A 44 year-old male arrives in the emergency room, complaining of ‘bone pains’, severe weakness and fatigue, easy bruising in the skin, gingival bleeding, nose bleeds, shortness of breath and vision change. On review of systems, you notice continuous headaches and weight loss of over 20 pounds in two months. He was also treated for three episodes of ‘sinusitis’ in the last 2 months. On a physical examination, you notice a thin young man who appears pale, confused and distressed due to dyspnea. His gums are swollen. Other remarkable things are hepatomegaly, lymphadenopathy and tenderness over the sternum, right tibia and left femur. Suspecting a serious underlying disorder, you ordered some laboratory tests. Bone marrow film showed most cells with cytoplasmic reddish-purple granules with several long slender inclusions (as shown in the image), highlighted by peroxidase stain and some lymphocytes are compressed among the cells. Patient is diagnosed with acute promyelocytic leukemia. The acid form of which of the following vitamins is used to treat acute promyelocytic leukemia?
