Knuckle Pigmentation as an Early Cutaneous Sign of Vitamin B12 Deficiency: A Case Report

Vitamin B12 deficiency can present with variable hematological, neuropsychiatric, and mucocutaneous changes. Hyperpigmentation, specifically involving the knuckles has been described in vitamin B12 deficiency, but usually,these patients are symptomatic with systemic manifestations like megaloblastic anemia, pancytopenia, or neurological deficits. Here, we are reporting a case of nutritional vitamin B12 deficiency, who presented with isolated knuckle pigmentation and was successfully treated with oral therapy. This case also highlights the importance of recognizing this cutaneous sign as an early marker of vitamin B12 deficiency; thereby enabling the clinician to treat the disease before it leads to irreversible neurological complications.