Kniest dysplasia

Kniest dysplasia (also known as Kniest syndrome or metatropic dwarfism type II) is a rare skeletal disorder belonging to the group of type II collagenopathies. It is caused by mutations in the COL2A1 gene, which encodes type II collagen, a critical structural protein found in cartilage, the vitreous humor of the eye, and the inner ear. The condition is characterized by disproportionate short stature (short trunk dwarfism), a flat face with prominent eyes, enlarged and stiff joints (particularly the knees), and a short trunk with kyphoscoliosis. Skeletal abnormalities are typically apparent at birth, with affected individuals often presenting with a short trunk, shortened limbs, and a characteristic "Swiss cheese" appearance of cartilage on histological examination. Kniest dysplasia affects multiple body systems beyond the skeleton. Ocular complications are common and include severe myopia, vitreoretinal degeneration, and retinal detachment, which can lead to significant visual impairment or blindness if untreated. Sensorineural and/or conductive hearing loss is frequently observed and may be progressive. Affected individuals may also experience recurrent otitis media, cleft palate, and respiratory difficulties in infancy due to tracheomalacia or a small chest. Joint contractures and progressive joint enlargement can significantly limit mobility, and early-onset osteoarthritis is common. Intelligence is typically normal. There is currently no cure for Kniest dysplasia, and management is supportive and multidisciplinary. Treatment focuses on orthopedic interventions for joint contractures and skeletal deformities, ophthalmologic monitoring and treatment to prevent vision loss, audiologic assessment and hearing aids as needed, and management of respiratory complications. Physical therapy plays an important role in maintaining joint mobility. Regular surveillance by a team including orthopedists, ophthalmologists, audiologists, and pulmonologists is recommended to address complications as they arise.

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