MEK Inhibition in the Treatment of Congenital Langerhans Cell Histiocytosis: A Case Report and Review of the Literature.

Langerhans cell histiocytosis (LCH) is a histiocytic disorder that predominantly affects young children, with congenital manifestations being exceedingly rare. Here, we report a male infant with congenital LCH harboring a driving mutation within the mitogen-activated protein kinase pathway, specifically MAP2K1 Q56P. First-line use of targeted therapy with oral MEK inhibitor trametinib led to rapid and complete resolution of the infant's widespread cutaneous disease. This patient remains clinically well with normal growth and development and no sign of progressive disease or medication intolerance. This case demonstrates the impact that targeted therapy can have as an alternative to systemic chemotherapy in an age group known to experience more extensive disease.