The case reported, in this article is one of a somewhat extensive cutaneous disease, which occurred in a man, 33 years of age, who gave the following history: The disease first made its appearance, eleven and a half years ago, at the back of the left ear, as a pimple which soon became pustular. The process extended forward, very slowly and gradually encroached upon and covered almost the entire face, the central portion of which now presents an atrophic cicatricial condition. Another similar lesion occurred, one month after the primary invasion, on the back of the hand, which healed in about four years, after treatment with caustic. A third lesion appeared on the right side of the scrotum (six months after), which increased in size for a year and then healed spontaneously. A fourth inoculation appeared, on the anterior surface of the left thigh just above the internal condyle, and grew for a year, after which it gradually healed spontaneously. A fifth lesion appeared on the back of the neck and also healed spontaneously after growing for a year. The disease when first examined presented many of the features of a lupus vulgaris.

There were no enlarged lymphatic glands and the patient's health had always been good. The family and personal history revealed no syphilitic or tuberculous taint.

Sections from the cutaneous lesions showed the presence of what appeared to be budding blastomycetes. The sections also presented pathological features similar to those seen in the first case recorded by Gilchrist; in many sections almost typical tubercles were found.

The organisms in the tissue are chiefly spherical, unicellular bodies varying from 10–20 µ in diameter, and consist of a doubly contoured membrane, which encloses a fine granular protoplasm with sometimes a vacuole. Many budding forms in various stages were found; nonucleus could be demonstrated, neither were any mycelium or hyphæ present in the tissues. The parasites were almost always found outside of cells, comparatively few being enclosed in giant cells.

Pure cultures of the organism were obtained directly from the cutaneous lesions in two places from the pus squeezed out from between the papillomatous variety of the lesion. The organism grew on all ordinary media, and especially well on potato and beer-wort agar. The cultures showed both budding forms and a fairly profuse mycelium. Older cultures, carried through many generations, produced sometimes little or no mycelium. The organisms in the cultures were round, ovoid, doubly contoured, refractive bodies, varying in size from about 10 to 20µ in diameter. The mycelium was, on rare occasions, of two varieties, very fine and also coarse with sessile buds and conidia.

Dogs, a horse, a sheep and guinea-pigs were successfully inoculated, the most striking results being nodules, grossly simulating tumors, in the lungs. Microscopically these nodules were of a chronic inflammatory nature and contained numerous parasites identical in appearance with those in the patient. In the tissues of none of the animals successfully inoculated was any mycelium found. Since our organism did not ferment sugar and produced in cultures mycelium, it may either belong to the blastomycetes or to the oidia, but in conformity with prevailing nomenclature we regard it as a blastomyces.

We shall term the disease which has been produced by this organism Blastomycetic Dermatitis. We give the name Blastomyces dermatitidis to the parasite which we have isolated and described in this paper.

In closing we are of the opinion that it would be advisable to examine more carefully all tuberculous lesions of the skin, and especially those of tuberculosis verrucosa cutis, for the presence of blastomycetes. This can be readily and rapidly done by soaking the unstained sections in ordinary liquor potassse, when the organisms if present will stand out as doubly contoured refractive bodies.

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