A 75-year-old woman lives alone and eats sparingly because of her low fixed retirement income. For the past 2 weeks, she has noticed pain in her right leg. On physical examination, there is marked tenderness to palpation over the lateral aspect of the right shin, a poorly healed cut on the right hand, and a diffuse hyperkeratotic skin rash. A radiograph shows a right tibial diaphyseal subperiosteal hematoma. Laboratory studies show a hemoglobin level of 11.3 g/dL. A deficiency of which of the following nutrients is most likely to explain these findings?

Signs and symptoms of scurvy can be subtle. The diet must contain a constant supply of vitamin C (ascorbic acid) because none is produced endogenously. Older individuals with an inadequate diet are as much at risk as younger individuals. Folate deficiency can lead to anemia, but it does not cause capillary fragility with hematoma formation or skin rash. Niacin deficiency can lead to an erythematous skin rash in sun-exposed areas, but not to anemia. Riboflavin deficiency can lead to findings such as glossitis, cheilosis, and neuropathy. Vitamin A deficiency can produce a skin rash, but it does not cause anemia. Vitamin K is important in maintaining proper coagulation, but a deficiency state is not associated with anemia or skin rash.