My wife has a low platelet count and a high mcv - what condition could these symptoma diagnose?

Vitamins, EtOH, et a: An elevated MCV (mean reb blood cell size) is usually related to deficiency of vit B12 and/or folate (folic acid). Low platelet count may indicate drug effect on the bone marrow, bleeding, or platelet destruction. The combination of these two is seen in chronic alcohol use, or - more seriously- may indicate early myelodysplasia (a bone marrow disorder). In part, the answer depends upon age...

Finish workup: A platelet count slightly out of the reference range is of little concern, but assuming that the other indices support true macrocytosis (and not just 2 red cells counted as one), i'm concerned. If your wife uses any alcohol, ask her to think about stopping now. B12, folate, (folic acid) perhaps a reticulocyte count, and of course a look at the smear will get you a timely answer that may save her life.