| Clinical | - Typical age range 20 to 40 years
- Nearly all affected individuals are current or former cigarette smokers*
- May be asymptomatic, with abnormal chest radiograph, or may report dyspnea, constitutional symptoms
- History of pneumothorax
- Diabetes insipidus (<10%)
- Bone lesions (<15%)
|
| Lung function tests | - Normal or reduced lung volumes and reduced diffusing capacity
- Airflow limitation and hyperinflation less common, typically in patients with more advanced, cystic disease
|
| HRCT | - Mix of nodules (2 to 10 mm) and thick-walled cysts (early stages) or bizarrely shaped cysts varying in size and shape (advanced stages)
- Upper and mid-lung zone distribution with sparing of costophrenic angles
- Can show scattered cystic lesions without nodules
- Can show peribronchial nodules without cysts
|
| Bronchoalveolar lavage | - BAL with ≥5% CD1a-positive cells is considered diagnostic, but frequently a lower percentage of CD1a cells is noted
|
| Histopathology | - Peribronchial inflammatory lesions containing an admixture of Langerhans cells, eosinophils, lymphocytes, and neutrophils
- Langerhans-like cells express CD1a, langerin (CD207), and S100
|
| Diagnosis based on clinical features and HRCT | - Classic HRCT features
- BAL with <5% CD1a-positive cells, but without lymphocytosis
- Improvement with smoking cessation
|
| Diagnosis based on BAL or biopsy | - Compatible clinical features and one of the following:
- BAL with ≥5% CD1a-positive cells
- Transbronchial or surgical lung biopsy demonstrating diagnostic histological features
- Compatible HRCT and extrapulmonary Langerhans cell histiocytosis confirmed by bone or skin biopsy
|
