Erdheim-Chester Disease (ECD) is a rare histiocytosis. Multi-organ xanthogranulomatous infiltration occurs with clonal proliferation of myeloid precursor cells, frequently presenting BRAFV600E mutation. CNS involvement is considered an independent risk factor for worse prognosis, being described in 30-40% of patients.
A 64 years old woman presented to our department, with a 5 months history of diplopia, dysarthria, ataxia and a diagnosis of Diabetes Insipidus made 30 years earlier.
Brain MRI identified a contrast enhancing pontine lesion, extending to the cerebellar peduncles, hyperintense on T2, first considered a malignant glial lesion.
A biopsy sample was obtained, showing glial tissue and Rosenthal fibres, without evidence of inflammatory infiltrate or malignant tissue. After a posterior complaint of lower limb osseous pain, a bone scintigraphy was ordered, followed by a PET-FDG, describing metaphyseal and diaphyseal, bilateral and symmetrical involvement of tibia and femur, a finding characteristic of ECD, confirmed by bone lesion biopsy.
Targeted therapy was instituted with vemurafenib, being suspended two months later due to intolerable toxicity. Nevertheless, complete remission was observed on brain MRI. An association of dabrafenib and trametinib was started, being suspended after one month due to toxicity.
Despite having presented complete remission on MRI scans, PET-FDG still showed pontine metabolic activity.
After 17 months, a contrast enhancing lesion has reappeared, leading to reinstitution of therapy with dabrafenib.