Teaching Case

A five-year-old female child presented with fever, cough and difficulty in breathing since one week. On chest auscultation, vesicular breathing sounds were identified with no adventitious sounds and percussion was normal. General and physical examination did not reveal any other significant abnormality.

Chest X-ray showed diffuse reticular opacities in bilateral lungs predominantly in bilateral perihilar regions (Fig 1a). Patient received antibiotics for a week without resolution of clinical symptoms or radiographic findings. CECT thorax was performed which showed mosaic attenuation of bilateral lungs with areas of ground-glass opacities and hyperinflation. Also, tiny cystic lesions were seen diffusely distibuited in bilateral lungs with few large multilobated cysts showing bizarre configuration in the right perihilar region (Fig 1b,c).  The visualized section of upper abdomen showed dilatation of bilobar intrahepatic biliary radicals with wall thickening (Fig 1d). CBD was normally visualized with no obvious obstructive lesion.

On imaging, the provisional diagnosis of Langerhans cell histiocytosis (LCH) with associated primary cholangitis was considered. A differential consideration included lymphocytic interstitial pneumonia with infective (CMV) cholangitis. The patient was found negative for HIV. A skeletal radiographic survey was performed which revealed a well-defined lytic lesion in occipital bone (Fig 2). FNAC was performed which confirmed the diagnosis of LCH.

LCH is a multisystem dendritic cell disorder characterized by idiopathic infiltration and accumulation of abnormal histiocytes within various tissues and organs including bone marrow, skin, lung, liver, central nervous system, spleen and lymph nodes [1]. Pulmonary involvement is uncommon in children and is seen in young adults with a history of smoking. It can be diagnosed on CT thorax which usually shows cysts, nodules, ground-glass opacities, mosaic attenuation, septal thickening and areas of emphysema [2-4]. Presence of bizarre, bilobed or branching cysts present is highly suggestive of LCH as seen in our case [2-4]. The lungs adjacent to the nodules and cysts are usually spared in LCH, however, in the present case, it was involved suggesting advanced disease. Once the diagnosis is made, the possibility of complications such as pneumothorax, pulmonary hypertension and pulmonary fibrosis should be looked for on follow-up imaging.