O06 Complete spontaneous resolution of NRAS-mosaic multiple congenital melanocytic naevi: proof of principle for therapeutic mole reversal.

Abstract

We present a unique case of complete spontaneous resolution of multiple congenital melanocytic naevi (CMN) with 17 years of photographic, histological and genetic evidence. This case is of biological importance as proof of principle that CMN are not permanent malformations, but rather potentially-reversable lesions. In turn, this proof of principle is of clinical importance, as the increased risk of melanoma development should have disappeared with the naevi. This process was happening to all lesions simultaneously and some of the smaller naevi had already disappeared. There was no history of injury, and at no point was there any sign of a halo, or of vitiligo, or of inflammation. At the age of two she had resection of the neuroid nodule as it was catching on clothes, and histology confirmed CMN with neuroid differentiation. Genetic testing of this sample demonstrated the commonest cause of CMN, a mosaic variant in NRAS (NM_002524.5 c.181C>A, p.(Q61K)). By the age of 13 there was remarkably little of any of the CMN to be seen or felt, and only some increased skin markings and a softness and slight laxity palpable in the skin of the upper back. However she was still shaving the posterior neck every 6 months for hypertrichosis. At the age of 17 she consented to a biopsy for research from this area which no longer needed shaving. This demonstrated a total absence of naevus cells, and NRAS sequencing by the most sensitive diagnostic methods currently available was normal.