Pulmonary Langerhans Cell Histiocytosis

Single-system Pulmonary Langerhans cell histiocytosis (PLCH) is an uncommon type of Langerhans cell histiocytosis that affects only the lung. Langerhans cell histiocytosis (LCH) is blood disease which is now recognized as a cancer and can affect virtually any organ system of the body.

Single-system Pulmonary Langerhans cell histiocytosis (PLCH) is an uncommon type of Langerhans cell histiocytosis that affects only the lung. Langerhans cell histiocytosis (LCH) is blood disease which is now recognized as a cancer and can affect virtually any organ system of the body. Lung involvement in LCH can occur alone (single-system PLCH) or as multi-system disease (where it involves more than one organ system). PLCH is unique in that it has a strong association with smoking (over 95% cases) and many cases can resolve by quitting smoking. It is believed that cigarette smoke attracts specific immune cells in the lungs (Langerhans cells) which leads to a cascade of inflammation and injury to the air passages and lung tissue over time. PLCH causes the formation of multiple lung cysts (air-filled pockets inside the lung tissue), which can progress over time leading to loss of lung function.

The exact prevalence of single-system Pulmonary Langerhans cell histiocytosis (PLCH) is unknown. Current estimates suggest that there are between 25,000 – 50,000 patients with PLCH worldwide, however, these numbers are likely an underestimate.

The information on this page has been written and reviewed by the Histiocytosis Association Board of Trustees Scientific Committee and a member of the Histiocyte Society, and subsequently audited by patients and families to ensure enough information was captured. The most recent update to this page was in August of 2023.

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Is single-system PLCH a cancer?

Recently, cells from LCH tumors (lesions) were found to have cancer-causing DNA changes (mutations); these include mutations of the BRAF, MAP2K1, and ARAF genes. Previously thought to be an auto-immune disorder, LCH was classified as a blood cancer in 2008 by the World Health Organization. Recently, cancer-causing mutations in the BRAF- and other genes have also been found in cases with single-system PLCH, suggesting that a large proportion of these may be cancerous, driven by underlying inflammation from smoking.

What is the natural history and prognosis of single-system PLCH?

The natural history of PLCH is variable. In general, PLCH is a progressive disease and leads to a gradual decline in lung function over time. Smoking cessation can lead to complete reversal of single-system PLCH especially in the early stages (nodules). The inability to stop smoking is associated with a worse prognosis and can accelerate the loss of lung function leading to destruction of air passages and lung tissue in the form of cysts and fibrosis. Progressive PLCH can impair the oxygenation of lungs, resulting in increased pressure in the blood vessels of the lungs called as pulmonary hypertension. Single-system PLCH rarely spreads to other organs outside the lungs, but any new symptoms should prompt further investigations into additional sites of disease.


PLCH affects patients in different ways. The most frequently reported symptoms include shortness of breath, dry cough, sinus congestion in the early stages, and low oxygen levels in the blood in the advanced stages. Some individuals with single-system PLCH may have little to no symptoms at all.

Rarely, PLCH can cause collapse of the lung called as pneumothorax, which often requires an urgent procedure to expand the lung by using tubes or needle. The common symptoms of a pneumothorax include sudden onset chest pain and shortness of breath, typically more on one side.

About 10-15% of adults with PLCH will also have symptoms due to disease in organs outside of the chest, for example bone pain or skin rash.

Diagnosis and Treatment

Diagnosis of single-system PLCH:

The most important diagnostic test in patients with suspected single-system PLCH is a CT scan of the chest (CAT scan). In many patients, the CT scan may show changes that are highly suggestive of PLCH (the presence of cysts and/or nodules), and mostly in the upper and middle parts of the lungs. In many cases, there is a need to obtain a lung biopsy so it can be reviewed under the microscope to confirm the diagnosis and also allow for testing of BRAF and other cancer-causing mutations. Other tests (blood work, ultrasound of the abdomen, PET scan, MRI brain) may be indicated in some patients to understand the extent of disease and whether there is LCH affecting organs other than the lung. Tests to assess the function of the lung (pulmonary function tests) or effects on the heart (echocardiogram) are usually conducted.

What is the treatment for single-system PLCH?

Stopping smoking in any form (including marijuana, vaping, and eliminating second-hand smoke exposure) is key to the management of PLCH. Treatment options for individuals whose PLCH does not improve after successful smoking cessation include consideration of certain chemotherapy medications or targeted therapies. It is therefore important for the lung doctors (pulmonologists) to collaborate with cancer doctors (hematologists/oncologists) to treat such cases. Other medical therapies that may be used for advanced-stage PLCH include therapies for pulmonary hypertension and oxygen for selected patients.

Since cigarette smoking is also a common cause of other serious conditions (heart attack, emphysema or chronic obstructive pulmonary disease [COPD], lung cancer), it is critical to manage these conditions in individuals with PLCH to improve survival. Many individuals with single-system PLCH struggle with symptoms of chronic pain, fatigue, anxiety, and depression, which should be managed adequately alongside.

Other medical therapies that may be used to treat PLCH include therapies for pulmonary hypertension (a condition associated with elevated pressures in the lung circulation) and oxygen for selected patients. Because of the high risk of recurrence, patients with PLCH who develop a pneumothorax should undergo procedures such as pleurodesis (remove of excess fluid from the area between the lungs and chest wall) in order to prevent/reduce the risk of future pneumothoraxes.

The care of patients with PLCH is often provided by pulmonologists, although sometimes a multi-disciplinary approach with input from other specialists like a hematologist/oncologist or dermatologist may be necessary, depending on which organs are involved.

To learn more about Langerhans cell histiocytosis (LCH), including more information on treatment options to multisystem Pulmonary Langerhans cell histiocytosis (PLCH), click here. You can also give us a call at +1-856-589-6606 or email us at info@histio.org.


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