Erdheim–Chester disease: A systematic review

• CNS involvement occurs in 56% of ECD patients.
• Concomitant pituitary involvement, retro-orbital and axial lesions suggest ECD diagnosis.
• Kidney infiltration is more frequent in patients with CNS involvement.

Erdheim–Chester disease (ECD) is a rare form of non-Langerhans-cell histiocytosis, associated in more than 50% of cases to BRAFV600E mutations in early multipotent myelomonocytic precursors or in tissue-resident histiocytes. It encompasses a spectrum of disorders ranging from asymptomatic bone lesions to multisystemic, life-threatening variants. We reviewed all published reports of histologically-confirmed ECD and explored clinical, radiological, prognostic and therapeutic characteristics in a population of 448 patients, including a unique patient from our Department. To find a clinically relevant signature defining differentiated prognostic profiles, the patients’ disease features were compared in relation to their CNS involvement that occurred in 56% of the entire population. Diabetes insipidus, visual disturbances, pyramidal and extra-pyramidal syndromes were the most recurrent neurological signs, whereas concomitant pituitary involvement, retro-orbital masses and axial lesions in the presence of symmetric bilateral osteosclerosis of long bones depicted the typical ECD clinical picture. Patients with CNS infiltration showed a lower occurrence of heart involvement and a higher incidence of bone, skin, retro-peritoneal, lung, aortic and renal infiltration. No difference in the therapeutic algorithm was found after stratification for CNS involvement. A better understanding of the disease pathogenesis, including BRAF deregulation, in keeping with improved prognostic criteria, will provide novel suggestions for the management of ECD.