Summary Next‐generation sequencing has shed light on the diagnosis of previously unsolved cases of inherited haemolytic anaemia (IHA). We employed whole‐exome sequencing to explore the molecular diagnostic spectrum of 21 unrelated Thai paediatric patients with non‐thalassemic IHA, presenting hydrops fetalis and/or becoming transfusion‐dependent for 1 year or more or throughout their lifespan. Anaemia was detected prenatally, within the first month and the fifth year of life in three, 12 and six patients respectively. Molecular diagnosis obtained from all patients revealed SPTB as the most frequently mutated gene (four reported, three novel), found in 31 of 42 studied alleles. The other two mutated genes identified were ANK1 (three novel) and KLF1 (two reported). Four recurring mutations within exon 29/30 (NM_001024858.2) accounted for the vast majority (90%) of mutated SPTB alleles, biallelic inheritance of which resulted in the most severe phenotypes: hydrops fetalis and life‐long transfusion dependency. Dominant ANK1 (n = 3) and SPTB (n = 2) mutations and biallelic class 2 KLF1 mutations (n = 1) led to a shorter period of transfusion dependency. Our study demonstrated that mutated SPTB causing red‐cell membranopathy is likely the most common cause of severe non‐thalassemic IHA among Thai patients. This urges carrier screening in the population to prevent subsequent, severely affected births.

Background Reticulocyte hemoglobin equivalent (Ret‐He), a direct measure of the hemoglobin (Hb) in the young red blood cells, has been reported to be useful in the diagnosis of iron deficiency anemia (IDA) but may have some limitations in thalassemia trait. This study evaluated the differences in Ret‐He in school‐aged children, and assessed the diagnostic value of Ret‐He in identifying IDA in a thalassemia‐prevalent area. Methods Blood samples underwent complete blood count analysis, including Ret‐He, ferritin, serum iron and total iron binding capacity. Blood samples also underwent Hb typing and a molecular study for α‐thalassemia. Receiver operating characteristic analysis was performed to determine the predictive capacity of Ret‐He in the diagnosis of IDA. ID was defined as serum ferritin <30 ng/mL and/or transferrin saturation (TSAT) <16%; IDA was defined as serum ferritin <12 ng/mL and/or TSAT <16% with low Hb for age. Normal healthy children (normal controls: NC) had normal iron study, without the thalassemia trait. Results Ninety‐eight children with a mean age of 12.9 ± 0.6 years were included. Ret‐He in the thalassemia trait group (26.7 ± 2.4 pg), ID group (29.0 ± 2.9 pg), IDA group (25.4 ± 2.7 pg), ID + thalassemia trait group (26.6 ± 2.8 pg), and the IDA + thalassemia trait group (24.6 ± 2.3 pg) was significantly lower than in the NC group (30.8 ± 1.7 pg; P < 0.001, 0.01, 0.006, 0.002 and <0.001, respectively). Ret‐He had an area under the curve of 0.904 in diagnostic ability for IDA, while a cut‐off ≤27 pg had a sensitivity of 91.7% and a specificity of 81%. Conclusion Ret‐He was lowest in subjects with IDA + thalassemia trait. A Ret‐He cut‐off ≤27 pg was suggestive of IDA in the present study.

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