Lethal Kniest-like dysplasia

Lethal Kniest-like dysplasia (also known as lethal Kniest-like syndrome) is an extremely rare and severe skeletal dysplasia that presents at birth and is typically fatal in the neonatal period or shortly thereafter. It shares some clinical features with Kniest dysplasia but is distinguished by its lethal course. The condition primarily affects the skeletal system, with characteristic findings including severe shortening of the limbs (micromelia), a short trunk, a flat face with a depressed nasal bridge, and marked platyspondyly (flattened vertebral bodies). Radiographic features include dumbbell-shaped long bones, coronal clefts of the vertebral bodies, and significant metaphyseal abnormalities. Additional features may include cleft palate, respiratory insufficiency due to a small thorax, and ocular abnormalities. The disorder affects the development of cartilage and bone, leading to profound skeletal underdevelopment that is incompatible with sustained life. Histological examination of cartilage typically reveals characteristic abnormalities in the cartilage matrix, including a distinctive "Swiss cheese" appearance. The underlying molecular basis has not been fully elucidated in all reported cases, though some cases have been linked to defects in type II collagen or related extracellular matrix components. Due to the lethal nature of this condition, there are no curative treatments available. Management is supportive and palliative, focusing on comfort care for affected neonates. Genetic counseling is recommended for families with an affected child to discuss recurrence risks. Only a very small number of cases have been reported in the medical literature, making this one of the rarest forms of lethal skeletal dysplasia.

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