Definition: LIP is a form of 'idiopathic' interstitial pneumonia.

Synopsis

 dense and diffuse alveolar septal infiltrates associating lymphocytes, plasmocytes, plasmacytoid cells and macrophages
 +/- multinucleated giant cells
 +/- small ill-defined epithelioid granuloma
 +/- interstitial fibrosis
 +/- microscopic honeycomb remodeling
 +/- BALT hyperplasia (pulmonary lymphoid hyperplasia)

Associations

 pulmonary infections

• Pneumocystis jiroveci pneumonia
• Epstein-Barr virus infection
• HIV infection
• Legionella pneumonia
• tuberculosis
• Mycoplasma
• Chlamydia

 hypersensitivity pneumonitis (extrinsic allergic alveolitis)

 dysimmunity and auto-immunity (39%)

• Sjögren syndrome
• rheumatoid arthritis
• systemic lupus erythematosus
• Hashimoto thyroiditis
• myasthenia gravis
• pernicious anemia
• drug-associated lung injury
• toxin-associated lung injury
• bone marrow transplantation
• hypogammaglobulinemia
• celiac sprue
• primary biliary cirrhosis

 immunodeficiency diseases (14%)

• HIV infection +/- DILS
• genetic immunodeficiency syndromes
  • common variable immunodeficiency (CVID) (#10607809#)
  • agammaglobulinemia

 allogenic bone marrow transplantation (pulmonary GVHD)
 drug reactions
 pulmonary alveolar microlithiasis

Differential diagnosis

 NSIP
 low-grade lymproliferative disease
 hypersensitivity pneumonitis
 atypical mycobacterial infections
 pulmonary drug reactions

See also

 other pulmonary lymphoid hyperplasias

• BALT hyperplasia (follicular bronchiolitis)
• pulmonary nodular lymphoid hyperplasia

 lymphoid pneumonitis

• nonspecific interstitial pneumonitis (NSIP)

References

 Swigris JJ, Berry GJ, Raffin TA, Kuschner WG. Lymphoid interstitial pneumonia: a narrative review. Chest. 2002 Dec;122(6):2150-64. PMID: #12475860#