Pulmonary Langerhans Cell Histiocytosis
A predominantly cystic lung disease is seen with temporal heterogeneity. Multiple lung nodules are seen in varying stages, with cavitated nodules, thick and thin walled cysts seen in different parts of the lungs. The nodules are peribronchiolar with irregular borders. The cysts are also irregular and show bilobed, cloverleaf and bizzare shapes. The coronal and sagittal reformatted images shows upper lobe predominance and sparing of costophrenic angles. These features are fairly pathognomonic of pulmonary Langerhans cell histiocytosis (PLCH). PLCH occurs almost exclusively in smokers (> 90%), and this patient was a chronic smoker. A biopsy confirmed the diagnosis. Smoking cessation led to significant improvement on follow-up.
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The other cystic lung disease, lymphangioleiomyomatosis (LAM) typically occurs in women of child bearing age, however the heterogeneity of the nodules, upper lobe predominance and sparing of the costophrenic angles rules out LAM, which may have apical sparing.
Septic emboli can have similar appearance however they show lower zone predominance with a septic focus in the body.
Birt Hogg Dube syndrome is a rare autosomal dominant disorder that can present as cystic lung disease and is characterized by skin lesions (fibrofolliculomas) with associated renal neoplasms and colonic polyposis. The cysts are thin walled and have basal, subpleural distribution.
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