Giant congenital melanocytic nevus with vascular malformation and epidermal cysts associated with a somatic activating mutation in BRAF.

Giant congenital melanocytic nevi may be symptomatically isolated or syndromic. Associations with capillary malformations are exceptional, and development of epidermal cysts has not been described. A 71-year-old patient with a giant congenital melanocytic nevus (CMN) of the lower back, buttocks, and thighs was asymptomatic except for unexpected hemorrhage during partial surgical excision years before. Blunt trauma at age 64 initiated recurrent, severe pain under the nevus; multiple large epidermal cysts then developed within it. Imaging and biopsy showed a large, non-pulsatile venous malformation intermingled with the deep nevus. A low-abundance, heterozygous BRAF c.1799T>A (p.V600E) mutation was present in both gluteal and occipital congenital nevi; additional mutations in NRAS, GNAQ, GNA11, HRAS, or PIK3CA were undetectable. This is the first demonstration of a recurrent BRAF mutation in multiple large congenital nevi from the same individual, confirming that this malformation can have multiple genetic origins. Early constitutive activation of BRAF can therefore cause unusual associations of giant nevi with vascular malformations, indicating that both pigment and endothelial cell physiology may be affected by mosaic RASopathies.

Widespread dynamic and pleiotropic expression of the melanocortin-1-receptor (MC1R) system is conserved across chick, mouse and human embryonic development.

BACKGROUND: MC1R, a G-protein coupled receptor with high affinity for alpha-melanocyte stimulating hormone (αMSH), modulates pigment production in melanocytes from many species and is associated with human melanoma risk. MC1R mutations affecting human skin and hair color also have pleiotropic effects on the immune response and analgesia. Variants affecting human pigmentation in utero alter the congenital phenotype of both oculocutaneous albinism and congenital melanocytic naevi, and have a possible effect on birthweight. METHODS AND RESULTS: By in situ hybridization, RT-PCR and immunohistochemistry, we show that MC1R is widely expressed during human, chick and mouse embryonic and fetal stages in many somatic tissues, particularly in the musculoskeletal and nervous systems, and conserved across evolution in these three amniotes. Its dynamic pattern differs from that of TUBB3, a gene overlapping the same locus in humans and encoding class III ß-tubulin. The αMSH peptide and the transcript for its precursor, pro-opiomelanocortin (POMC), are similarly present in numerous extra-cutaneous tissues. MC1R genotyping of variants p.(V60M) and p.(R151C) was undertaken for 867 healthy children from the Avon Longitudinal Study of Parent and Children (ALSPAC) cohort, and birthweight modeled using multiple logistic regression analysis. A significant positive association initially found between R151C and birth weight, independent of known birth weight modifiers, was not reproduced when combined with data from an independent genome-wide association study of 6,459 additional members of the same cohort. CONCLUSIONS: These data clearly show a new and hitherto unsuspected role for MC1R in noncutaneous solid tissues before birth.