Fibrotic hypersensitivity pneumonitis after long-term exposure to household mold

History of present illness

A 58-year-old man presented to the outpatient clinic complaining of cough and shortness of breath during exercise. These symptoms had begun about 1 year earlier and had progressively worsened. Chest radiography, requested by the primary care physician, revealed a reticular interstitial pattern, diffusely involving both lungs ( Fig. 1.1 ). Consequently, he was referred to the pulmonology department.

Past medical history

The patient was a plumber and a former smoker of 20 cigarettes per day, with a 30-pack-year history of smoking. When asked about potentially harmful exposures, he said he lived in a damp, old house. He had never undergone pulmonary function testing. He took daily medications only for arterial hypertension.

Physical examination and early clinical findings

At the time of the visit to the pulmonologist, the patient was in fair general health condition, afebrile, and cooperative. Oxygen saturation measured by pulse oximetry (SpO ₂ ) was 95% on room air but rapidly decreased to 86% when he started to move. Similarly, he had shortness of breath and tachypnea when walking.

On chest examination, there were bilateral fine crackles, especially on pulmonary bases, and bronchiolar squeaks. There was also digital clubbing at the physical examination. He did not complain of joint stiffness or other signs or symptoms of a rheumatological disease.

Clinical course

During the visit, the patient underwent pulmonary function tests that showed a restrictive pattern and a significant reduction in the diffusing capacity of the lungs for carbon monoxide (DLCO) ( Fig. 1.2 ).

Autoimmunity tests (antinuclear antibody [ANA], anti-extractable nuclear antigens [ENA], anti-neutrophil cytoplasmic antibodies [ANCA], rheumatoid factor) were negative. A slight increase in nonspecific markers of inflammation was found erythrocyte sedimentation rate [ESR] 34.5 mm/hr (normal values for men aged 51–85 < 20 mm/hr) and C-reactive protein [CRP] 21.2 mg/L (normal values < 10 mg/L).

Searching for specific precipitin IgG was done, and a slight increase in IgG for pigeon droppings and Aspergillus fumigatus was found.

High-resolution computed tomography (HRCT) of the chest revealed bilateral reticular opacities with distortion of the pulmonary parenchyma, traction bronchiolectasis, honeycombing in the medium lung fields, and small areas of ground-glass opacities. Radiological changes in the lung parenchyma were relatively base-sparing but had no clear base-to-apex gradient ( Fig. 1.3 ).

BAL was done. Total cells were 200.000/mL with neutrophils 5%, macrophages 88%, and lymphocytes 5% of total cells.

Because neither chest HRCT scan nor BAL was conclusive in distinguishing idiopathic pulmonary fibrosis (IPF) from HP, after a multidisciplinary team meeting (MDD), the patient was offered a pulmonary biopsy in video-assisted thoracic surgery (VATS).

The histological examination on the lung biopsy showed fibrosis predominantly centrilobular and bridged between different lobule centers. Honeycombing and centrilobular microgranuloma were also reported ( Fig. 1.4 ).