My Instructive Nail Case

In this informative session, the speaker discusses a clinical case involving a 62-year-old black male referred by a dermatologist due to concerns of potential melanoma. The patient has a long-standing, stable, dark brown longitudinal stripe on his right third fingernail, with a history of melanoma 15 years prior. Upon examination, the stripe is found to be rough rather than smooth, prompting further investigation with dermatoscopy, which reveals specific features that help differentiate between possible conditions. A biopsy is performed, resulting in a diagnosis favoring onychocytic matricoma, a rare benign nail matrix condition first described a little over a decade ago. The speaker emphasizes the importance of recognizing this condition amidst other differential diagnoses, including melanoma and various carcinomas. Several illustrative cases are shared to highlight the distinct presentations of onychocytic matricoma, including differences in pigmentation and texture. The presentation concludes with a reminder for dermatologists to consider this diagnosis when observing longitudinal melanonychia, especially in cases with associated thickening.