Abstract

Background/Objectives: Beta-thalassemia (β-thal) is an inherited hemoglobin disorder caused by mutations in the HBB gene. Hb Malay (HBB:c.59A>G [NM_000518.5], p.Asn20Ser, CD19), a missense substitution (AAC→AGC; Asn→Ser) in exon 1 of the β-globin gene causing β+-thalassemia, has been mainly described in Southeast Asian populations but remains underreported in published Indonesian molecular epidemiology literature. This study aimed to identify the Hb Malay variant and investigate its familial segregation in a large Indonesian extended family. Methods: Cascade molecular screening was initiated following detection of the mutation in a proband referred for genetic testing. Sixteen individuals (one proband and 15 family members) consented to participate. Genomic DNA was extracted from peripheral blood and a 1.9-kb β-globin gene fragment was amplified by PCR. Mutation screening was performed using the Thalassemia GenoArray Kit HBGA-THAL-b31 (Hybribio) and confirmed by Sanger sequencing. A three-generation pedigree was constructed from molecular results and family interviews. Results: The Hb Malay mutation (HBB:c.59A>G) was identified in 13 of 16 individuals: 12 heterozygous carriers (A/G) and one homozygous individual (G/G, subject III-1, aged 15 years). Three individuals showed the normal genotype (A/A). Pedigree analysis demonstrated autosomal recessive inheritance across three generations. No α-globin deletions covered by the GenoArray panel were detected. Conclusions: To our knowledge, this is one of the few documented reports of cascade molecular screening for the Hb Malay (HBB:c.59A>G) variant in a large extended Indonesian family, confirmed by dual molecular methods. These findings illustrate the potential value of cascade molecular screening for early carrier identification in settings where hemoglobin fractionation testing is unavailable, and highlight the need for population-based epidemiological studies to guide thalassemia prevention policy in Indonesia.

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