CHARACTERISTIC BRAIN MRI APPEARANCE OF ERDHEIM-CHESTER DISEASE

Erdheim-Chester disease (ECD) is a rare, non-Langerhans cell histiocytosis of unknown origin characterized by systemic infiltrates of non-Langerhans histiocytes, usually involving multiple organs, including CNS.1–3 Skeletal involvement is considered highly specific and typical radionuclide bone scan findings include bilateral, symmetric increased tracer uptake in the metaphyses and diaphyses of the long bones, mainly femur and tibiae, with epiphyseal sparing.3 Once suspected in the living patient, the diagnosis of ECD needs to be confirmed by surgical biopsy of the affected tissues. Clinical manifestations are protean4 and in cases with neurologic involvement MRI can help diagnosis.5 We report 2 cases of adult-onset ECD with neurologic involvement and strikingly similar brain MRI pattern of abnormalities. ### Case 1. A 65-year-old man was admitted with a 4-year history of progressive loss of coordination and balance. He had had central diabetes insipidus for 3 years. Neurologic examination showed cerebellar ataxia and pyramidal signs. Dysarthria and dysphagia were also present, suggesting possible supranuclear bulbar involvement. Sensory, cognitive functions, and cranial nerves were normal. Biochemical parameters, including serum sodium, potassium, magnesium, and phosphate levels, were normal. A brain MRI showed diffuse hyperintensity in the pons extending to the left middle cerebellar peduncle and lower midbrain (figure, A). Diffuse hyperintensity of the periventricular white matter and thickening of the pituitary stalk were also evident. Bone radiographs showed bilateral, symmetric …