Case Report

A Woman with Cough, Fever, and Micronodular Infiltrates on Chest Radiograph

Authors: Viranuj Sueblinvong, MD, Gilman B. Allen, MD

Abstract

Hot tub lung is a form of hypersensitivity pneumonitis (HP) reported to be associated with exposure to large aerosolized inocula of Mycobacterium avium complex (MAC). Although the pathogenesis of the disease is still poorly understood, the pathology of MAC-related HP can be similar to that of sarcoidosis, with well-formed granulomas. We describe a patient with HP featuring well-formed granulomas on transbronchial biopsy specimens, a finding believed to be unique to MAC-related HP, also referred to as “hot tub lung.”


Key Points


* In the case of Mycobacterium avium complex (MAC)-related hot tub hypersensitivity pneumonitis (HP), biopsy specimens often reveal well-formed bronchiolocentric granulomas, unlike the poorly formed granulomas classically described in HP from other sources.


* When a source of exposure can be identified, and the characteristic findings of HP are present on CT-imaging of the lung, disease caused by MAC in the immunocompetent host may represent a hypersensitivity-driven pneumonitis rather than infection. This is supported by the non-necrotizing granulomas seen on biopsy, and the improvement in symptoms following avoidance of further exposure.


* A predominance of CD8+ lymphocytes in bronchoalveolar lavage fluid is not uniformly observed in HP; a predominance of CD4+ lymphocytes can be seen in the early phase of HP.


* In cases where antigen-specific serum antibody assays are not possible, and tissue cultures are unrevealing, home environmental inspection and testing may yield important clues to the etiology of HP.

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