Pulmonary Langerhans Cell Histiocytosis

Pulmonary Langerhans cell histiocytosis (PLCH) is an uncommon lung disease which usually affects young to middle aged smokers or former smokers. 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.

While the precise cause of PLCH remains unknown, almost all adults with PLCH (about 95%) have either smoked cigarettes or have been exposed to substantial second-hand smoke. It is believed that cigarette smoke causes activation and accumulation of specific immune cells in the lungs (Langerhans cells) which leads to a cascade of inflammation and injury to the bronchial tubes and lung tissue over time. In addition to cigarette smoke, there may also be a subset of patients where PLCH is caused by genetic mutations. Recent research has shown that mutations of the BRAF gene have been linked to the development of PLCH. Other mutations have been identified. The occurrence of BRAF or other mutations suggests that at least a proportion of PLCH may be a low-grade cancer.

The natural history of PLCH is variable. Some patients have an excellent prognosis, while others progress at a rapid rate. In general, PLCH is a progressive disease and leads to a gradual decline in lung function over time. The inability to stop smoking is associated with a worse prognosis, and can accelerate the loss of lung function.

The exact prevalence of PLCH is unknown. Current estimates suggest that there are between 25,000 – 50,000 patients with PLCH worldwide. These numbers are likely an underestimate.

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Symptoms

PLCH affects patients in different ways. Some patients have little or no symptoms at all. The most frequently reported symptoms include shortness of breath on exertion, and cough. Some patients experience fatigue, weight loss and sometimes even a low grade fever.

Approximately 15% of patients with PLCH may experience a pneumothorax (lung collapse due to leakage of air around the lungs). The common symptoms of a pneumothorax are 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

The most important diagnostic test in patients with suspected 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). Some patients may need a lung biopsy or additional testing to confirm a definitive diagnosis. 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 the lung.

Stopping smoking (or eliminating second-hand smoke exposure) is key to the management of PLCH. Smoking cessation may lead to disease stabilization, and even regression, in patients with PLCH. Treatment options in patients who continue to progress after successful smoking cessation include consideration of certain chemotherapy medications and other specific therapies. 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 pneumothoraces.

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.

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What Do I Do Now?

A new diagnosis of a histiocytic disorder can bring feelings of being overwhelmed, bewildered, scared, angry, sad, disappointed, helpless, and sometimes even feelings of guilt.  It is a time filled with unknowns, change, and new people and situations.  Most parents feel ill-equipped to understand what is happening to their child and how to navigate through the illness to recovery.  There are, however, strategies and resources that can help you, your child, and other family members get through the uncertain times that lie ahead. One step at a time, you can gather information, create a support system, learn how to cope with stress, and become a strong advocate for your Histio Warrior as part of the medical team. The following tips and suggestions are provided to help guide you through this journey toward your Histio Warrior's good health.