Clinical Scorecard: Hot tub lung may mimic refractory pneumonitis

At a Glance

Key Highlights

• A 66-year-old woman with persistent presumed hypersensitivity pneumonitis reported daily indoor hot tub use after a detailed exposure history was obtained.
• High-resolution CT showed centrilobular ground-glass nodules and mosaic attenuation; biopsy showed airway-centered and airspace granulomas, with rare MAC organisms detected by staining.
• BAL culture was negative, and hot tub water and filter components were not cultured, so the source and presence of active MAC infection were not definitively confirmed.
• Symptoms improved after hot tub avoidance, tapering immunosuppression, and initiation of azithromycin, ethambutol, and rifabutin; imaging later showed complete resolution.
• The authors advise considering hot tub exposure when reassessing persistent or treatment-refractory interstitial lung disease.

Guideline-Based Recommendations

Diagnosis

• Obtain a detailed exposure history, including targeted questions about hot tub use, when evaluating persistent interstitial lung disease.
• Interpret clinical history, imaging, histopathology, and microbiology together; this case had rare MAC organisms on biopsy staining but negative BAL culture and no cultured hot tub samples.

Management

• Strict hot tub avoidance was advised in this case.
• The article states that exposure elimination may be sufficient in most reported cases behaving like nonfibrotic hypersensitivity pneumonitis.
• Corticosteroids may be considered for more severe or persistent symptoms.
• Antimycobacterial therapy is generally reserved for selected patients with evidence suggesting MAC infection on biopsy or BAL, or failure to improve despite exposure avoidance and corticosteroid treatment.

Monitoring & Follow-up

• The case was followed clinically and with serial imaging; complete radiologic resolution was reported approximately 24 months after presentation.
• The article reports pulmonary function testing and high-resolution CT findings as part of the patient's evaluation.

Risks

• Hot tub lung may be mistaken for hypersensitivity pneumonitis from another presumed antigen source.
• The article describes recurrent acute hypoxic respiratory failure and persistent imaging abnormalities during the patient's earlier course.
• Definitive evidence of active MAC infection was limited in this case because BAL culture was negative and hot tub water and filter components were not cultured.

Patient & Prescribing Data

The report describes one 66-year-old woman with progressive exertional dyspnea and persistent presumed nonfibrotic hypersensitivity pneumonitis after daily indoor hot tub use.

After hot tub avoidance and tapering prednisone and mycophenolate, azithromycin, ethambutol, and rifabutin were started. Symptoms markedly improved, and serial imaging showed complete resolution approximately 24 months after presentation. The case does not establish that antimycobacterial therapy is required for all patients.

Clinical Best Practices

• Reassess presumed antigen sources and disease mechanisms when interstitial lung disease persists despite treatment.
• Ask specifically about indoor hot tub exposure during evaluation of persistent or treatment-refractory interstitial lung disease.
• Consider the possibility of both hypersensitivity pneumonitis and MAC infection, while recognizing that the case's microbiologic evidence was not definitive.

Related Resources & Content

• Respirology Case Reports (case report; article title: Hot tub lung may mimic refractory pneumonitis)