What is pulmonary Langerhans cell histiocytosis?
Pulmonary Langerhans cell histiocytosis (PLCH) is a rare lung disease in which a type of immune cell, the Langerhans cell, collects around the small airways and forms nodules. Over time these nodules can hollow out into cavities and then thin-walled cysts, which damage the lung and reduce its capacity to transfer oxygen.
PLCH occurs almost exclusively in people who smoke, usually young adults between their twenties and forties. It is one of the smoking-related forms of interstitial lung disease. Langerhans cell histiocytosis is now classed as a myeloid neoplasm, and many lesions carry mutations in the MAPK signalling pathway, such as BRAF V600E. In adults with lung-only disease, however, it usually behaves as an inflammatory condition driven by smoking.
Most adults have disease confined to the lungs, but some have involvement of bone, the pituitary gland, skin or other organs. When this is suspected, care is coordinated with haematology and endocrinology.
Symptoms of PLCH
Around a quarter of patients have no symptoms, and the condition is found on a chest X-ray or CT. When symptoms are present, they include:
- Dry cough: often attributed to smoking for a long time.
- Breathlessness on exertion: slowly progressive.
- Sudden chest pain and breathlessness: caused by a collapsed lung (pneumothorax) when a cyst ruptures. This may be the first sign of the disease.
- General symptoms: tiredness, weight loss or fever.
- Excessive thirst and urination: a sign of diabetes insipidus from pituitary involvement.
- Bone pain from bone lesions in multisystem disease.
Causes and risk factors
Cigarette smoking is the dominant risk factor, and the vast majority of adults with PLCH are current smokers. Smoke is thought to stimulate the airway lining to attract and activate Langerhans cells. Cannabis smoking has also been implicated, and exposure to other inhaled smoke such as beedi may contribute.
The disease affects men and women. It is not inherited and is not contagious. Why only a small fraction of smokers develop PLCH is not fully understood, although acquired gene mutations in the abnormal cells play a part.
How PLCH is diagnosed
In a smoker with a typical CT appearance, the diagnosis can often be made with reasonable confidence. Biopsy is used when the picture is uncertain.
| Test | What it shows |
|---|---|
| High-resolution CT chest | Small nodules and bizarre-shaped cysts in the upper and middle zones, sparing the lung bases |
| Lung function tests | Reduced gas transfer, sometimes with airflow obstruction or restriction |
| Bronchoscopy with lavage | An increased proportion of Langerhans (CD1a-positive) cells, and exclusion of infection |
| Lung biopsy | Confirms the diagnosis when imaging is not typical |
| Echocardiogram | Screens for pulmonary hypertension, which can complicate PLCH |
| Bone scan, pituitary tests or PET-CT | Looks for disease outside the lungs when symptoms suggest it |
The cysts of PLCH can resemble those of lymphangioleiomyomatosis or Birt-Hogg-Dube syndrome. In India, cavitating nodules are sometimes mistaken for tuberculosis, so sputum testing for TB is often done in parallel.
Treatment of PLCH
Stopping smoking
Complete smoking cessation is the single most important treatment. In many patients it alone leads to stabilisation, and nodules may regress. This includes cigarettes, beedi, cannabis and, ideally, avoidance of vaping. Nicotine replacement, varenicline and behavioural support are offered.
Medicines
For progressive disease despite stopping smoking, or for multisystem disease, treatment is planned with haematology. Options include the chemotherapy agent cladribine or cytarabine. Where a BRAF or other MAPK pathway mutation is found, targeted therapies may be considered in selected cases. Corticosteroids are of uncertain benefit and are not routinely used.
Managing complications
Pneumothorax is treated with chest drain insertion and, because recurrence is common, a procedure to prevent recurrence (pleurodesis or surgery) is often advised. Pulmonary hypertension needs specific assessment. For advanced lung disease, referral to a transplant centre is considered.
Outlook and follow-up
The outlook in PLCH is variable but often favourable when smoking stops. Some patients improve, many stabilise, and a minority progress to extensive cystic disease, fibrosis or pulmonary hypertension. Follow-up involves lung function testing, CT scans when indicated, and echocardiography if breathlessness worsens out of proportion to the lung findings. Patients with PLCH have a higher risk of lung cancer and other smoking-related illness, which is another reason to stop smoking completely.
When to seek urgent care
Go to an emergency department straight away for sudden sharp chest pain with breathlessness, which may indicate a collapsed lung. Also seek urgent care for breathlessness at rest, coughing up blood, fainting or blue lips. Patients with known cystic lung disease should seek advice before air travel or diving.
Frequently asked questions
Will stopping smoking cure PLCH?
Stopping smoking is the most effective treatment and leads to stabilisation or improvement in many patients. Cysts that have already formed do not disappear, but further damage can often be prevented.
Is PLCH a cancer?
Langerhans cell histiocytosis is classified as a myeloid neoplasm because the abnormal cells carry acquired gene mutations. In adults with lung-only disease, however, it usually behaves as a smoking-related inflammatory condition and many patients never need chemotherapy.
Can I use e-cigarettes instead of cigarettes?
It is safest to avoid all inhaled smoke and vapour. Nicotine patches or gum and prescribed stop-smoking medicines are preferred as aids to quitting.
Why did my lung collapse?
Cysts near the surface of the lung can rupture and let air leak into the chest, causing a pneumothorax. Because this can recur, a procedure to seal the lung lining is often recommended after the first episode.
Can I fly with PLCH?
Most people with stable PLCH can fly. Air travel should be avoided for a period after a pneumothorax until it has fully healed and been confirmed on imaging. Discuss travel plans at your clinic visit.
Was my PLCH mistaken for tuberculosis?
This can happen, because cavitating nodules on a scan can resemble TB. A careful review of the CT pattern, smoking history and test results helps separate the two.
Related conditions and procedures
Consult Dr. Gogineni Ratnakara Rao
Apollo Hospitals, Financial District: Monday to Saturday, 8:30 AM to 5:00 PM. Anything in Lung Clinic, Chanda Nagar: Monday to Saturday (Thursday closed), 6:00 PM to 9:00 PM.