Abstract
We report two cases of rudimentary polydactyly seen on the little fingers of a 3-year-old girl and a 4-month-old boy. Both lesions were 3 mm in size, of normal skin color and in Case 1, was accompanied by tenderness. Histopathologically, both lesions showed epidermal changes of hyperkeratosis, hypergranulosis and acanthosis with an elongation of rete ridges. In the dermis, longitudinal sections of nerve fiber bundles aligning perpendicularly to the epidermis were seen extending from the papillary dermis to the deep dermis. In Case 1, a large number of Meissner bodies were present in the papillary dermis and cross-sectioned nerve fiber bundles were seen in abundance in the deep dermis. In Case 1, a weak reaction for S-100 protein was observed in Meissner bodies and nerve fibers, while a strong positive reaction for the neurofilament was observed in some nerve fibers. Electron microscopic findings in Case 1 showed the presence of abundant Merkel cells and axons in the basal layer, Luse bodies within and surrounding Meissner bodies, and a large number of Schwann cells, myelinated and non-myelinated nerves in the papillary dermis of the lesion. There has been no previous report on this rare disorder of rudimentary polydactyly of the little fingers in Japan.
