Small and intermediate-sized congenital melanocytic nevi (CMN) are relatively common birthmarks, occurring in approximately 1% of the population. The presence of small CMN as a familial trait has seldom been reported.1 We describe two families in which a grandparent and grandchild each had an intermediate-sized congenital melanocytic nevus at the identical site on the body.
Report of Cases.
Case 1. An 8-month-old infant was referred for evaluation of an intermediate-sized congenital melanocytic nevus present on the right forearm, without significant change since birth. The family of this infant was particularly concerned about this birthmark because her 47-year-old maternal grandmother had a CMN located in the identical location since birth. Shortly after the birth of her granddaughter, the grandmother's nevus began to change in color and become more elevated (Figure). This lesion, measuring 3X2.8 cm, was excised and found to be a malignant melanoma, Clark's level 2, invasive to 0.4
Frieden IJ, Williams ML. Familial Site-Specific Congenital Melanocytic Nevus: Report of Two Families. Arch Dermatol. 1994;130(8):1075-1076. doi:10.1001/archderm.1994.01690080145029