Infectious disease diagnosis from a peripheral blood smear

This is a case of a 29-year-old man who sought care because of dehydration, fever, weight loss, and diarrhea. A technologist observed yeast-like organ isms in the patient's granulocytes, monocytes, and plasma upon examination of the peripheral blood smear The microorganisms were later identified as H istoplasma capsulatum, Other laboratory findings characteristic of dissemin ated histoplasmosis included leukopenia, lymphocytopenia, monocytopenia, an d marked elevation of lactate dehydrogenase activity and serum ferritin con centration. The patient was also positive for HIV. The rapid identification of H capsulatum on the peripheral blood smear aided in the prompt initiati on of therapy and reduced hospital length of stay.