A Rare Syndrome of Five Finger Hands and Polydactyly of the Feet: A Case Report

Pashayan et al reported a familial syndrome in a father and his daughter that the daughter had bilateral five finger hands, absent thumbs, bilateral tibial aplasia, and preaxial polydactyly of the feet. Her father hands were identical to his affected daughter with five finger hands and no thumbs [3]. Borg et al have reported a case of tetramelic mirror-image polydactyly with unilateral tibial hypoplasia [4]. Lamb et al reported a kindred of 15 individuals in five generation with absent thumbs, five finger hands, partial or complete tibial absence and preaxial polydactyly [5]. The symmetric abnormalities in the hands and feet of the above reports suggest an autosomal dominant gene cause to the development of the four limbs. However, the authors of the above reports did not point to the exact genetic abnormality [3–5]. Kondoh et al and Kim et al have suggested a novel gene disrupted at a 14q13 breakpoint of t(2;14) which produces mirror-image polydactyly of hands and feet [6, 7]. However, the genetic abnormality might have variable expressivity to produce absent thumb, preaxial polydactyly of the hands and feet, and with or without varying degree of tibia aplsia

The embryonic limb buds development through proximodistal, radioulnar and dorsoventral axes. Proximodistal development depends on the apical ectodermal ridge (AER) signals. Radioulnar development depends on the morphogenic signals from the zone of polarizing activity (ZPA) located at the posterior border of the limb. AER and ZPA signals constitute a reciprocal feedback loop [8].

One explanation for the abnormalities of the limbs in this case might be that the genetic abnormality altered the AER and ZPA the activities [8]. Failure of the signals to reach the preaxial side from the AER leads to abort the development on the preaxial side of the feet and produce absence of the thumbs in the hands [8]. Ectopic ZPA morphogenic signals on the preaxial side of the limbs lead to produce five-fingered hands and mirror feet anomalies [8]. In hand ectopic ZPA signals on the radial side of the index finger produce finger duplication [9].

Al-Qattan et al have indicated that the phenotype of the mirror hand deformity is variable and patients may have absent thumbs, preaxial polydactyly and a hypoplastic radius. The presence of hypoplastic radius in the current case supports that the case may well be a variant of mirror hand [1].

In this case, the anomalies might be a rare syndrome of atypical mirror hands and mirror feet. This case is presented because of its rare occurrence and each reported case will hopefully bring more insight to the congenital anomalies.