Recognizing Subacute Combined Degeneration in Patients With Normal Vitamin B12 Levels

Vitamin B12 deficiency is commonly associated with dementia in patients over the age of 65 years; however, it can affect people of all ages. Recognizing the clinical sequelae of subacute combined degeneration is essential for the timely diagnosis and treatment of vitamin B12 deficiency. In this report, we describe a case of a young man presenting with several months of neuropathy, depression, and abdominal symptoms. His initial vitamin B12 levels were within normal limits, but an elevated methylmalonic acid level and subacute combined degeneration of his spine on MRI confirmed the diagnosis of vitamin B12 deficiency. The patient later tested positive for autoantibodies associated with pernicious anemia. His symptoms improved with intramuscular injections of cyanocobalamin. This case highlights the importance of recognizing vitamin B12 deficiency in patients of all age groups even in the setting of apparently "normal" B12 levels.