The diagnosis is usually suspected following a CT scan. Typical features on CT include solid and sub-solid nodules, ground glass change and reticulation. There may be features of multi-system involvement such as adenopathy and splenomegaly. The commonest abnormality on<unk>  function testing is a decrease in gas transfer. Both obstructive and restrictive patterns on spirometry have been reported. The differential diagnosis includes infection, other interstitial<unk><unk> s and malignant<unk>  including lymphoma. Exclusion of infection is therefore an important step in management, but confirmation of the diagnosis requires<unk>  biopsy. In people who have<unk><unk>  prior to a diagnosis of CVID, the differential diagnosis includes sarcoidosis. Sarcoid is also characterised by<unk>  involvement of the<unk>  and therefore patients being investigated for sarcoid should have serum immunoglobulins measured to exclude CVID.
Granulomatous–lymphocytic interstitial lung disease
Usual interstitial pneumonia
Combined pulmonary fibrosis and emphysema
Pulmonary hyalinizing granuloma
Acute eosinophilic pneumonia
Cryptogenic organizing pneumonia
Pulmonary alveolar microlithiasis
Desquamative interstitial pneumonia