Spontaneous remission of 2-chlorodeoxyadenosine (2-CdA)-related secondary myelodysplastic syndrome in a patient with refractory Langerhans cell histiocytosis.

Langerhans cell histiocytosis (LCH) is sometimes resistant to conventional chemotherapies, and treatment with 2-chlorodeoxyadenosine (2-CdA) is gaining importance as a salvage treatment for refractory or recurrent LCH. Secondary malignancies such as acute myelogenous leukemia and myelodysplastic syndrome (MDS) due to 2-CdA have recently been reported. However, there have been no reports to date of cases of 2-CdA-related secondary MDS in which spontaneous remission was achieved. Here, we report the case of a 1-year-old boy with an occipital tumor who was diagnosed with LCH by biopsy and underwent chemotherapy. However, the disease relapsed and became refractory to chemotherapy. He received 2-CdA treatment, which was effective. However 6 months after the start of treatment, he developed MDS with chromosomal abnormality of 7q-. After 1-year observation without any intervention, his hematological findings had returned to normal, and the chromosomal abnormality had also disappeared. To our knowledge, this is the first report of 2-CdA-related MDS with spontaneous hematological remission.