Disseminated Peritoneal Coccidioidomycosis Mimicking Malignancy in an Immunosuppressed Patient: A Case Report

Division

Far West

Hospital

Los Robles Hospital and Medical Center

Document Type

Case Report

Publication Date

12-12-2025

Keywords

disseminated coccidioidomycosis, peritoneal coccidioidomycosis, ustekinumab

Disciplines

Bacterial Infections and Mycoses | Immune System Diseases | Medicine and Health Sciences | Surgery

Abstract

Disseminated peritoneal coccidioidomycosis is rare and can mimic peritoneal carcinomatosis. Ustekinumab, an IL-12/23 inhibitor, impairs Th1/Th17 immunity which is critical for fungal control. No prior cases link ustekinumab use to disseminated fungal disease. We report a 45-year-old woman from an endemic region with prior pulmonary coccidioidomycosis and psoriatic arthritis on ustekinumab who presented with malignant-appearing ascites and omental caking. Fluid studies were non-diagnostic, but laparoscopic biopsies confirmed disseminated Coccidioides infection. She improved with liposomal amphotericin B followed by oral fluconazole suppression. This case highlights the need to consider peritoneal coccidioidomycosis in immunosuppressed patients, particularly on IL-12/23 blockade, and underscores the role of tissue diagnosis when fluid studies are negative.

Publisher or Conference

Journal of Surgical Case Reports

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