from the Greek word 'opsismos' meaning 'late,' reflecting the hallmark delayed ossification. This condition is caused by biallelic pathogenic variants in the INPPL1 gene (also known as SHIP2), which encodes a phosphatase involved in signaling pathways important for bone development. Clinical features are typically apparent at birth or prenatally and include severe short stature with short limbs (micromelia), a large anterior fontanelle, prominent forehead, depressed nasal bridge, and relatively short hands and feet with characteristic squared metacarpals and phalanges on radiographs. Radiographic findings are distinctive and include marked delay in epiphyseal ossification, platyspondyly (flattened vertebral bodies), and metaphyseal cupping. Affected infants may also present with respiratory difficulties and recurrent respiratory infections. Opsismodysplasia can follow a severe course, with some affected individuals dying in infancy or early childhood due to respiratory complications. However, milder cases with longer survival have been reported. There is no specific curative treatment; management is supportive and multidisciplinary, focusing on respiratory care, orthopedic monitoring, nutritional support, and developmental follow-up. Genetic counseling is recommended for affected families.

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