Asian Journal of Pediatric Research

Introduction :  Langerhans cell histiocytosis (LCH) is a rare clonal disorder of dendritic cells with heterogeneous clinical manifestations, ranging from isolated bone lesions to severe multisystemic disease. Its association with Evans syndrome, defined by autoimmune haemolytic anaemia and immune thrombocytopenia, is extremely uncommon in paediatric patients.

Observation : We report the case of a 16-month-old girl admitted for bicytopenia. Clinical findings included pallor, an erythematous, squamous rash, splenomegaly, and bone involvement with vertebral collapse. Laboratory evaluation revealed autoimmune haemolytic anaemia with thrombocytopenia, confirmed by a positive Coombs test,elevated LDH levels and indirect hyperbilirubinaemia. Imaging demonstrated thymic hypertrophy, lytic skull lesions, and paravertebral tissue infiltration. A skin biopsy confirmed LCH with CD1a and PS100 positivity, and molecular analysis identified an activating MAPK/ERK pathway mutation. The patient was treated according to a high-risk LCH protocol with vinblastine and systemic corticosteroids, resulting in a favourable outcome both clinically and biologically.

Conclusion: This case illustrates the rarity of the LCH–Evans association and highlights the importance of considering autoimmune mechanisms in cytopenias occurring during LCH. The identification of a MAPK/ERK pathway mutation further suggests a potential link between histiocytic proliferation and immune dysregulation.