Isolated split hand-split foot malformation

Isolated split hand-split foot malformation (SHFM), also known as ectrodactyly or lobster-claw deformity, is a rare congenital limb malformation characterized by a deep median cleft in the hands and/or feet, absence of central digits (fingers or toes), and fusion (syndactyly) of the remaining digits. The condition results from a failure of normal development of the central rays of the hands and feet during embryonic limb formation. The severity is highly variable, even within the same family — some individuals may have only mild foot involvement while others have significant bilateral hand and foot malformations. The term 'isolated' distinguishes this condition from syndromic forms where split hand-split foot occurs alongside other anomalies such as intellectual disability, ectodermal dysplasia, or craniofacial abnormalities. SHFM is genetically heterogeneous, with multiple loci identified. The most common form, SHFM1 (OMIM 183600), is associated with rearrangements involving chromosome 7q21.2-q21.3, including the DLX5 and DLX6 genes. Other loci include SHFM3 (OMIM 246560) linked to duplications at 10q24, SHFM4 (OMIM 605289) caused by mutations in TP63, SHFM5 (OMIM 606708) at 2q31, and SHFM6 (OMIM 225300) caused by mutations in WNT10B with autosomal recessive inheritance. An X-linked form (SHFM2, OMIM 313350) has also been described. Reduced penetrance and variable expressivity are common features across all genetic subtypes. There is no cure for SHFM, and management is primarily supportive and functional. Treatment depends on the severity of the malformation and may include orthopedic surgery to improve hand or foot function, prosthetic devices, physical and occupational therapy, and adaptive aids. Early intervention can significantly improve functional outcomes. Genetic counseling is recommended for affected individuals and families to discuss recurrence risks and the variable nature of the condition.

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