Clinical observation of interstitial lung injury caused by the use of humidifier

Humidifier lung syndrome is a rare phenotype of hypersensitive pneumonitis (HP) caused by inhalation of fumes from contaminated climate appliances such as a humidifier and air conditioner. Since the described syndrome is rarely found in the Russian Federation, the practitioner should be wary of this pathology, carefully collect an anamnesis from the patient, and also carry out differential diagnostics with lung lesions of autoimmune, drug, infectious genesis. HP therapy includes exclusion of contact with the etiological factor and the appointment of systemic hormonal therapy.

Antigen avoidance and outcome of nonfibrotic and fibrotic hypersensitivity pneumonitis

BackgroundHypersensitivity pneumonitis (HP) is classified into nonfibrotic and fibrotic phenotypes. Patients with nonfibrotic HP often experience recurrence and develop fibrosis, whereas those with fibrotic HP have a poor prognosis. Although antigen avoidance has long been the first line of treatment for HP, its impact on prognosis has been poorly reported.MethodsMedical records of 121 patients with HP diagnosed by new diagnostic criteria of ATS/JRS/ALAT guidelines and treated at our institution in Saitama, Japan, were retrospectively analysed. HP was classified into nonfibrotic and fibrotic phenotypes and 6 HP subtypes: summer-type, bird-related, home-related, and occupational HP, humidifier lung, and hot tub lung. Achievement of reduced exposure to inciting agents was divided into complete antigen avoidance (CAA) and incomplete antigen avoidance (IAA) by HP subtype.ResultsOf the 74 patients with nonfibrotic HP, 30 achieved CAA and experienced no recurrence or development of fibrosis. In the remaining 44 patients with IAA, 24 (54.5%) experienced recurrence and/or development of fibrosis. The all-cause 5-year mortality rate in the 47 patients with fibrotic HP was 47.8%. Negative prognostic factors of HP-related mortality in these patients were <50% lymphocytes in bronchoalveolar lavage (BAL) and honeycombing. Multivariate analysis showed a tendency for IAA to be related to poorer survival (hazard ratio: 3.452, 95% CI, 0.964-12.359, p=0.057).ConclusionsIn the patients with nonfibrotic HP, CAA resulted in no recurrence or development of fibrosis and longer survival. In the patients with fibrotic HP, <50% lymphocytes in BAL and honeycombing were negative prognostic factors for mortality.

A case of humidifier lung with a difficult differential diagnosis from COVID-19

ABSTRACT Acute respiratory illnesses that presented with diffuse ground-glass opacities (GGOs) on chest computed tomography (CT) scan suggest the diagnosis of coronavirus disease 2019 (COVID-19). However, many other diseases show similar CT findings, which often offer a difficult differential diagnosis. Here, we report a case of humidifier lung, a rare phenotype of hypersensitivity pneumonitis (HP), which mimicked COVID-19. A 71-year-old man was admitted because of dyspnea and diffuse GGOs found on chest CT scan. Although COVID-19 was initially suspected, his symptoms rapidly improved by the next day. A medical interview revealed that he had started using an ultrasonic humidifier 1 month ago. A high-resolution CT (HRCT) scan showed ill-defined centrilobular nodules and mosaic attenuation, which are typical of HP but atypical of COVID-19. The inhalation challenge test confirmed the diagnosis of humidifier lung. History-taking of humidifier use and a precise HRCT interpretation are helpful to differentiate it from COVID-19.

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis is an immune-mediated lung disease in which the repeated inhalation of certain antigens provokes a hypersensitivity response, with granulomatous inflammation in the distal bronchioles and alveoli of susceptible people. A diverse range of antigens including bacteria (Thermophilic actinomycetes), fungi (Trichosporon cutaneum), animal proteins (bird antigens), mycobacteria, and chemicals may cause the disease. The commonest forms are bird fancier’s lung, farmer’s lung, humidifier lung, and metal-working fluid pneumonitis. In some cases no antigen is identified. Acute disease is characterized by recurrent episodes of breathlessness, cough, fevers, malaise, and flu-like symptoms occurring 4–8 hours after antigen exposure. Fever and basal crackles are the main physical signs. Chronic disease is characterized by the insidious development of dyspnoea and persistent pneumonitis, sometimes progressing to lung fibrosis. Clinical features are similar to those of other varieties of pulmonary fibrosis, but clubbing is uncommon.