Multiorgan histiocytosis after B-cell acute lymphoblastic leukemia

The association of multiorgan histiocytosis after acute lymphoblastic leukemias is very rare as most cases are localized forms of Langerhans cell histiocytosis (LCH). We report on an 18-year-old man diagnosed with B-cell acute lymphoblastic leukemia (B-ALL) with p16 deletion (9p21). He was treated with induction chemotherapy using the Spanish PETHEMA group protocol and achieved complete remission. Three months after the diagnosis of B-ALL, he developed a severe multiorgan histiocytosis that is clinically suggestive of LCH but lacked typical immunohistochemical features of LCH and indeterminate cell histiocytosis: CD1a was strongly positive, CD68 and S-100 protein were moderately positive, and langerin was negative. The drugs of the first-line treatment recommended for LCH had been part of the chemotherapy of B-ALL that the patient had received. Therefore, we prescribed the second-line treatment for LCH (cytarabine and 2'-chlorodeoxyadenosine), and he achieved partial remission. The patient died during the aplasia induced by the third cycle of chemotherapy from pneumonia. We could not demonstrate the transdifferentiation of tumoral lymphocytes into histiocytes, using p16 deletion (9p21) as a marker, because these cells did not share the mutation. Neither could we study immunoglobulin-H rearrangement as we had exhausted all the tissue samples. In the medical literature, there are a few reported cases of T-cell acute lymphoblastic leukemia followed by disseminated LCH and just 1 case of B-ALL followed by localized LCH affecting the bones. Therefore, our patient may be the first published case of B-ALL followed by histiocytosis, which had 2 singularities: it was multiorgan and the immunohistochemistry was not typical of LCH.