Dementia, diarrhea, desquamating shellac-like dermatitis revealing late-onset cobalamin C deficiency

MMA: methylmalonic acid CASE REPORT We present a case of late-onset cobalamin C deficiency presenting with a unique shellac-like erosive desquamation and mental status changes that was dramatically responsive to treatment. We discuss cobalamin C deficiency and compare the cutaneous findings with other similar nutritional deficiency states. The brown shellac-like desquamation should prompt dermatologists to consider this diagnosis in the setting of a suspected nutritional deficiency. A 21-year-old wheelchair-bound man with a history of autoimmune cerebritis, seizure disorder, and recurrent deep-vein thrombosis presented with intractable diarrhea and an acute and progressive reduction in mentation. The patient was previously able to use minimal verbal communication, but upon admission, he was somnolent. Three years prior, he was much more independent, working at a fast-food chain. Patient had been stable taking home medications, which included lacosamide, levetiracetam, topiramate, phenobarbital, diazepam, clobazam, warfarin, escitalopram, and mirtazapine. On previous admission for nonconvulsive status epilepticus, the patient was found to have hyperammonemia. At that time, urine organic acids revealed an elevated lactic acid 128 mg/dL (reference range 0-50 mg/dL) and methylmalonic acid (MMA) 2463 mg/dL (reference range 0-5 mg/dL). These findings suggested a methylmalonic acidemia, although no further testing was performed. On this admission, causes of altered mentation were extensively investigated