A 61-year-old man developed progressive gait imbalance and papular skin lesions over 9 months. He reported fatigue, but no other constitutional symptoms. Neurologic examination revealed gait ataxia. Brain MRI (figure 1, A–D) demonstrated punctate enhancing foci supratentorially and patchy pontine T2 hyperintensity; no pituitary or orbital abnormality was reported. Skin biopsy (figure 2) revealed a histiocytic neoplasm that stained negative for CD1a, weakly positive for S100, and positive for CD163, factor 13A, and BRAF V600E, compatible with Erdheim-Chester disease.1 Bone scan and body PET did not demonstrate osseous, cardiac, lung, or retroperitoneal involvement. Vemurafenib was prescribed for Erdheim-Chester disease with brain and skin involvement.2 Brain involvement occurs in up to half of patients with Erdheim-Chester disease and most often manifests radiographically as pontine or cerebellar T2 hyperintensity, although multifocal punctate enhancement has also been reported.3,4 Skin involvement is observed in approximately one-quarter of patients and lesions are most commonly xanthelasma-like, although nonfacial cutaneous xanthoma-like lesions as seen in our patient may also occur.5 On follow-up 4 months later, the patient’s skin lesions had flattened, gadolinium enhancement had resolved, and pontine T2 hyperintensity had nearly resolved (figure 1, E and F), although gait imbalance persisted.