Radiology

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Lymphocytic Interstitial Pneumonia (LIP) is a rare benign lymphoproliferative disorder of the lung that is categorized under interstitial lung diseases (ILDs) and is often associated with autoimmune diseases or immunodeficiency states.

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Etiology

Syndromic associations:

LIP is considered part of the spectrum of benign pulmonary lymphoid disorders, frequently associated with:

• Sjögren syndrome (most common)
• HIV infection (especially in children)
• Autoimmune thyroiditis
• Rheumatoid arthritis
• Systemic lupus erythematosus (SLE)
• Hypogammaglobulinemia
• Epstein-Barr virus (EBV) (in HIV-positive children)

2. Pathophysiology

• Characterized by diffuse polyclonal infiltration of mature lymphocytes, plasma cells, and histocytes within the alveolar septa, perivascular, and peribronchial interstitium.
• Considered reactive, not neoplastic, but may progress to lymphoma (especially MALT lymphoma) in a minority (~5%).

Clinical Features