Posaconazole followed by combination itraconazole and terbinafine for treatment of disseminated histoplasmosis in a cat

Abstract

Abstract OBJECTIVE This is the first reported use of posaconazole for the treatment of feline disseminated histoplasmosis. ANIMALS Approximately 1-year-old female spayed domestic longhair cat. CLINICAL PRESENTATION, PROGRESSION, AND PROCEDURES The cat presented to our institution with weight loss, lymphadenomegaly, hepatosplenomegaly, limb edema, abdominal fluid distension and ulcerated cutaneous nodules. The cat had been previously diagnosed with disseminated histoplasmosis at another institution approximately 6 months prior. Clinical signs had been refractory to treatment with fluconazole. Itraconazole had next been tried, and the cat’s weight continued to decline, lesions failed to regress, and the cat formed abdominal fluid distension and marked pelvic limb edema. TREATMENT AND OUTCOME The cat was prescribed posaconazole along with prednisolone. The cat’s demeanor, body weight, and lesions all markedly improved. Histoplasma antigen was undetectable in urine samples while the cat was receiving posaconazole. However, posaconazole blood levels paired with markedly elevated ALT suggested potential toxicity and the drug was discontinued. Upon cessation of posaconazole, the cat’s lesions returned with cytologic evidence of intralesional Histoplasma yeast. Itraconazole combine with terbinafine was prescribed. At last follow-up, the cat was clinically well, off all anti-fungal medication, and without detectable Histoplasma antigen in the urine. CLINICAL RELEVANCE Posaconazole therapy showed promise in this case. Had a safe and therapeutic dose been arrived at, we suspect that posaconazole would have cleared or maintained clinical remission of this cat’s disease. This is the first report using posaconazole and the first successful report using combination itraconazole and terbinafine for the treatment of feline disseminated histoplasmosis. Generic drugs were used throughout this case report; the drug manufacturers are unknown to the authors.