A 24-year-old man comes to the clinic due to 2 weeks of progressive generalized weakness. He has also had significant bruising on his trunk that developed spontaneously without trauma. The patient has no known medical conditions and takes no medications. Temperature is 37.1 C (98.8 F) , pulse is 120/min, and respirations are 20/min. Conjunctival pallor is present. Cardiac examination reveals mild sinus tachycardia with no murmurs. Skin examination shows truncal ecchymoses but is otherwise normal. Laboratory results reveal a hemoglobin of 6.8 g/dL and a normal creatinine. Bone marrow aspiration is grossly pale and histologically appears diluted due to high lipid content. Which of the following laboratory patterns is most likely present in this patient?

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11ec160b_396f_c40f_9249_05fc1e1b5ac3_MD0001_00 This patient with a low hemoglobin level has several symptoms of anemia, including generalized weakness, tachycardia, and conjunctival pallor. The presence of spontaneous bruising in the absence of trauma likely indicates thrombocytopenia. Bone marrow aspirate reveals an abundance of lipids instead of cells, which is usually seen with bone marrow aplasia or hypoplasia. This constellation of findings is highly suggestive of aplastic anemia (AA). AA is a form of bone marrow failure primarily caused by cytotoxic T-cell destruction of multipotent hematologic stem cells. Because multipotent stem cells produce all mature blood cells, patients usually develop pancytopenia (not just anemia as the name suggests) and have manifestations of anemia, thrombocytopenia, and/or leukopenia (eg, infections). As with most forms of anemia, anemia-induced tissue hypoxia stimulates interstitial cells in the kidney to increase the release of erythropoietin. However, in AA, erythropoietin is unable to stimulate significant new red blood cell production due to the reduced population of functioning hematologic stem cells; therefore, reticulocytes are inappropriately low. Because the blood cells produced by the remaining undamaged hematopoietic stem cells are normal in morphology, erythrocytes are normal in size and appearance; therefore, mean corpuscular volume is normal. Because there is no intravascular hemolysis, haptoglobin (binds free hemoglobin in the blood) is also normal. Educational objective: Aplastic anemia (AA) is a form of bone marrow failure associated with pancytopenia and bone marrow aplasia/hypoplasia. Although erythropoietin levels are high, reticulocytes remain low because the production of new erythrocytes is impaired by a paucity of bone marrow stem cells. However, the blood cells produced by the remaining stem cells are normal in morphology and red cell indexes (eg, mean corpuscular volume) are usually normal.

A 24-Year-Old Man Comes to the Clinic Due to 2