# Abnormal hemoglobin anti-Lepore Hong Kong compound with β0-thalassemia ameliorate thalassemia severity when co-inherited with α-thalassemia

## TL;DR

A rare hemoglobin variant combined with thalassemia can reduce disease severity when inherited with another type of thalassemia.

## Contribution

First identification of compound heterozygotes involving anti-Lepore Hong Kong, β0-thalassemia, and α-thalassemia.

## Key findings

- Anti-Lepore Hong Kong heterozygotes showed average HbA2 level of 17.7% and normal behavior.
- Compound heterozygotes showed higher HbA2 levels (30.2–40.8%) and β-thalassemia trait.
- α/β-mRNA ratio indicated slight β-globin downregulation similar to β-thalassemia minor.

## Abstract

Abnormal hemoglobin anti-Lepore Hong Kong is a rare βδ fusion variants resulting from non-homologous crossover during meiosis. Anti-Lepore Hong Kong is known to consistently exhibit significantly increased level of HbA2. In this study, we used multiplex ligation-dependent probe amplification (MLPA) and single molecular real-time (SMRT) sequencing, as well as Sanger sequencing, to identify variants in five unrelated families with abnormal elevated HbA2 level. All probands in these five families were found to be heterozygous for anti-Lepore Hong Kong. Among them, two families showed co-occurrence of β0-thalassemia and α-thalassemia (–SEA/ or αCSα/). Heterozygotes for anti-Lepore Hong Kong displayed an average HbA2 level of 17.7% and behaved normal. However, when combined with β0-thalassemia and α-thalassemia, the probands exhibited higher HbA2 level (30.2–40.8%) and behaved with β-thalassemia trait. Furthermore, determination of the α/β-mRNA ratio revealed a slight downregulation of β-globin, similar to that of β-thalassemia minor. Our study is the first to identify compound heterozygotes for anti-Lepore Hong Kong, β0-thalassemia and α-thalassemia, provide valuable information for prenatal counseling.