Association of Hb Thailand [α56(E5)Lys→Thr] and Hb Phnom Penh [α117(GH5)-Ile-α118(H1)] withα⁰-Thalassemia: Molecular and Hematological Features and Differential Diagnosis

Abstract

We report the molecular and hematological characteristics of two rare hemoglobin (Hb) variants found in associations with a common α(0)-thalassemia (α(0)-thal) in Thai patients. The first case (P1) was a generally healthy 27-year-old man discovered during our ongoing thalassemia screening program. Hemoglobin and DNA analyses identified a previously undescribed condition of compound heterozygosity for Hb Thailand [α56(E5)Lys→Thr] and α(0)-thal (SEA deletion). The second case (P2) was a 4-year-old boy with hypochromic microcytic anemia. Hemoglobin and DNA analyses also identified a compound heterozygosity for Hb Phnom Penh [α117(GH5)-Ile-α118(H1)] in association with α(0)-thal (SEA deletion). Although Hb H (β(4)) inclusion bodies were observed in both cases, Hb analysis using both high performance liquid chromatography (HPLC) and capillary electrophoresis (CE) did not show Hb H. While the two Hb variants could be recognized on Hb HPLC analysis, their corresponding Hb A(2) derivatives: the Hb A(2)-Thailand and Hb A(2)-Phnom Penh, were clearly observed on CE. Apparently, combination of these two Hb variants with α(0)-thal are not expressed as Hb H disease. The two Hb variants could be confirmed by polymerase chain restriction-restriction fragment length polymorphism (PCR-RFLP) and allele-specific PCR assays.

A Large Cohort of Hemoglobin Variants in Thailand: Molecular Epidemiological Study and Diagnostic Consideration

“…The latter three Hb variants have been described in detail separately [26]–[28]. Hb separation profiles on HPLC and capillary electrophoresis of the remaining 4 Hb variants were presented in Figure 3 .…”

“…Association of this Hb variant with α 0 -thalassemia leads to the α-thalassemia disease known as Hb QH disease [31]. We have described in details of other Hb variants including Hb Siam (α1 15GGT-CGT, Gly-Arg ), Hb Queens (α1 34CTG-CGG, Leu-Arg ), Hb Beijing (α2 16AAG-AAC, Lys-Asn ), Hb Hekinan (α1 27GAG-GAC, Glu-Asp ), Hb Thailand (α 56AAG-ACG, Lys-Thr ), Hb St. Luke’s-Thailand (α2 95CCG-CGG, Pro-Arg ), Hb Phnom Penh (α1 117/118, Ile insertion ) and Hb Nakhon Ratchasima (α2 63GCC-GTC, Ala-Val ) previously [13], [21]–[23], [26], [27]. The remaining Hb variants namely Hb Q-India (α1 64GAC-CAC, Asp-His ), Hb Dunn (α 6GAC-AAC, Asp-Asn ), Hb G-Honolulu (α 30GAG-CAG, Glu-Gln ) and Hb J-Wenchang-Wuming (α1 11AAG-CAG, Lys-Gln ), rarely been found in our population, are briefly described here.…”

Interaction of hemoglobin Grey Lynn (Vientiane) with a non-deletional α+-thalassemia in an adult Thai proband

“…Testing for the presence of α 0 -thalassemia (-- SEA and -- THAI ), α + -thalassemia (−α 3.7 and −α 4.2 ), Hb Constant Spring (α CS α or HBA2:c.427T>C) and Hb Pakse’ (α PS α or HBA2:c.429A>T) commonly found in Thailand, was performed using polymerase chain reaction (PCR) based methods as described elsewhere (13,14). Previously described multiplex allele specific PCR assays were used to check the presence of mutations detected in patients previously referred to our laboratory: Hb Hekinan [α27(B8)Glu → Asp or HBA2:c.84G>C], Hb Nakhon Ratchasima [α63(E12)Ala → Val or HBA2:c.191C>T] and Hb Phnom Penh [α117(GH5)-Ile-α118(H1) or HBA1:p. Phe118_Thr119insIle] (15,16). DNA sequencing of amplified α1- and α2-globin genes were performed using specific primers and an ABI PRISM TM 3130 XL analyzer (Applied Biosystems, Foster City, CA, USA) (17).…”

A rare haemoglobin variant (Hb Phnom Penh) manifesting as a falsely high haemoglobin A1c value on ion-exchange chromatography

“…In previously reported cases, both patients showed the interaction of this a-chain variant with a common Southeast Asian deletion mutation. (7,9) Routine blood tests revealed microcytic anaemia, alerting physicians to this genetic variant associated with thalassaemia. However, there is no report addressing the impact of this silent Hb variant on the measurement of HbA1c.…”

“…(6) Thereafter, Hb Phnom Penh was reported in the Chinese, Taiwanese and Thais. (7)(8)(9) By means of isopropanol precipitation and heat instability tests, Hb Phnom Penh has been proven to be a nonpathological variant. In previously reported cases, both patients showed the interaction of this a-chain variant with a common Southeast Asian deletion mutation.…”