Draining skin lesion from a desert poodle

A 16-month-old intact female Poodle in Arizona had a history of intermittent coughing of a few weeks duration. Coccidiomycosis antibody screening test results were negative for immunoglobulin (Ig) M, but were positive (1:64) for IgG. Fine needle aspiration specimens of a draining lesion on the right palmar front foot contained large numbers of neutrophils, many of which contained bacteria, and lower numbers of macrophages. A few small structures also were observed, 2-5 microm in diameter with thin, nonstaining capsules and small, round to oval densely aggregated, eccentric nuclei. Cytologic findings were consistent with septic pyogranulomatous inflammation with Coccidiodes immitis endospores. Fungal culture of a sample from the draining lesion yielded white growth with barrel-shaped arthroconidia. Identification of the organism as C immitis was confirmed by a commercial DNA probe test. Although coccidioidomycosis often is diagnosed by microscopic identification of C immitis spherules in cytologic specimens, in this case only endospores, which are released from mature spherules, were observed. In cases of suspected coccidiodomycosis, the unique morphology of endospores may be useful in making a cytologic diagnosis.