Expert Opinion :
This child has presented with progressive pancytopenia. Thus, one may suspect aplastic anemia, hemophagocytosis, and leukemia as possible causes. Aplastic anemia may be likely as the child does not have hepatosplenomegaly or lymphadenopathy. However, children with aplastic anemia usually do not have this waxing-waning of platelet count and red cells tend to decrease earlier. In this child, neutrophils were the predominant cell line to be affected. Neutropenia and thrombocytopenia may be seen with viral infection which can cause bone marrow suppression. However, in this child, most of the viral markers such as HIV, Dengue, CMV and EBV were negative. The important part in the history is the waddling gait in the child with a painful left hip. Though X-Rays of the limbs and ultrasound were normal, bone involvement may still be present and can only be detected by bone scan. Leukemia can present with bone pains and pancytopenia. With infiltration of leukemic cells in the marrow, the normal WBC, red cells and platelets tend to disappear leading to pancytopenia. A peripheral smear after 15 days showed presence of blast cells (100%) and the child was diagnosed as leukemia.