Spondyloepimetaphyseal dysplasia, aggrecan type

Spondyloepimetaphyseal dysplasia, aggrecan type (SEMD aggrecan type), also known as SEMD Kimberley type or aggrecan-related spondyloepimetaphyseal dysplasia, is a rare inherited skeletal disorder caused by mutations in the ACAN gene, which encodes aggrecan, a major proteoglycan component of cartilage. Aggrecan plays a critical role in cartilage structure and function, particularly in providing resistance to compression in joints and growth plates. Mutations in this gene disrupt normal cartilage and bone development, leading to characteristic skeletal abnormalities. The condition primarily affects the skeletal system, with involvement of the spine (spondylo-), the ends of long bones (epiphyses), and the growth plate regions (metaphyses). Key clinical features include disproportionate short stature, which typically becomes apparent in early childhood, along with short limbs, brachydactyly (short fingers), midface hypoplasia, and early-onset degenerative joint disease (osteoarthritis). Radiographic findings may include platyspondyly (flattened vertebral bodies), irregular epiphyses, and widened or irregular metaphyses. Affected individuals may also develop lumbar lordosis and genu varum (bowed legs). There is currently no cure or disease-specific treatment for SEMD aggrecan type. Management is supportive and symptomatic, focusing on orthopedic monitoring, pain management, physical therapy, and surgical intervention when necessary for joint complications or skeletal deformities. Growth hormone therapy has been explored in some aggrecan-related short stature conditions, though its efficacy specifically in SEMD aggrecan type requires further study. Regular follow-up with a multidisciplinary team including clinical geneticists, orthopedic specialists, and rheumatologists is recommended.

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