Melanoderma: uncommon presentation of a common condition

A 64-year-old man presented with blackish pigmentation of skin and tongue for more than 2 years that did not improve with local remedies. He had no history of comorbid medical or surgical illnesses. General examination showed severe hyperpigmentation of skin and mucosa and also showed anaemia. Systemic examination was unremarkable except for Romberg sign and mild hyperreflexia. Adrenal insufficiency was ruled out by normal cortisol levels and haemogram showed macrocytosis with hypersegmented neutrophils suggestive of severe vitamin B12 deficiency which confirmed by low serum B12 levels. After 3 months of parenteral vitamin B12 treatment, the pigmentation and anaemia improved significantly. The mechanism of hyperpigmentation due to B12 deficiency is postulated to be increased melanin deposition in the basal layer of the epidermis. Since vitamin B12 deficiency is not uncommonly encountered in general practice, atypical presentation of this easily diagnosable and treatable condition is emphasised.

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