Hemoglobin Tak in a newborn Malay

Compound heterozygous Hb Tak/Hb E causes secondary erythrocytosis in a Thai family

Hb Tak is a rare cause of secondary erythrocytosis. It results from the insertion of two nucleotides (AC) at the termination codon between codon 146 and codon 147 of the beta-globin gene. This insertion causes a frameshift in the terminating codon 147 resulting in an elongated beta chain with an impaired formation of the T-state. We report a Thai family with a compound heterozygosity for Hb Tak [beta147 (+ AC)] and Hb E [beta26(B8)Glu-->Lys] which displayed an asymptomatic erythrocytosis.

Multiplex allele-specific PCR assay for differential diagnosis of Hb S, Hb D-Punjab and Hb Tak

BACKGROUND

Apart from hemoglobin (Hb) E, Hb D-Punjab [beta121(GH4)Glu-Gln] and Hb Tak [beta147Term-Thr] are the two most common beta-chain variants among the Asian population. These two Hb variants have similar alkaline electrophoretic mobilities and HPLC profiles as those of the Hb S [beta6(A3)Glu-Val]. Differential diagnosis of these clinically relevant hemoglobinopathies is therefore problematic. Direct detection of the beta-globin gene mutations would be another diagnostic alternative.

METHODS

A simultaneous DNA diagnosis of the three Hb variants was developed based on the multiplex allele-specific polymerase chain reaction (PCR) approach. The method was validated on 10 carriers of Hb D-Punjab, 5 carriers of Hb Tak, 2 carriers of Hb S and 50 normal individuals of Thai origin.

RESULTS

The three abnormal Hbs could be correctly diagnosed with the simultaneous PCR approach, and a complete concordance with results using other established methods was obtained.

CONCLUSIONS

The multiplex allele-specific PCR approach developed should prove useful in complementing routine Hb analysis for differential diagnosis of these three common Hb variants and should facilitate a program of hemoglobinopathy screening in the region.

Homozygous hemoglobin Tak causes symptomatic secondary polycythemia in a Thai boy

Secondary polycythemia caused by high-oxygen-affinity hemoglobin is rare in children. Most patients with this condition have asymptomatic erythrocytosis. In this article the authors describe a young boy from Thailand with plethora, hypoxemia, and aggravated respiratory distress following a chest infection. Hematological and molecular studies revealed that the boy is homozygous for Hb Tak, an extended beta-globin variant with high oxygen affinity. This report of a patient who is homozygous for high-oxygen-affinity hemoglobin highlights the clinical significance of this hemoglobin disorder, which has been previously reported in several unrelated families from Southeast Asia.