20th February 2025

Lymphoid interstitial pneumonia (LIP)

This is a rare IIP characterised by lymphocytic infiltration of the interstitium and alveolar spaces. There is often an underlying cause (such as CTD [connective tissue disease], immunodeficiency, infection or autoimmune disease), but it can also be idiopathic.

Dyspnoea and cough develop over years.

Investigations include:

• Blood tests: a polyclonal (or occasionally monoclonal) IgM gammopathy in serum immunoglobulins
• HRCT: predominantly ground-glass change, with mid-to-lower-lobe predominance
• BAL: often reveals lymphocytosis
• Histology: lymphocytic infiltration of alveolar septa

Steroids are the mainstay of management.