Pulmonary Langerhans cell histiocytosis

Pulmonary LCH

  • Unlike systemic Langerhans cell histiocytosis or that confined to bone (eosinophilic granuloma) which is seen in paediatric population, pulmonary LCH is usually identified in young adults (20-40 years of age).
  • Almost always there is a history of smoking.
  • There is proliferation of Langerhans cells in the bronchiolar and bronchial epithelium, forming granulomas –> these cellular granulomas evolve, peripheral fibrosis forms resulting in traction on the central bronchiole which becomes cyst-like –> explains the evolution from nodule to thick-walled cyst and finally to thin walled cyst.
    – Langerhans cells are  dendritic cells (antigen-presenting immune cells) of the skin and mucosa,
  • X ray is often non-specific, showing bilateral reticulonodular pattern with upper lobe predominance.
  • CT:
    –  Predilection for the mid and upper zones and regional sparing of the costophrenic recesses, anterior right middle lobe and lingula left upper lobe.
    – Nodules are often centrilobular
    – With time they cavitate & become cysts. The thin walled cysts can coalesce and become irregularly shaped.
  • Treatment: the only effective method is STOP SMOKING !! It is reversible by smoking cessation.
  • Complication: pneumothorax (from cysts rupture)

Clinical pearl:

  • Irregular cysts and nodules (which may cavitate) with upper lung predominance in a smoker should raise suspicion for the diagnosis

Reference: radiopaedia.org, auntminnie.com

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