Histologic sections showed a proliferation of eccrine ducts with an organoid architecture. No vascular abnormalities were seen.
The eccrine nevus is a rare entity with varying clinical manifestations. Microscopically, it consists of an increase in the size or number of mature eccrine secretory coils,1 as seen in our patient. This lesion is considered to be a hamartoma and must be differentiated from the eccrine angiomatous hamartoma, a similar lesion. Both show increased numbers of eccrine structures, but pure eccrine nevi lack the numerous capillary channels surrounding and intermingled with the eccrine structures that are found in eccrine angiomatous hamartomas.1 Fewer than 20 cases of pure eccrine nevi have been reported in the literature. Clinically, the lesion often presents as a localized hyperhidrotic area without other distinctive clinical features.2- 9 There have been reports of lesions presenting as depressed brownish hyperhidrotic patches10 and as brown hyperhidrotic plaques.11 Eccrine nevi that result in hyperhidrosis have been called localized unilateral hyperhidrosis,4,8,9nevus sudoriferous,5 and sudoriferous hamartoma.11 Other cases have been asymptomatic and have presented as skin-colored to slightly brown papules,12 depressed brownish patches,13 and centrally depressed nodules surrounded by a slightly scaly border.14 Our case is similar to that described by Imai and Nitto,12 which had groups of asymptomatic flesh-colored to light-brown papules in a linear distribution. Interestingly, many reported cases of eccrine nevi have occurred on the forearm,15 as did the lesion in our patient. Only 2 cases in the literature were reported to be congenital. Both involved areas of localized unilateral hyperhidrosis without other clinical features in adults who had had the lesions as long as they could remember.4 Several previously reported cases occurred during childhood and adolescence,3,5,10- 12 with the youngest of the patients developing the nevus at the age of 1 month.13 Our case is unusual in that, to the best of our knowledge, it is only the third case of a congenital eccrine nevus reported in the literature and the first of those to present with papules without hyperhidrosis. Eccrine nevi are harmless but may be surgically removed if so desired for cosmetic purposes.16
Grouped Papules on the Arm of an Infant. Arch Dermatol. 2000;136(4):547-552. doi: