Adult leukoencephalopathies with prominent infratentorial involvement can be caused by Erdheim–Chester disease

Background Leukoencephalopathies with prominent involvement of cerebellum and brainstem, henceforward called prominent infratentorial leukoencephalopathies (PILs), encompass a variety of inherited and acquired white matter diseases. Erdheim–Chester disease (ECD) is a rare non-Langerhans cell histiocytosis likely under-diagnosed as cause of adult PIL. Methods We reviewed the clinical and laboratory information of ten consecutive sporadic adult patients with PIL of unknown origin, who were investigated for ECD. Results There were seven males and three females; mean age at clinical onset was 49.6 years (range 38–59); cerebellar ataxia with or without other neurological symptoms was the only or the main clinical manifestation; diabetes insipidus was present in three individuals. Eight patients had white matter focal supratentorial abnormalities, in addition to the infratentorial white matter changes. Six out of eight patients had spinal cord lesions. Thoraco-abdominal CT showed periaortic sheathing in two patients, whole-body FDG-PET revealed increased glucose uptake in the long bones of the legs in five patients, brain FDG-PET showed overt infratentorial hypermetabolism in one patient. In eight patients, ECD was confirmed by bone scintigraphy, pathological data, or both. Two ECD patients treated with vemurafenib showed a marked improvement of neurological symptoms and brain MRI abnormalities at 1 year follow-up. Conclusions Symptoms of PIL can be the only clinical manifestation of ECD. Adult patients with PIL of unknown origin should undergo investigations aimed at unveiling ECD, including bone scintigraphy and whole-body FDG-PET. The early diagnosis allows starting disease-modifying therapies of an otherwise life-threatening disease.