Adult-onset melanonychia in Indian patients: A comprehensive narrative review

Melanonychia, defined as a brown-to-black pigmentation of the nail apparatus, most frequently presents as a longitudinal band (melanonychia striata), although diffuse (total) or transverse presentations also occur. This pigmentation results from either melanocytic activation or proliferation. Although frequently benign, melanonychia may also be the first sign of subungual melanoma (SUM). In Indian skin, melanonychia (racial/ethnic) is relatively common; however, there is an increasing concern amongst patients regarding the possibility of a malignancy. This review provides a detailed analysis of adult-onset melanonychia in Indian patients, highlighting its aetiology, clinical and onychoscopic features, diagnostic approach, histopathology, molecular genetics, management and prognosis in the Indian context. It includes a narrative synthesis of published literature, including Indian case series and other published literature, while focusing on coloured skin. In Indian adults (pigmented skin types), benign longitudinal melanonychia, often constitutional or reactive, is common; however, SUM, though rare, remains a serious differential. Diagnosis must integrate history, complete nail examination, onychoscopy, photographic monitoring and a low threshold for nail-matrix biopsy in suspicious cases. Molecular profiling indicates that SUM in Asian populations often harbours KIT (KIT proto-oncogene, receptor tyrosine kinase) or guanine nucleotide-binding protein, alpha Q polypeptide (GNAQ) mutations rather than the classical BRAF/NRAS (v-raf murine sarcoma viral oncogene homolog B/ neuroblastoma RAS viral oncogene homolog) mutations seen in sun-exposed melanomas. While the majority of melanonychia in Indian adults is benign, careful evaluation and awareness of red-flag features are essential to permit an early detection of melanoma. A structured diagnostic algorithm and clinician awareness are important for efficient management.