Unusual Cutaneous and Mucosal Manifestations of Neonatal Inflammatory Skin and Bowel Disease Type 1 due to a Novel Homozygous <i>ADAM17</i> Mutation

Neonatal inflammatory skin and bowel isease type 1 (NISBD1) is a rare autosomal recessive genodermatosis caused by pathogenic variants in ADAM17, a gene essential for epithelial development and cytokine regulation. Affected individuals typically present during infancy with severe cutaneous inflammation, recurrent infections, fragile hair, and variable gastrointestinal involvement. We report a 4-year-old girl with an unusual constellation of mucocutaneous manifestations associated with a novel homozygous ADAM17 mutation (c.436G>A; p.Gln146Lys), thereby expanding the known phenotypic spectrum of NISBD1. This case highlights atypical NISBD1 features, including pyoderma gangrenosum-like ulcerations, pyostomatitis-like mucosal involvement, annular atrophic scarring, and absence of bowel disease.