Our national reference center for inherited metabolic diseases in La Pitié-Salpêtrière hospital (director, Prof. Mochel) focuses primarily on adult neurometabolic diseases. As a result, we follow most French adult patients with CTX. This chapter provides a summary of the natural history study of 14 French patients with CTX that emphasizes that most patients exhibit symptoms as children. This chapter also describes therapeutic outcomes of 13 French patients treated with chenodeoxycholic acid (CDCA) with standardized neurological and neuroimaging measures. As reported in other cohorts, neurological dysfunction can be halted, and even reversed, by metabolic intervention such as CDCA supplementation. Since not all adult patients with CTX develop neurological dysfunction, we need to identify sensitive biomarkers to detect brain disease activity before the onset of neuropsychiatric manifestations to guide therapeutic management.