Pancytopenia is a reduction in red blood cells, white blood cells, and platelets. The document outlines an approach to evaluating a case of pancytopenia, including considering decreased bone marrow production, increased cell destruction, a thorough history and physical exam, and diagnostic tests like complete blood count, peripheral smear, and bone marrow aspiration and biopsy to determine the underlying cause. The causes of pancytopenia are grouped based on mechanism and include conditions like aplastic anemia, megaloblastic anemia, myelodysplastic syndrome, liver disease, and others.