Introduction: Over the years, hot tubs have gained a notorious infectious reputation from hot tub folliculitis due to pseudomonas infection to legionella pneumonia. A less discussed, but still prominent risk from hot tub usage is hypersensitivity pneumonitis due to mycobacterium avium complex exposure. This reputation, however, has not completely deterred those form using of hot tubs as described in the case below.

Case Presentation: 41 year-old female with PMH of ulcerative colitis presented complaining of dyspnea, fever, and malaise. One week prior, she went on a fishing trip followed by progressive malaise and fever, home recorded Tmax of 104.7 F. The day prior to presentation, she began to experience dyspnea worsened by exertion and lying flat with non productive cough, unchanged form baseline. She stated to have been in an dirty, enclosed hot tub for a few hours during her trip with others becoming ill as well. She does own cats, dogs, and horses. Denied recent exposure to tobacco, quit one year ago. Denied vaping as well. Ulcerative colitis was reportedly well controlled with only non-bloody diarrhea for a few days prior. On Imuran and Infliximab.

Physical Exam:
Vitals: HR 109, RR 27, BP 114/72, O2 sat 88%, and Temp 101.8F.
General Appearance: well-developed, not acute distress
HENT: Wearing HFNC Pulmonary: Clear to auscultation bilaterally, no wheezes or crackles
Cardiac: Heart regular rate and rhythm
Abdomen: Non-distended
Extremities: no clubbing, cyanosis, or edema
Neuro: Alert, no focal deficits.

Differential: Infection, inflammation in the setting of UC, lupus pneumonitis, pulmonary edema, hypersensitivity pneumonitis, COVID pneumonia, or pulmonary embolism.

BMP: Na 136, K 3.3, Cl 102, Bicarb 22, Anion Gap 12, GFR >60, BUN 8, Cr 0.91, Glucose 94, Calcium 7.6
CBC: WBC 3.3, Hg 10.3, MCV 104.2, Platelets 167
ABG: pH 7.39, pCO2 27.8, pO2 70,
Bicarb 16.6
ProBNP: 762 pg/mL
Lactic Acid: 1.9 mg/dL
Procalcitonin: 2.40 ng/mL
ANA prior to admission: 1:320
Legionella urine antigen: Positive

Hot tub water sampling: Positive for Mycobacterium Avium

Complex Chest Xray: Bilateral interstitial lung opacities which could be due to pulmonary edema or atypical/viral infection.

CT PE: No evidence of acute PE. Diffuse bilateral interstitial thickening and groundless and consolidate opacities with trace bilateral pleural effusions, favored infectious or inflammatory in nature. Severe pulmonary edema could have a similar appearance. Multiple prominent mediastinal hilarious lymph nodes, likely reactive.

Final/Working Diagnosis: Hypersensitivity pneumonitis due to Mycobacterium avium complex exposure from hot tub water.

Management/ Outcome/and or Follow-up: Placed on HFNC for oxygen supplementation. Initiated on Solu-medrol 60 mg BID with ceftriaxone and azithromycin for CAP coverage. Pulmonology consulted inpatient. Azathioprine held in the setting of concern for infection. Transitioned to oral prednisone 40 mg PO daily followed by 10 mg wean every 7 days followed by 5 milligrams for one additional week. Antibiotics switched to levoquin for 7 days in the setting of positive legionella antigen. At time of discharge, titrated down to and discharge on 3L NC with symptoms greatly improved.

Outpatient follow up with pulmonology two months after discharge. Repeat CXR noted few interstitial infiltrates, but vastly improved form prior. No longer requiring oxygen supplementation. Planned follow up CXR two weeks following visit, patient has yet to obtain.

References and Resources:

1. “ Hypersensitivity Pneumonitis Associated With Mycobacterium Avium Complex and Hot Tub Use.” Define_me, https://www.mayoclinicproceedings.org/article/S0025-6196(11)61814-4/pdf.
2. “Mycobacterium Avium Complex Infections.” Genetic and Rare Diseases Information Center, U.S. Department of Health and Human Services, https://rarediseases.info.nih.gov/diseases/7123/mycobacterium-avium-complex-infections.
3. American College of Physicians. MKSAP : Medical Knowledge Self-Assessment Program VIII. Philadelphia, PA :American College of Physicians, 19881989.