A Case of Cobalamin Deficiency and Macrocytic Anemia Secondary to Sunitinib.

Sunitinib is an oral tyrosine kinase inhibitor (TKI) commonly used in the treatment of renal cell carcinoma (RCC). Among a broad range of toxicities, anemia and macrocytosis are common in patients treated with sunitinib. Correlation between sunitinib-associated macrocytosis and cobalamin deficiency has been reported in small case series and retrospective analyses, although others have not found an association. Here, we present a case of transfusion-dependent macrocytic anemia with cobalamin and folate deficiency in a patient with RCC treated with sunitinib.