In this patient with longstanding Crohn's disease who was treated with immunosuppressants including anti-tumour necrosis factor (TNF), the finding of diffusely scatted pulmonary micronodules posed a diagnostic dilemma. The list of differential diagnoses included milliary TB, fungal infections, atypical infections, sarcoidosis, metastatic disease, hypersensitivity pneumonitis, early pulmonary histiocytosis and pulmonary Crohn's disease. Ruling out infectious and some non-infectious causes helped in establishing the correct diagnosis of concomitant pulmonary sarcoidosis.
TB and atypical infections in this case could be excluded by absence of caseating granuloma and negative cultures from bronchoalveolar fluid and lung biopsy specimens. Bronchiolar granulomas associated with alveolitis may be seen in patients with hypersensitivity pneumonitis as well.2
Although our patient had domestic exposure to duck feather and black moulds, negative serological studies along with the absence of any significant temporal association of symptom onset with exposure discounted the possibility of hypersensitivity pneumonitis. Pulmonary granulomas have been reported after the use of anti-TNF (infliximab) in patients with seropositive rheumatoid arthritis, but those granulomas were caseating.3
Diffuse non-caseating granulomatous inflammatory changes were seen on lung biopsy in this case. Granulomatous interstitial lung disease has been reported in Crohn's disease.4–6
Bronchial involvement has also been reported in two cases, one showing non-caseating granuloma, and epithelioid-like cells on bronchial biopsy in the other.7
In all, 53 cases of IBD and concomitant sarcoidosis have been reported in the literature.8 9
In some case the presence of mediastinal lymphadenopathy suggested true sarcoidosis. It seems almost impossible to determine histologically whether bronchopulmonary granulomatosis seen in patients with Crohn's disease should be considered sarcoidosis or an extraintestinal manifestation of Crohn's disease. Crohn's disease and sarcoidosis have no known aetiology, though they share the same pathological and immunological features and are characterised by non-caseating epithelioid granulomas and accumulation of CD4 T lymphocytes at the site of disease activity. Besides histology, raised serum calcium and angiotensin-converting enzyme (ACE) levels, no response to the purified protein derivative (PPD) test and presence of mediastinal lymphadenopathy were helpful in establishing the diagnosis of pulmonary sarcoidosis.
- Both inflammatory bowel disease (IBD) and sarcoidosis can cause granulomatous lung disease.
- IBD and sarcoidosis may exist concomitantly in some patients.
- Micronodules on chest radiograph has a wide differential possibility.
- A histological diagnosis should always be attempted.