Hemophagocytosis and Histoplasma‐like fungal infection in 32 cats

Abstract

Histoplasmosis is one of the most common systemic fungal diseases in cats from the United States. It commonly causes respiratory or disseminated disease and is often associated with one or more cytopenias. Here, we describe 32 cats in which a Histoplasma‐like fungal infection was associated with concurrent hemophagia in at least one sample site, commonly spleen, bone marrow, liver, and/or lymph node. The degree of hemophagia was characterized as moderate or marked in the majority of cases, and in all cases, there was a predominance of phagocytized mature erythrocytes. A few cases also had macrophages with phagocytized erythroid precursors, platelets, and/or neutrophils. Complete blood count results were available for 25 cats, and cytopenias were common (20/25), including solitary anemia (10), anemia and thrombocytopenia (5), solitary neutropenia (2), pancytopenia (2), and anemia and neutropenia (1). Bone marrow samples were only available in a small subset of cases, preventing the further assessment of the causes of the cytopenias. Hemophagocytosis has been previously reported in cats with neoplastic diseases and a cat with calicivirus infection, and likely occurs with other conditions as well, such as hemorrhage or hemolysis. Results of this report suggest that systemic fungal disease is an additional differential to consider when there is hemophagia in a feline cytology sample.

Hemophagocytic syndrome in a cat with immune‐mediated hemolytic anemia

“…Interestingly, increased hemophagocytic macrophages in bone marrow were not observed in this cat. Hemophagocytic syndrome is rarely diagnosed in cats, with only three case reports and one retrospective study reported in the literature to date 6–9 . Hemophagocytosis was observed in the bone marrow examinations of three case reports and 9 of 10 cats with histoplasmosis 6–9 .…”

“…Hemophagocytic syndrome is rarely diagnosed in cats, with only three case reports and one retrospective study reported in the literature to date 6–9 . Hemophagocytosis was observed in the bone marrow examinations of three case reports and 9 of 10 cats with histoplasmosis 6–9 . In humans, bone marrow hemophagocytosis was observed in approximately half of the patients diagnosed with HLH, and the absolute numbers of hemophagocytosis were low 10 .…”

“…[6][7][8] In addition, a retrospective study of 32 cats with histoplasma-like fungal infection was reported. 9 In humans, lymphoma is a common etiology of secondary HLH. 1 Therefore, we performed a clonality test, and the result was negative.…”

Hemophagocytic syndrome in a cat with Mycoplasma haemofelis infection

“…Interestingly, several, but not all, reports of canine and feline patients with hemophagocytic syndrome also document non-regenerative anemia as well. [4][5][6] It is possible that phagocytosis of erythroid precursors contributed to the nonregenerative nature of the anemia in this case, but it is possible other mechanisms were also involved. Given the lack of dysplastic changes in the erythroid lineage and no history of heavy metal exposure or heat stroke, the rubricytosis was most likely secondary to hypoxic bone marrow damage secondary to the marked anemia.…”

“…Several case reports in dogs have used similar criteria as in human cases, including bi-or pancytopenia and hemophagocytic macrophages in the bone marrow or spleen; the proportion of hemophagocytic macrophages required for diagnosis varied from >2% to >5%. [4][5][6][7] In this case, the presumptive diagnosis of hemophagocytic syndrome was based on bicytopenia and the presence of increased numbers of hemophagocytic macrophages in the spleen and bone marrow. Histiocytic sarcoma was ruled out based on the percentage of macrophages being <30% of the nucleated cells.…”