Spondyloepimetaphyseal dysplasia, matrilin-3 type

Spondyloepimetaphyseal dysplasia, matrilin-3 type (SEMD matrilin-3 type) is a rare inherited skeletal disorder caused by mutations in the MATN3 gene, which encodes the matrilin-3 protein — an important component of cartilage extracellular matrix. This condition belongs to the broader group of spondyloepimetaphyseal dysplasias, which are characterized by abnormalities affecting the vertebrae (spondylo-), the ends of long bones (epi-), and the growing portions of long bones (metaphyseal). The skeletal system is primarily affected, leading to disproportionate short stature that typically becomes apparent in childhood. Key clinical features include short-limbed short stature, bowing of the lower extremities (genu varum), waddling gait, lumbar lordosis, and early-onset degenerative joint disease. Radiographic findings typically reveal platyspondyly (flattened vertebral bodies), irregular epiphyses, and metaphyseal abnormalities, particularly in the long bones of the legs. Hip involvement with dysplastic changes is common and may progress over time. Some patients may also develop joint pain and stiffness due to premature osteoarthritis. There is currently no cure or disease-specific treatment for SEMD matrilin-3 type. Management is supportive and symptomatic, focusing on orthopedic interventions to address limb malalignment, physical therapy to maintain joint mobility and muscle strength, pain management, and monitoring for progressive joint degeneration. Surgical procedures such as osteotomies or joint replacement may be considered in severe cases. Regular follow-up with orthopedic specialists and clinical geneticists is recommended to monitor skeletal complications and optimize quality of life.

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