The Nationwide Study of Erdheim-Chester Disease in Japan

Background: Erdheim-Chester disease (ECD) is a subtype of non-Langerhans histiocytic disorder that is shown to be driven by hyperactivation of MAPK pathway (most frequently caused by BRAFV600E mutation) and characterized by generalized organ dysfunction with infiltration of CD68-positive, CD1a-negative histiocytes. However, ECD is a rare entity and therefore very little is known about epidemiology of this disorder.

Methods: We underwent a postal questionnaire-based, multi-center retrospective study to clarify the clinical features of ECD patients. We first sent 3850 questionnaires to various departments including orthopedics, respiratory medicine, dermatology, hematology, and pathology to cover as many ECD patients as possible, and identified 71 ECD patients in Japan. We further collected detailed clinical information and patients' samples if available. All cases were pathologically proven and the diagnoses of ECD were self-reported by each institute. DNA was extracted from each clinical sample and Sanger sequencing or allele-specific polymerase chain reaction (PCR) for BRAFV600E mutation were underwent with specific primers.

Results: Among 71 patients with ECD, detailed clinical information about 38 patients were collected. The median age was 51 years old (range: 25-76 years old) and there was a male predominance (1.9:1). Major affected lesions were the bone (84 %), central nervous system (CNS; 50 %), cardiovascular lesion (37 %), skin (37 %), retroperitoneum (37 %), endocrines (37 %), lung (24 %), and digestive organ (12 %). C-reactive protein at onset was higher than upper normal limit in 24 of 29 patients (median 23.8 mg/L). The median time from the onset to diagnosis was 17 months and median survival from initial onset was 10.9 years. In the univariate analyses, age older than 60 years old at initial onset (hazard ratio [HR], 30.2; 95% CI, 5.7-159; p < 0.001), weight loss (HR, 5.4; 95% CI, 1.4-20.8; p = 0.014), CNS involvement (HR, 25.2; 95% CI, 3.1-203; p = 0.0024), cardiovascular lesion (HR, 3.6; 95% CI, 1.2-10.8; p = 0.021) and digestive organ disease (HR, 5.6; 95% CI, 1.6-20.2; p = 0.0085) were associated with poor prognosis. Interestingly, the bone involvement was associated with better outcome (HR, 0.20; 95% CI, 0.065-0.63; p = 0.0052). Multivariate analysis revealed that older age was an independent poor prognostic factor (HR, 18.9; 95% CI, 2.12-169; p = 0.0085). In addition, patients with CNS involvement were significantly older than patients without CNS disease (median, 63.7 vs 44.0 years old; p < 0.001). We also analyzed the BRAF V600E mutation status in seven cases. Allele-specific PCR identified that three of seven patients had BRAFV600E mutation.

Conclusion: Our nationwide survey revealed that older age was associated with CNS involvement and poor prognosis in ECD patients. In addition, the bone, cardiovascular, CNS and digestive organ involvement might also affect clinical outcome. It is of note that the bone lesion was associated with better survival in the univariate analysis. However, larger and prospective studies are warranted. Regional disparity such as percentage of bone lesions should be also investigated.