Development of Dysplastic Nevi in a Child with LEPR Deficiency Treated with Setmelanotide.

Setmelanotide is a recently approved medication for patients over two years of age with monogenic obesity that emerges from POMC, LEPR, PCSK1 mutations, or Bardet-Biedl syndrome. While primarily targeting melanocortin-4 receptors (MC4R), setmelanotide also weakly stimulates melanocortin-1 receptors (MC1R), which may affect pigmentation. Clinical outcomes of this treatment modality remain limited due to the rarity of disorders mentioned above. We present a 12-year-old boy with a homozygous LEPR mutation who experienced skin hyperpigmentation shortly after the initiation of setmelanotide treatment. By the third month of treatment, gradual darkening of nevi was noted. At six-month follow-up, two nevi were excised due to pigmentation changes, and histopathology revealed dysplastic features in both. This case raises concerns about potential MC1R-mediated melanocytic activity during setmelanotide treatment. Therapy was temporarily discontinued. To our knowledge, this is the first reported pediatric case with LEPR-related monogenic obesity developing dysplastic nevi during setmelanotide use.