Suberosis

Suberosis is hypersensitivity pneumonitis caused by inhaling mouldy cork dust. Penicillium glabrum (formerly Penicillium frequentans) and Chrysonilia sitophila are the main antigens.

Exposure. Cork stripping, storage, boiling, grinding and stopper manufacture, mainly in cork producing regions of southern Europe and North Africa.

Epidemiology. Disease has been described in a minority of cork workers. It is more frequent where cork is stored damp.

Forms. Acute, subacute and chronic. Chronic disease leads to fibrosis and, with bronchitis, obstruction.

Associated conditions. Occupational asthma and chronic bronchitis may also occur in cork workers.

Pathophysiology.

Mould colonises stored cork and releases spores into dust. Inhaled antigens cause a type III and type IV hypersensitivity reaction with granulomatous alveolitis and bronchiolitis.

Persistent exposure leads to fibrosis.

• Acute: fever, chills, cough and dyspnoea 4 to 8 hours after exposure.
• Subacute and chronic: progressive dyspnoea, cough, fatigue and weight loss.
• Basal crackles, and clubbing in fibrotic disease.

Red flags.

• Resting hypoxaemia or rapid deterioration.
• Progressive fibrosis despite avoidance.

• Exposure history including cork storage conditions and processing stage.
• HRCT: ground glass centrilobular nodules, mosaic attenuation with air trapping, fibrosis in chronic disease.
• Spirometry with gas transfer: restrictive or mixed, reduced DLCO.
• Serum IgG precipitins to Penicillium glabrum and Chrysonilia sitophila show exposure.
• Bronchoalveolar lavage lymphocytosis over 20 to 30%.
• Biopsy when atypical; exclude tuberculosis and fungal infection.

Differential diagnosis. Sarcoidosis, other hypersensitivity pneumonitis, organic dust toxic syndrome, occupational asthma, chronic bronchitis, idiopathic pulmonary fibrosis, infection.

• Avoid the antigen. Remove from cork processing, or control mould by dry storage, ventilation and enclosure; respirators as an adjunct.
• Prednisolone 0.5 mg/kg orally once daily in the morning, maximum 40 mg daily, for 4 weeks. If symptoms, spirometry, gas transfer and imaging improve, taper to the lowest effective dose over 8 to 12 weeks, then stop. If there is no improvement, taper over 2 weeks and reconsider the diagnosis. Monitor glucose, blood pressure, weight, mood and infection, with bone protection if therapy exceeds 3 months. Exclude active tuberculosis first. Caution in diabetes and peptic ulcer; no renal adjustment.
• Chronic fibrotic disease with progression: nintedanib 150 mg orally twice daily with food, long term. Maximum 300 mg daily; reduce to 100 mg twice daily for adverse effects or mild hepatic impairment. Monitor liver enzymes monthly for 3 months, then every 3 months; manage diarrhoea. Avoid in moderate or severe hepatic impairment and in pregnancy; avoid when eGFR is under 30.
• Long term oxygen when resting PaO2 is under 7.3 kPa, or 7.3 to 8 kPa with polycythaemia or cor pulmonale.
• Lung transplant assessment in advanced fibrosis.

Monitoring. Symptoms, spirometry and gas transfer at 4 to 6 weeks, then every 3 to 6 months; HRCT at 6 to 12 months.

Referral and escalation. Respiratory and occupational physician; workplace assessment; transplant assessment for advanced disease; notification and compensation where required.