KL-6: marker for pulmonary involvement in Langerhans cell histiocytosis in infants.

The purpose of this study was to investigate serum KL-6 levels in an infant with Langerhans cell histiocytosis (LCH) and pulmonary involvement. The histologic diagnosis of LCH was established by skin biopsy. Imaging of the chest confirmed marked interstitial shadowing throughout both lung fields. Acutely, serum KL-6 was elevated to 9,400 U/mL. Following induction chemotherapy, clinical manifestations of LCH improved and the levels of serum KL-6 returned to within normal limits. During the maintenance therapy phase, there was a resurgence of the LCH, but without involvement of the lungs, and the levels of KL-6 remained normal. The authors conclude that KL-6 may be a useful marker for pulmonary involvement in infants with LCH.