HbS/β+ thalassemia: Really a mild disease? A National survey from the AIEOP Sickle Cell Disease Study Group with genotype-phenotype correlation

Objectives: HbS/β+ patients’ presence in Italy increased due to immigration; these patients are clinically heterogeneous, and specific guidelines are lacking. Our aim is to describe a cohort of HbS/β+ patients, with genotype-phenotype correlation, in order to offer guidance for clinical management of such patients. Methods: Retrospective cohort study of HbS/β+ patients among 15 AIEOP Centres. Results: A total of 41 molecularly confirmed S/β+ patients were enrolled (1-55years, median 10.9) and classified on β+ mutation: IVS-I-110, IVS-I-6, promoter, and “others.” Prediagnostic events included VOC 16/41 (39%), ACS 6/41 (14.6%), sepsis 3/41 (3.7%), and avascular necrosis 3/41 (7,3%). Postdiagnostic events were VOC 22/41 (53.6% %), sepsis 4/41 (9.7%), ACS 4/41 (9.7%), avascular necrosis 3/41 (7.3%), aplastic crisis 2/41 (4.8%), stroke 1/41 (2.4%), ACS 1/41 (2.4%), and skin ulcerations 1/41 (2.4%). The IVS-I-110 group presented the lowest median age at first SCD-related event (P=.02 vs promoter group) and the higher median number of severe events/year (0.26 events/patient/year) (P=.01 vs IVS-I-6 and promoter groups). Promoter group presented a specific skeletal phenotype. Treatment regimen applied was variable among the centers. Conclusions: HbS/β+ is not always a mild disease. Patients with IVS-I-110 mutation could benefit from a standard of care like SS and S/β° patients. Standardization of treatment is needed.