Clinical History
A 40-year-old female long term smoker presented with 3-4 months of non-productive cough and dyspnoea. She was otherwise well and did not have symptoms related to any other system. Initially she was evaluated with CT chest (showing findings below). There was a re-evaluation with follow-up CT after 8 months following cessation of smoking.
Imaging Findings
The initial chest CT images (figure 1a-g) show multiple small (5-10 mm) ill defined pulmonary nodules which have an overall predilection towards the upper and middle lobes. The costophrenic recess are spared. Some nodules appear solid while others show cavitation. This scan also shows diffuse airway thickening with scattered centrilobular emphysematous changes suggestive of a smoking related airway disease. The overall lung volumes were preserved. No mediastinlal lymphadenopathy. The subsequent follow up CT (figure 2a-g) after cessation of smoking shows dramatic interval response with resolution of most nodules and with no new or developing change.
Discussion
Pulmonary Langerhans cell histiocytosis (PLCH) is an idiopathic disorder characterised by an abnormal proliferation of Langerhans cells (a dendritic cell) in the lungs (1, 3-4). As seen in our patient, LCH in adults is usually a single system disease limited to the lungs. However, LCH may also be a multi system disorder in which essentially any part of the body can be affected. Multisystem LCH is more common in the paediatric population with peak incidence between 1-3 years of age.
In adults, the condition almost exclusively manifests in smokers.
Clinical perspective:
Patients usually present with a non productive cough and/or dyspnoea. Non specific constitutional symptoms may also be present while approximately 25% can be asymptomatic. Occasionally the presenting symptom can be a spontaneous pneumothorax.(5)
Imaging perspective:
Plain radiography in early changes can show a diffuse bilateral reticulonodular pattern with an upper and middle lobar predilection(4). During the course of the disease, small cysts can form within the nodular opacities. The lung volumes are typically preserved. Associated lung hyperinflation may be seen at times.
CT scans confirm small nodular lesions with a typical upper to mid zonal predilection with sparing of costophrenic recesses.(3-4) The nodules seen in the early stage of the disease are typically small (ranging around 1-10mm size) and are mostly centrilobular in distribution. The margins of the nodules are irregular. During the course of the disease, nodules may cavitate forming cystic spaces of variable wall thickness (1-2, 3-4). Bizarre shaped cysts may form during the later stage of the disease.
Outcome:
The typical imaging findings supported by long-term smoking history(2) were the clue to diagnosis. The excellent clinical and radiological improvement following cessation of smoking was further supportive of the diagnosis. Pertinent negative features such as absence of vasculitic markers such as ANCA as well as absence of clinical features of systemic sepsis, mediastinal lymphadenopathy helped to further narrow the differential diagnosis.
Teaching points:
This can highlight the typical imaging findings in the appropriate clinical context in being confident of diagnosis by imaging and therefore obviating need for invasive tissue diagnosis. The patient has had a good clinical response and has remained well to date following cessation of smoking.
Differential Diagnosis List
Pulmonary Langerhans cell histiocytosis
Pulmonary vasculitides (e.g. Wegeners granulomatosis)
Septic emboli
Sarcoidosis (nodular forms)
Final Diagnosis
Pulmonary Langerhans cell histiocytosis
