The mask of deficiency: A rare case of facial hyperpigmentation in vitamin B12 deficiency - a case report and review of literature.

Vitamin B₁₂ deficiency can manifest in various forms, including skin changes in the form of hyperpigmentation. The hyperpigmentation in vitamin B₁₂ deficiency commonly presents over the hands and feet, but presenting over the face and oral cavity is very rare. Here we describe an interesting case where there was hyperpigmentation in the face and oral cavity which was mimicking Addison's disease, but the actual diagnosis was vitamin B₁₂ deficiency. This case stresses that knowing the uncommon manifestations of common disease is more important than knowing the common manifestations of uncommon disease.