Skin Hyperpigmentation as Initial Manifestation of Vitamin B12 Deficiency: A Case of Delayed Diagnosis With Late-Onset Subacute Combined Degeneration of the Cord.

Vitamin B12 deficiency may present with a myriad of symptoms. Rarely, skin hyperpigmentation may be the sole initial manifestation of this micronutrient deficiency, which can easily be overlooked, leading to delayed diagnosis. This case report describes a 32-year-old Ghanaian male who presented with a 4-year history of progressive darkening of the dorsal aspects of the interphalangeal joints of both hands, the palms, and soles of the feet, for which he did not seek immediate medical attention. He later developed a worsening unsteady gait. Neurological assessment revealed mild weakness in both lower limbs, brisk knee reflexes, diminished ankle reflexes, and bilateral extensor plantar reflexes. Additionally, he had decreased sensitivity to fine touch, impaired proprioception, and diminished vibration sense. His gait was ataxic with a positive Romberg's sign. Laboratory investigations showed macrocytosis with anemia and a markedly reduced serum vitamin B12 level. Upper gastrointestinal endoscopy with biopsy identified chronic gastritis. He was diagnosed with vitamin B12 deficiency secondary to chronic gastritis complicated by subacute combined degeneration of the cord. Following parenteral repletion of vitamin B12, the skin hyperpigmentation completely resolved. His neurological symptoms also significantly improved. This case report highlights the need to recognize skin hyperpigmentation as a potential initial symptom of cobalamin deficiency, which is critical for early diagnosis and prompt initiation of treatment to prevent debilitating neurological complications.