Vitamin B6 Deficiency Anemia Attributed to Levodopa/Carbidopa Intestinal Gel Therapy for Parkinson's Disease: A Diagnostic Pitfall for Myelodysplastic Syndrome with Ring Sideroblasts

Vitamin B6 (VB6) is essential to heme synthesis, and its deficiency can lead to anemia. VB6 deficiency anemia is typically microcytic, hypochromic, and sideroblastic. VB6 deficiency is a well-recognized complication of levodopa/carbidopa therapy, as metabolism of levodopa to dopamine is VB6-dependent, and carbidopa irreversibly forms bonds and deactivates VB6. We herein report a 75-year-old man with advanced Parkinson's disease who developed severe VB6 deficiency anemia due to levodopa/carbidopa intestinal gel therapy. His anemia was promptly resolved with simple oral supplementation of pyridoxal phosphate hydrate. VB6 deficiency anemia can mimic myelodysplastic syndrome and thus is an important differential diagnosis for patients administered levodopa/carbidopa.