S2232 Gastrointestinal Histoplasmosis Masquerading as Crohn’s Disease in the Immunocompetent Adult

Abstract

INTRODUCTION: A misdiagnosis of gastrointestinal histoplasmosis (GIH) as Crohn’s disease can be catastrophic. Endoscopic data for GIH false negative biopsy rates are not well-established in the literature. CASE DESCRIPTION/METHODS: A 38-year-old female from Ecuador presented to the gastroenterology clinic with abdominal pain, weight loss, and chronic diarrhea. She denied pulmonary symptoms, fever or recent travel for several years. Her past medical and surgical history were significant for treated hepatitis C and C-section. Physical exam revealed a diffuse and mildly tender abdomen. Outpatient colonoscopic exam reported multiple ulcers. Biopsies at ulcer margins revealed non-necrotizing granulomas. Special tests were negative for CMV, TB and fungal organisms. HIV and C. difficile were ruled out. Presumed Crohn’s disease was diagnosed. Mesalamine 1 gm QID and Prednisone 60mg taper were started. At follow up, the patient was admitted to the hospital with worsening diarrhea, abdominal pain and fever. CT abdomen/pelvis showed diffuse enterocolitis. Vancomycin and meropenem were initiated and steroids discontinued. She developed hematochezia requiring multiple blood transfusions. A flexible sigmoidoscopy found severe inflammation extending from the rectum to the sigmoid (Figure 1). A total abdominal colectomy with ileostomy for fulminant and refractory disease was performed. GMS staining revealed a vast number of yeast consistent with histoplasmosis (Figure 2). Amphotericin B followed by itraconazole was started with serial antigen monitoring. The patient’s symptoms resolved and she was discharged with an extended itraconazole regimen. DISCUSSION: This case highlights the unique challenges in GIH. The organism may persist within granulomas for years. Reactivation of latent GIH has been described in the literature and would explain our patient’s disease course. Her initial symptoms could be explained by underlying Crohn’s disease or spontaneous progression of histoplasmosis. Perhaps the greatest challenge was the initial interpretation of the negative GMS stain leading to a significant diagnostic dilemma. Histology with GMS staining may help reveal the organism, and is considered a rapid and reliable diagnostic test. However, sensitivity data is not well established. Previous case series have demonstrated a false negative rate of 11% in an AIDS population. The sensitivity data in immunocompetent hosts is not known. Importantly, a misdiagnosis will lead to treatment error and a potential fatal outcome.Figure 1.: Severe colitis and large sigmoid ulcer with proximal stricture.Figure 2.: GMS stain after total colectomy showing ovoid yeast cells consistent with histoplasma organisms.