Syndactyly type 8

Syndactyly type 8, also known as metacarpal 4-5 fusion (MF4), is a rare congenital limb malformation characterized by fusion (synostosis) of the fourth and fifth metacarpal bones in the hands. This condition is present at birth and primarily affects the skeletal structure of the hands. Affected individuals typically have shortened fourth and fifth fingers (brachydactyly) due to the bony fusion of the metacarpal bones, which may limit hand function and grip to varying degrees. The fusion is typically bilateral, affecting both hands symmetrically. The condition is inherited in an autosomal dominant pattern, meaning that a single copy of the altered gene from one parent is sufficient to cause the disorder. Syndactyly type 8 has been linked to mutations in the FGF16 gene on the X chromosome in some families, though the genetic basis may be heterogeneous. Unlike many other forms of syndactyly that involve soft tissue webbing between the fingers, this type is distinguished by its bony fusion of the metacarpal bones rather than cutaneous or osseous fusion of the digits themselves. There is no specific cure for syndactyly type 8. Management is primarily supportive and may include orthopedic evaluation and, in some cases, surgical intervention to improve hand function if the fusion significantly impairs daily activities. Occupational therapy may also be beneficial. The condition is generally non-progressive, and many affected individuals maintain adequate hand function throughout life. Genetic counseling is recommended for affected families to discuss recurrence risks and inheritance patterns.

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