in human physiology, any of the isolated anomalies of the digits (fingers or toes) in an otherwise normal individual or as one symptom of a more generalized genetic abnormality. In polydactyly, having more than the normal number of digits, the extra digit is smaller than normal and usually at the outside of the hand or foot; it may be removed surgically. Polydactyly sometimes also occurs in various genetic syndromes, including the Ellis–van Crevald syndrome and chromosomal trisomy 13 (D₁-trisomy). In syndactyly the digits are fused or webbed, and it also is treated surgically. Syndactyly is a common finding in many genetic disorders. Brachydactyly, or abnormally short digits, may result from underdevelopment or absence of some of the phalanges or metacarpals and metatarsals. Long, spidery digits (arachnodactyly) are typical in Marfan's syndrome (Marfan syndrome).