骨髓增生异常综合症 (旧称白血病前期；英文：myelodysplastic syndromes，缩写MDS)，又译为骨髓发育不良症候群、骨髓生成不良症候群，是一组血液的异质性疾病，是由于骨髓性的造血干细胞的无效性增生（或不典型增生）所导致的血液病。

MDS患者通常会出现严重的贫血，需要频繁输血。在大多数情况下，MDS最终会导致患者发展成由于骨髓造血功能衰竭所引起的血细胞减少症。大约三分之一的MDS患者，经过几个月到几年的时间，MDS就可以发展成为急性骨髓性白血病。

MDS起源于造血干细胞。在MDS患者中，造血功能呈现病态造血（无规则且无序），从而导致造血细胞的数量和质量的不可逆转的下降​​，从而进一步阻碍血液的制造。

The myelodysplastic syndromes (also known as MDS or myelodysplasia) are hematological (i.e., blood-related) medical conditions with ineffective production (or "dysplasia") of all blood cells.

Patients with MDS can develop severe anemia and require blood transfusions. In some cases, the disease worsens and the patient develops cytopenias (low blood counts) caused by progressive bone marrow failure. The outlook in MDS depends on the type and severity. Many people live normal lifespans with MDS.