A 26-month-old boy is brought to the physician suffering from recurrent febrile episodes, nocturnal sweats, weakness and fatigue over the past 9-months. Examination shows pallor and splenic enlargement.
Ultrasonography confirms splenic enlargement. Peripheral blood smear shows normocytic, normochromic red blood cells and few nucleated red blood cells; white blood cells show a left shift with a significant number of
blasts and giant platelets as well as platelet aggregates. Bone marrow aspiration and biopsy shows white blood cell blasts positive for CD42 and CD61 along with myeloid markers CD13 and CD33 and negative for CD3, CD5, CD7, CD20, CD22, and human leukocyte antigen-DR. Laboratory studies show:
Serum
White Blood Cell Differential
Eosinophils 5% (normal 1-3%)
Neutrophils 31% (normal 54-62%)
Lymphocytes 62% (normal 25-33%)
Bands 1% (normal 3-5%)
Coagulation Timing
Prothrombin 16.3 sec (normal 10.2-13.8 sec)
Thromboplastin 30.0 sec (normal 25-40 sec)
Coagulation Levels
Fibrinogen normal
D-dimer 4.96 mg/mL (normal < 0.35 mg/mL)
Which of the following is the most likely diagnosis?
A. Acute myeloid leukemia
B. Aplastic anemia
C. Immune thrombocytopenic purpura
D. Epstein-Barr viral infection
E. Papovavirus infection
F. Thrombotic thrombocytopenic purpura
In this case report, acute myeloid leukemia is the most likely diagnosis given the blasts were positive for
CD42 and CD61 (megakaryocyte specific antigen) along with myeloid markers CD13 and CD33.
Therapy with all-trans retinoic acid (ATRA) was initiated and then followed 5-days later with cytarabine
and anthracycline based induction polychemotherapy. He died four months after diagnosis.
Case Report: Acute Myeloid Leukemia (FAB M7)
A. Acute myeloid leukemia is suspected when a peripheral blood smear shows circulating leukemic blasts
and is definitively diagnosed when the bone marrow shows white blood cells expressing at least one
platelet antigen (CD41, CD42b, and CD61). By definition, AML is proliferation of myeloid precursors
with a reduced capacity to differentiate into more mature cellular elements. As a result, there is an
accumulation of leukemic blasts or immature forms in the bone marrow, peripheral blood, and
occasionally in other tissues, with a variable reduction in the production of normal red blood cells,
platelets, and mature granulocytes. AML is the most common acute leukemia in adults (3 to 5 cases per
100,000). However, AML accounts for less than 10% of acute leukemias in children less than 10 years of
age.
B. Aplastic anemia is suspected when the serum laboratory tests show low counts of erythrocytes and
leukocytes and platelets (pancytopenia). To confirm the diagnosis, do a bone marrow biopsy and confirm
the cellularity is less than normal. Severe aplastic anemia is a bone marrow cellularity of less than 30%
of normal with at least two of the following: an absolute neutrophil count (ANC) of <500/mm
3
, a platelet
count of <20 × 10
3
/mm
3
, and a reticulocyte count of <60 × 10
3
/mm
3
.
C. Immune thrombocytopenia purpura (ITP) is a diagnosis of exclusion. A platelet count less than
100,000/mm
3 with an otherwise completely normal patient profile indicates ITP.
D. EBV has a tropism (a predilection for a particular place within an organism due to an external stimuli)
for the deep nuclei, neuroimaging can show characteristic multiple foci of T2-weighted or FLAIR
hyperintensity in the hemispheric cortex, brain stem, bilateral thalami, and basal ganglia. Disorders that
affect both basal ganglia include Leigh syndrome, mitochondrial encephalopathy, Wilson disease, and
glutaric aciduria type 2.
E. Most immunocompetent people with detectable specific human parvovirus B19 (pvB19) antibodies do
not recall ever having had any specific symptoms. Arthritis and arthralgia during acute pvB19 infection
are more commonly observed in adults rather than children. The symptoms typically subside in weeks,
although the arthropathy may persist for months in 20% of affected women.
F. Thrombotic thrombocytopenic purpura (TTP) is uncharacteristic in pregnancy, but is otherwise
characterized by inactive ADAMTS13 enzymes, ecchymoses, fever, paleness, tachycardia, severe
headache, confusion, a low platelet count, anemia, abnormal blood smear (Schizocytes; broken red blood
cells), elevated bilirubin, elevated urine creatinine, hematuria, proteinuria, and a negative coombs test