Lymphocytic interstitial pneumonia (LIP) is a syndrome secondary to autoimmune and other lymphoproliferative disorders.

Lymphocytic interstitial pneumonia applies to disorders associated with both monoclonal or polyclonal gammopathy.

Possible causes of lymphocytic interstitial pneumonia include the Epstein–Barr virus, auto-immune, and HIV.

Arterial blood gases may reveal signs of hypoxemia when tested in a lab.

Resolution may occur with the use of highly active anti-retroviral therapy used in patients with HIV, which suggests that the virus alone may cause immune cells to proliferate, or immunosuppression caused by HIV may lead to other viruses that induce the proliferation of immune cells, leading to LIP.