The purpose of this observational study is to assess the real-world safety of luspatercept in Korean participants with myelodysplastic syndrome (MDS) or beta thalassemia. Investigators will enroll participants who will begin treatment with at least 1 dose of luspatercept.

Inclusion Criteria:

• Adult participants 19 years of age or older
• Participants who will be treated with luspatercept according to the approved label in the Republic of Korea
• Participants who sign the informed consent form

Exclusion Criteria:

• Participants who are prescribed luspatercept for therapeutic indications not approved in the Republic of Korea
• Participants for whom luspatercept is contraindicated as clarified in the Korean prescribing information approved by the Ministry of Food and Drug Safety

Adults with transfusion-dependent anemia associated with very low, low, and intermediate-risk myelodysplastic syndrome with ring sideroblasts (MDS-RS) or MDS/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) who had an unsatisfactory response to, or are ineligible for erythropoietin-based therapy, and adults with transfusion-dependent anemia associated with beta thalassemia, who will begin therapy with luspatercept.