Vitamin B12 deficiency results in neuropsychiatric, hematologic, gynecologic, cardiovascular, and cutaneous manifestations. It is seen most commonly in the elderly, malabsorption diseases？？(>60% of all cases), vegans, and vegetarians. Manifestations of pernicious anemia may be similar to Addison disease and may lead to a misdiagnosis. Herein, we report two cases of vitamin B12 deficiency in which clinical features shared many similarities with Addison disease. Both patients presented with progressive darkening of hands and postural hypotension that reversed with replenishment of vitamin B12. Vitamin B12 deficiency should be considered in patients presenting with skin lesions especially with other coexisting autoimmune diseases. 1. Introduction Vitamin B12 is a water soluble vitamin, present in various forms: cyanocobalamin (vitamin B12), hydroxocobalamin (vitamin B12a), aquacobalamin (vitamin B12b), nitritocobalamin (vitamin B12c), 59-deoxyadenosylcobalamin (coenzyme B12), and methylcobalamin (methyl B12). Its deficiency is a major health issue and a major diagnostic challenge; its presentation varies from being asymptomatic to affecting multiple organ systems. Some of the better studied and better known manifestations are hematologic such as macrocytic anemia, pancytopenia and neurological, such as orthostatic hypotension, paraesthesias, and abnormal gait [1, 2]. Some of the lesser known manifestations are cutaneous such as skin hyperpigmentation, stomatitis, and hair and nail changes. These may be important to recognize as early treatment may prevent potentially irreversible complications. 2. Case Presentation 2.1. Case 1 A 40-year-old African American woman with history of myasthenia gravis, Hashimoto’s thyroiditis stable on thyroxine replacement, and childhood asthma was seen in the outpatient clinic for numerous complaints including fatigue, multiple syncopal episodes, and diffuse darkening of the palms of both hands for the past 3 to 4 months. There was no rash or dermatitis preceding the onset of hyperpigmentation. She is a nonvegetarian and reports occasional alcohol use but no smoking or illicit drugs. She has a family history of type 2 diabetes mellitus, heart disease, hypertension, autoimmune disorders, and hypothyroidism. Physical examination showed a well-developed woman in no distress. Her blood pressure was 113/88 sitting, 105/76 standing, temperature of 37° Celsius, pulse of 92 (sitting), 112 beats/minute (standing), and respiratory rate of 16 breaths/minute. She had pale mucus membranes. The respiratory, cardiovascular, neurological,
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