Histoplasmosis—The Pathologic and Clinical Findings

¹ The Milwaukee County General Hospital and from the Department of Pathology and Bacteriology, Marquette University School of Medicine, Milwaukee, Wisconsin.

Histoplasmosis is generally a fatal systemic disease caused by the yeast-like fungus named Histoplasma capsulatum. This organism may be found within the reticulo-endothelial system. The infection is probably transmitted from animals, notably dogs.

The four principal clinical features of the disease are: 1) Gastro-intestinal manifestations of ulcerations and diarrhea. 2) Skin findings of chronic ulcerations and abscess formations. 3) Cardiac or joint manifestations. 4) Lymphadenopathy, hepatomegaly and splenomegaly. Lung findings are recorded in about twenty per cent of the cases. The findings are not characteristic and are frequently confused with tuberculosis. This is particularly true of pulmonary calcifications. The work of Palmer and Furcolow indicates that there is a high incidence of pulmonary calcifications in people with negative tuberculin tests. A number of such individuals, however, have a positive reaction to the intracutaneous injection of histoplasmin. This work was carried on among student nurses. The highest incidence reported was that in Kansas City, Missouri, where 58.1 per cent were positive skin reactors. It was also shown that there was a difference in the distribution of the positive tuberculin skin reactors and the positive histoplasmin reactors. The majority of the histoplasmin reactors are demonstrable between the ages of five and twenty years of age; whereas, the tuberculin reactors are found in the third and fourth decades. Both white and negro individuals have a higher incidence of histoplasmin positive reactors at the age of eighteen than tuberculin positive. It is likewise shown that in those who are histoplasmin negative and tuberculin positive the incidence of pulmonary calcification is about 17 per cent; however, those with histoplasmin positive and tuberculin negative skin tests have the highest incidence of pulmonary calcifications which is slightly greater than 90 per cent. Somewhat similar studies were also carried out by Aronson in reference to coccidiodin positive reactors and pulmonary calcification. It must be pointed out, however, that the individuals who react positively to this skin test do not have proven or clinical histoplasmosis. The reaction may be due to some immunologically similar infection. It is probably important to consider that quiescent pulmonary calcifications, if they are due to histoplasma capsulatum, may serve as the focus for the usual fatal systemic infection.

The cases of histoplasmosis usually have a gross picture similar to that of leukemia. Caseous necrosis of the adrenals is particularly common in these individuals. Histologically the organisms, averaging between 3 and 5 microns and surrounded by a capsule, may be seen throughout the reticulo-endothelial system contained in the phagocytic reticulum cells. From the laboratory standpoint a profound secondary anemia, leukopenia and thrombocytopenia are quite frequent.

There are two cases reported from the state of Wisconsin to date. Neighboring states also have cases: Illinois 4, Michigan 10, Minnesota 1, and Iowa 1.