A case report released on Apr. 13 describes the treatment of an elderly woman who developed mixed histiocytosis (Langerhans cell histiocytosis and Erdheim-Chester disease) after multiple relapses of skull Langerhans cell histiocytosis. The patient’s condition was successfully managed with targeted BRAF and MEK inhibitors after standard chemotherapy proved ineffective.
The report highlights that mixed histiocytosis developing after initial treatment for skull LCH is not widely recognized, making this case notable for clinicians treating similar disorders. Early identification and appropriate therapy may be important for patients with a history of recurrent LCH lesions.
According to the report, the patient first experienced polyuria and polydipsia five years before her diagnosis of unifocal LCH in the left temporal bone, which was surgically removed. Two years later, she suffered a relapse in the right parietal skull, where testing confirmed a BRAF V600E mutation; she then received chemotherapy. Subsequent relapses occurred in both cranial bones and finally at the L2 vertebra in her spine. Biopsy at this stage revealed features consistent with both LCH and ECD—termed mixed histiocytosis—which did not respond to conventional treatments but showed complete metabolic response to dabrafenib/trametinib therapy.
The article notes that most cases of these rare disorders harbor mutations affecting the MAPK pathway such as BRAF V600E, and that central diabetes insipidus can precede diagnosis by several years due to pituitary involvement. Mixed histiocytosis is increasingly reported in medical literature, often arising from a common progenitor cell according to recent hypotheses.
While series have described median delays of four years between initial LCH diagnosis and development of mixed disease such as ECD/LCH combinations, responses to traditional therapies are generally poor while targeted agents like BRAF/MEK inhibitors offer better outcomes. In this particular case, cladribine produced only partial remission before targeted therapy led to full metabolic response; however, it remains unclear if cladribine contributed significantly.
The authors caution that limitations include its status as a single case study with short follow-up duration for assessing long-term efficacy or recurrence risk.
