The Clinical Picture

Mediastinal granuloma due to histoplasmosis in a patient on infliximab

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A 50-year-old man with Crohn disease and psoriatic arthritis treated with infliximab and methotrexate presented to a tertiary care hospital with fever, cough, and chest discomfort. The symptoms had first appeared 2 weeks earlier, and he had gone to an urgent care center, where he was prescribed a 5-day course of azithromycin and a corticosteroid, but this had not relieved his symptoms.

Figure 1. (A) An enlarged lymph node (2.4 cm × 2.0 cm) at the bifurcation of the bronchus intermedius. (B) An enlarged inferior mediastinal lymph node (2.0 cm × 5.4 cm).

Figure 1. (A) An enlarged lymph node (2.4 cm × 2.0 cm) at the bifurcation of the bronchus intermedius. (B) An enlarged inferior mediastinal lymph node (2.0 cm × 5.4 cm).

He reported no recent travel, exposure to animals, or sick contacts. His temperature was 38.3°C (100.9°F). Results of the physical examination and initial laboratory testing were unremarkable. Chest computed tomography revealed prominent right hilar and mediastinal lymphadenopathy (Figure 1).

Bronchoscopy revealed edematous mucosa throughout, with minimal secretion. Specimens for bacterial, acid-fast bacillus, and fungal cultures were obtained from bronchoalveolar lavage. Endobronchial lymph node biopsy with ultrasonographic guidance revealed nonnecrotizing granuloma.

Bronchoalveolar lavage cultures showed no growth, but the patient’s serum histoplasma antigen was positive at 5.99 ng/dL (reference range: none detected), leading to the diagnosis of mediastinal granuloma due to histoplasmosis with possible dissemination. His immunosuppressant drugs were stopped, and oral itraconazole was started.

At a follow-up visit 2 months later, his serum antigen level had decreased to 0.68 ng/dL, and he had no symptoms whatsoever. At a visit 1 month after that, infliximab and methotrexate were restarted because of an exacerbation of Crohn disease. His oral itraconazole treatment was to be continued for at least 12 months, given the high suspicion for disseminated histoplasmosis while on immunosuppressant therapy.

DIFFERENTIAL DIAGNOSIS OF GRANULOMATOUS LUNG DISEASE AND LYMPHADENOPATHY

The differential diagnosis of granulomatous lung disease and lymphadenopathy is broad and includes noninfectious and infectious conditions.1

Noninfectious causes include lymphoma, sarcoidosis, inflammatory bowel disease, hypersensitivity pneumonia, side effects of drugs (eg, methotrexate, etanercept), rheumatoid nodules, vasculitis (eg, Churg-Strauss syndrome, granulomatosis with polyangiitis, primary amyloidosis, pneumoconiosis (eg, beryllium, cobalt), and Castleman disease.

There is concern that tumor necrosis factor antagonists may increase the risk of lymphoma, but a 2017 study found no evidence of this.2

Infectious conditions associated with granulomatous lung disease include tuberculosis, nontuberculous mycobacterial infection, fungal infection (eg, Cryptococcus, Coccidioides, Histoplasma, Blastomyces), brucellosis, tularemia (respiratory type B), parasitic infection (eg, Toxocara, Leishmania, Echinococcus, Schistosoma), and Whipple disease.

HISTOPLASMOSIS

Histoplasmosis, caused by infection with Histoplasma capsulatum, is the most prevalent endemic mycotic disease in the United States.3 The fungus is commonly found in the Ohio and Mississippi River valleys in the United States, and also in Central and South America and Asia.

Risk factors for histoplasmosis include living in or traveling to an endemic area, exposure to aerosolized soil that contains spores, and exposure to bats or birds and their droppings.4

Fewer than 5% of exposed individuals develop symptoms, which include fever, chills, headache, myalgia, anorexia, cough, and chest pain.5 Patients may experience symptoms shortly after exposure or may remain free of symptoms for years, with intermittent relapses of symptoms.6 Hilar or mediastinal lymphadenopathy is common in acute pulmonary histoplasmosis.7

The risk of disseminated histoplasmosis is greater in patients with reduced cell-mediated immunity, such as in human immunodeficiency virus infection, acquired immunodeficiency syndrome, solid-organ or bone marrow transplant, hematologic malignancies, immunosuppression (corticosteroids, disease-modifying antirheumatic drugs, and tumor necrosis factor antagonists), and congenital T-cell deficiencies.8

In a retrospective study, infliximab was the tumor necrosis factor antagonist most commonly associated with histoplasmosis.9 In a study of patients with rheumatoid arthritis, the disease-modifying drug most commonly associated was methotrexate.10

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