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  Table of Contents    
CASE REPORT  
Year : 2016  |  Volume : 59  |  Issue : 1  |  Page : 99-101
Hemoglobin Agenogi - A rare abnormal beta globin chain variant


1 Department of Pathology, Lady Hardinge Medical College and Hospital, New Delhi, India
2 Department of Pediatrics, Lady Hardinge Medical College and Hospital, New Delhi, India
3 Department of Hematogenetics, National Institute of Immunohematology, Mumbai, Maharashtra, India

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Date of Web Publication9-Mar-2016
 

   Abstract 

Haemoglobin (Hb) Agenogi is clinically asymptomatic, rare β-globin chain variant characterized by a substitution of glutamic acid by lysine at position 90 of β-chain. It elutes in the C-window on high-performance liquid chromatography (HPLC). We report a 10-year-old male with easy fatigability, lethargy, pallor, and mild splenomegaly. Hematological parameters revealed microcytic hypochromic anemia and mildly raised red blood cells count, suggestive of thalassemia trait. On HPLC, a predominant peak was observed in the C-window (82.6%) along with raised HbA 2 level (9.3%). Based on these findings, a possibility of HbC disease/β-thalassemia trait doubly heterozygous was considered. Family studies were advised. HPLC findings in father were suggestive of β-thalassemia trait, while both his mother and brother had an abnormal peak in the C-window of 42.7% and 40.8%, respectively, with elevated HbA 2 values of 5% and 4.9%, respectively. Direct DNA sequencing revealed intervening sequences 1-5 (G ; C) in father, confirming β-thalassemia trait. His mother and brother had heterozygous gene mutation at codon 90 of β-globin chain (G ; A) suggestive of Hb Agenogi. The child carried mutations for both β-thalassemia trait as well as Hb Agenogi.

Keywords: Agenogi, beta, variant

How to cite this article:
Sharma S, Sharma G, Chandra J, Colah R. Hemoglobin Agenogi - A rare abnormal beta globin chain variant. Indian J Pathol Microbiol 2016;59:99-101

How to cite this URL:
Sharma S, Sharma G, Chandra J, Colah R. Hemoglobin Agenogi - A rare abnormal beta globin chain variant. Indian J Pathol Microbiol [serial online] 2016 [cited 2019 Nov 17];59:99-101. Available from: http://www.ijpmonline.org/text.asp?2016/59/1/99/174844



   Introduction Top


Hemoglobinopathies are inherited disorders of globin, the protein component of haemoglobin (Hb). They are the most common genetic defects worldwide and provide a major diagnostic challenge. [1],[2] Newer diagnostic modalities such as DNA mutation testing have made a major breakthrough in our understanding and detection of the variant hemoglobins. In addition to the laboratory investigations, family study plays a crucial role in the complete work-up of these cases.


   Case report Top


We report a 10-year-old male of North Indian ethnicity residing in Delhi, who presented in the paediatrics outpatient department at Kalawati Saran Children's Hospital with easy fatiguability, lethargy for 2 years and a past history of jaundice 1-year back that was not brought to medical attention. Physical examination revealed pallor and mild splenomegaly (1 cm below the costal margin). Liver and renal function tests were within normal limits. His hemogram revealed moderate microcytic hypochromic anemia with mildly raised red blood cell count [Table 1]. Wright-stained peripheral smear revealed microcytic hypochromic red cells with mild anisopoikilocytosis. A few leptocytes, target cells, and polychromatophils were seen [Figure 1]. Serum iron studies and ferritin were within normal limits, excluding iron deficiency.
Figure 1: Wright - stained peripheral smear shows microcytic hypochromic red cells, a few leptocytes, target cells and polychromatophils

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Table 1: Hemogram and HPLC findings in the family


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Thus, a possibility of thalassemia minor was considered. Cation exchange high-performance liquid chromatography (HPLC) performed using Bio-Rad Variant II (Bio-Rad Laboratories, Hercules, USA) instrument revealed a predominant peak in the C-window with 82.6% area and retention time (RT) of 5.04 min along with high HbA 2 of 9.3% (RT 3.70 min). Thus, a possibility of HbC disease/β-thalassemia trait doubly heterozygous was considered and the family study was carried out.

The child's father, mother and younger brother were asymptomatic. Complete blood counts with peripheral smear examinations and HPLC were performed in all the family members [Table 1], [Figure 2] and [Figure 3]. The father's hemogram as well as chromatogram findings were suggestive of β-thalassemia trait. HPLC's of the mother and brother were similar and showed peak in C-window along with raised HbA 2 . Although the mother's raised HbA 2 might have been explained by concomitant megaloblastic anemia, this appeared unlikely in the sibling. Thus, the possibility of the index case being doubly heterozygous for HbC trait and β-thalassemia trait was considered. Peripheral smear review revealed no HbC crystals.
Figure 2: High - performance liquid chromatography chromatogram of the patient

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Figure 3: High - performance liquid chromatography chromatogram of the index case's mother

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For further confirmation, direct DNA sequencing of the entire family was carried out at the National Institute of Immunohematology, Mumbai. It confirmed β-thalassemia trait intervening sequences (IVS) (IVS 1-5 [G ® C]) in the father. Both the mother and brother had a β-globin gene mutation at codon 90 (G ® A), suggestive of Hb Agenogi. The patient's DNA sequencing revealed β-globin gene mutations IVS 1-5 (G ® C) as well as Codon 90 (G ® A) confirming double heterozygous state for β-thalassemia trait and Hb Agenogi.


   Discussion Top


Hb Agenogi is a β-chain variant characterized by a substitution of glutamic acid by lysine at position 90 of the β-chain. It was first described in 1966 by Miyaji et al. in a Japanese family. [3] This variant is characterized by slightly reduced oxygen affinity and is not associated with any appreciable clinical manifestations even if present in combination with β-thalassemia. Previous functional studies have shown that the interaction of the 890 Lys residue of Hb Agenogi with the C-terminal carboxyl group of the same β-chain shifts the equilibrium toward the deoxy form of Hb with lowering of the oxygen affinity. However, this shift is too small to cause clinical symptoms. [4] In our case too, the patient's mother and brother having Hb Agenogi trait were asymptomatic. However, the patient who was doubly heterozygous for β-thalassemia trait and HbAgenogi presented with nontransfusion-dependent moderate anemia.

On alkaline electrophoresis, Hb Agenogi migrates with HbA 2 and HbC and hence, it cannot be differentiated from HbC by this technique. [5] Other hemoglobins which co-elute in the C-window and should be excluded include HbC, Hb O-Arab, Hb Siriraj and Hb Constant Spring. [6],[7] A few case reports of this variant are available in the literature. [3],[4],[5],[8],[9] All these reports showed the abnormal hemoglobin ranged from 36% to 45% with HbA 2 varying from 2.5-3.2% in the carrier state while in our case HbA 2 values were raised (4.9-5%) in the carrier state. These raised values of HbA 2 were probably due to glycated adducts of the abnormal hemoglobin eluting in HbA 2 window. In a single study, when it is doubly heterozygous with β-thalasssemia trait, the predominant peak was of abnormal hemoglobin 89.8% with HbA 2 9.3% while in our case, it was 82.6% with HbA 2 9.3%, higher than the upper limit for β-thalassemia trait. This predominant peak was due to the interaction of β-thalassemia gene with that of the abnormal hemoglobin variant. [5] In India, Hb Agenogi has been previously reported only in an Indian Council of Medical Research project on molecular characterization of α-thalassemia by multiplex polymerase chain reaction. [10]

Thus, in clinically asymptomatic hemoglobin variants, in addition to routine hematological work-up, family studies and DNA mutation testing plays an important role in the correct diagnosis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
   References Top

1.
Trent RJ. Diagnosis of the haemoglobinopathies. Clin Biochem Rev 2006;27:27-38.  Back to cited text no. 1
    
2.
Angastiniotis M, Modell B. Global epidemiology of hemoglobin disorders. Ann N Y Acad Sci 1998;850:251-69.  Back to cited text no. 2
    
3.
Miyaji T, Suzuki H, Ohba Y, Shibata S. Hemoglobin agenogi (alpha 2 beta 2-90Lys), a slow-moving hemoglobin of a Japanese family resembling Hb-E. Clin Chim Acta 1966;14:624-9.  Back to cited text no. 3
    
4.
Földi J, Horányi M, Szelényi JG, Hollán SR, Kiss A, Spivak VA, et al. Hemoglobin agenogi in hungary. Hemoglobin 1988;12:395-8.  Back to cited text no. 4
    
5.
Corso D, Cognata B, Ciaccio C, Piazza T, Dibenedetto SP, Samperi P, et al. Hb Agenogi [beta 90(F6) Glu- Lys] and beta zero-thalassemia in a Sicilian family. Hemoglobin 1990;14:549-53.  Back to cited text no. 5
[PUBMED]    
6.
Joutovsky A, Hadzi-Nesic J, Nardi MA. HPLC retention time as a diagnostic tool for hemoglobin variants and hemoglobinopathies: A study of 60000 samples in a clinical diagnostic laboratory. Clin Chem 2004;50:1736-47.  Back to cited text no. 6
    
7.
Samperi P, Mancuso GR, Dibenedetto SP, Di Cataldo A, Ragusa R, Schilirò G. High performance liquid chromatography (HPLC): A simple method to quantify Hb C, O-Arab, Agenogi and F. Clin Lab Haematol 1991;13:169-75.  Back to cited text no. 7
    
8.
Paleari R, Mosca A, Maccaronio A, De Bellis G, Debernardi S, Lang F, et al. Hb Agenogi [beta 90(F6) Glu->Lys] identified by DNA analysis. Hemoglobin 1994;18:347-51.  Back to cited text no. 8
    
9.
Noguera NI, Cardozo MA, González FA, Benavente C, Milani AC, Villegas A. Hb Agenogi [P90(F6) Glu->Lys] in an Argentinean girl. Hemoglobin 2002;26:201-3.  Back to cited text no. 9
    
10.
Molecular Characterization of α-thalassemia by Multiplex PCR. Available from: icmr.nic.in/annual/2005-06/iih/haemotogenetics.pdf.  Back to cited text no. 10
    

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Correspondence Address:
Geetika Sharma
House Number 362, Sector 8, Panchkula - 134 109, Haryana
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0377-4929.174844

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