Lymphoid interstitial pneumonia

Last revised by Liz Silverstone on 29 Apr 2024

Lymphoid interstitial pneumonia (LIP), also known as lymphocytic interstitial pneumonitis, is a benign lymphoproliferative disorder characterized by lymphocyte predominant infiltration of the lungs. It is classified as a subtype of interstitial lung disease. It also falls under the umbrella of non-lymphomatous pulmonary lymphoid disorders.

Lymphoid interstitial pneumonia can occur at any age. However, most of the patients are adults with a mean age of 52-56 years. If a child presents with lymphoid interstitial pneumonia, this can be indicative of AIDS.

There is a recognized female predilection (by ~2 fold) most likely attributable to the fact that lymphoid interstitial pneumonia occurs in patients with autoimmune diseases such as Sjögren syndrome, which is by far more common in women 8.

The main clinical symptoms are a gradual onset of dyspnea and cough with approximately 6 months duration. Less frequently, patients may have systemic symptoms such as fever, night sweats, arthralgia, and weight loss. If the disease progresses to end-stage respiratory failure, cyanosis and clubbing may develop. Hypertrophy of the salivary glands may be seen in 20% of patients 11

It is considered a benign lymphoproliferative disorder characterized histologically by diffuse interstitial and alveolar infiltration with polyclonal lymphocytes and plasma cells.

In about 80% of patients polyclonal or IgM monoclonal gammopathy is found 8.

Features can be non-specific, but may include:

The following features may be seen with lymphoid interstitial pneumonia on HRCT, but the findings are not exclusive to its diagnosis:

Scattered thin-walled perivascular cysts are commonly seen in Sjogren’s syndrome however these are most likely due to multifocal lung destruction by macrophage metalloproteinases rather than LIP. Macrophages are attracted to sites of protein deposition and the thin-walled cysts may contain internal strands, identical to those seen in light chain deposition disease and other lymphoplasmacystic disorders 16, 17.

The natural history is variable, from near-complete resolution to progressive disease. More than 30% of patients will develop end-stage disease and honeycombing despite treatment. According to some reports, 5-year mortality can range between 33-50% ref.

Transformation to lymphoma can occur, particularly in a patient with monoclonal gammopathy or hypogammaglobulinemia 8. Corticosteroids have been successfully trialled 1.

Approximately 5% of cases may transform into lymphoma 15.

It was originally classified as an idiopathic interstitial pneumonia in 1969 by Liebow and Carrington.

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