In the current classification of the World Health Organization (WHO), bone marrow mastocytosis (BMM) is a provisional variant of indolent systemic mastocytosis (ISM) defined by bone marrow involvement and absence of skin lesions. However, no additional diagnostic criteria for BMM have been proposed. Within the registry dataset of the European Competence Network on Mastocytosis, we compared characteristics and outcomes of 390 patients with BMM and 1175 patients with typical ISM. BMM patients were significantly older, predominantly male, had lower tryptase and lower burden of neoplastic mast cells, and displayed a higher frequency of allergic reactions, mainly triggered by Hymenoptera, than patients with typical ISM. The estimated 10-year progression-free survival of BMM and typical ISM was 95.9% and 92.6%, respectively. In BMM patients defined by WHO-based criteria, the presence of one B-Finding and tryptase level ≥125 ng/mL were identified as risk factors for progression in multivariate analyses. BMM patients without any of these risk factors were found to have better progression-free survival (p < 0.05) and better overall survival (p < 0.05) than other ISM patients. These data support the proposal to define BMM as a separate SM variant characterized by SM criteria, absence of skin lesions, absence of B-Findings, and tryptase levels <125 ng/mL.

在世界卫生组织（WHO）当前的分类中，骨髓肥大细胞增多症（BMM）是惰性系统性肥大细胞增多症（ISM）的临时变体，定义为骨髓受累且无皮肤病变。然而，尚未提出 BMM 的额外诊断标准。在欧洲肥大细胞增多症能力网络的注册数据集中，我们比较了 390 名 BMM 患者和 1175 名典型 ISM 患者的特征和结果。与典型 ISM 患者相比，BMM 患者年龄明显较大，主要是男性，类胰蛋白酶较低，肿瘤性肥大细胞负担较低，并且主要由膜翅目引发的过敏反应频率较高。 BMM 和典型 ISM 的估计 10 年无进展生存率分别为 95.9% 和 92.6%。在根据 WHO 标准定义的 BMM 患者中，多变量分析将存在一项 B 超检查和类胰蛋白酶水平≥125 ng/mL 确定为进展的危险因素。与其他 ISM 患者相比，没有任何这些危险因素的 BMM 患者具有更好的无进展生存期 ( p < 0.05) 和更好的总生存期 ( p < 0.05)。这些数据支持将 BMM 定义为单独的 SM 变体的提议，其特征是 SM 标准、无皮肤损伤、无 B 超检查结果以及类胰蛋白酶水平 <125 ng/mL。