Mononucleosis is sometimes mistaken for acute leukemia.
Severe aplastic anemia
Acute leukemia sometimes starts as severe bone marrow failure with leukopenia. Serious aplastic anemia must be excluded in these cases. A bone marrow examination, sometimes marrow biopsy, will provide the correct diagnosis.
Differentiation from myelodysplastic syndromes (MDS) is important. This disease group is heterogenous with a tendency for transition to acute leukemia in some cases. These patients often have bone marrow failure to some degree and generally do not benefit from intense chemotherapy since the effect on MDS is much poorer than on acute leukemia.
Differentiation between acute lymphatic leukemia and lymphoblastic lymphoma with bone marrow infiltration is difficult and may be somewhat artificial. There is evidence to support that the malignant cell population is of the same type, but that the disease primarily starts in lymph nodes or bone marrow.
Chronic myeloid leukemia can in some cases be confused with essential thrombocytosis. A finding of the Philadelphia chromosome and BCR-ABL will clarify this.
The Philadelphia chromosome-positive myeloid leukemia can morphologically resemble other myelo-proliferative diseases, for example, chronic myelomonocyte leukemia (CMML), and in rare cases, reactive granulocytosis from infectious diseases.
Chronic lympho-proliferative illness
Even when specimens of blood and bone marrow are successfully prepared, it is not always simple to achieve a definite diagnosis when bone marrow and/or blood is dominated by homogeneous mononuclear cells with a relatively mature appearance. For both the prognosis and treatment, it is very important to differentiate the subgroups of chronic lympho-proliferative diseases.
Lasting clonal B cell lymphocytosis will, in more than 90% of cases, appear to be chronic lymphatic leukemia.
Non-Hodgkins lymphomas with leukemization and bone marrow infiltration are sometimes confused with chronic lymphatic leukemia. Immunophenotyping of the leukemic cells or a lymph node biopsy will provide diagnostic and prognostic clarification and influence the choice of treatment.