•The thick blood smear is a useful, rapid, and low cost technique for the diagnosis of disseminated histoplasmosis.•Thick blood smears by Field stain method allow a high concentration of leukocytes per field to be visualized. The case of a 40-year-old woman who was admitted to the emergency room in cardiopulmonary arrest is reported. The patient's relatives reported an illness that had developed over the course of several weeks, consisting of general malaise, a dry and non-productive cough, fever, and progressive dyspnea at rest. Upon admission, cardiopulmonary resuscitation was performed for 10 min, with subsequent return of spontaneous circulation. A diagnosis of HIV was confirmed by serology, and laboratory tests revealed leukocytosis with neutrophilia, anemia, a low platelet count, prolonged clotting time, azotemia, and metabolic acidosis. Multilobar lung infiltrates with a cottony aspect and bilateral lung nodules were observed on chest X-ray (Figure 1A). Intra- and extracellular ovoid structures with a nucleus and without kinetoplast were observed in thick and thin blood smears stained with the Field stain method. These findings suggested Histoplasma capsulatum (Figure 1B, C). The patient died within 24 h of admission. The Histoplasma urinary antigen test is the method of choice for the diagnosis of disseminated histoplasmosis (Azar and Hage, 2017Azar M.M. Hage C.A. Laboratory diagnostics for histoplasmosis.J Clin Microbiol. 2017; 55: 1612-1620Crossref PubMed Scopus (118) Google Scholar). However, this test is not always available in developing countries. Although the peripheral blood smear has been described previously as an alternative diagnostic method, it is rarely performed (Dieng et al., 2017Dieng T. Massaly A. Sow D. Vellaissamy S. Sylla K. Tine R.C. et al.Amplification of blood smear DNA to confirm disseminated histoplasmosis.Infection. 2017; https://doi.org/10.1007/s15010-017-0989-0Crossref PubMed Scopus (4) Google Scholar). The thick blood smear is a useful, rapid, and low cost technique for the early diagnosis of disseminated histoplasmosis in immunocompromised patients in low income populations living in endemic areas. During smear preparation, erythrocyte lysis allows a high concentration of leukocytes per field to be visualized (Centers for Disease Control and Prevention, 2017Centers for Disease Control and Prevention Laboratory diagnosis of malaria. Staining for malaria parasites.2017Google Scholar), increasing the probability of identifying intra- and extracellular yeasts. Ethics statement: Written informed consent was obtained from the patient's relatives for the publication of this case report. Conflict of interest: None of the authors reports a conflict of interest, and there were no funding sources. All of the authors have submitted the ICMJE form for the disclosure of potential conflicts of interest.