Indian Journal of Pathology and Microbiology

CASE REPORT
Year
: 2019  |  Volume : 62  |  Issue : 2  |  Page : 323--325

Diagnostic challenges posed by a rare alpha globin chain variant Hb Fontainebleau in a pregnant female and its potential effects in her children in view of multiple globin gene defects in her husband


Kainaz Sidhwa1, Manisha Ramani Daruwalla1, Ravikiran Pawar1, Anita Nadkarni2, Priya Hariharan2, Pallavi Mehta2, Amar Das Gupta1,  
1 Department of Hematology, Central Reference Laboratory, SRL Limited, Mumbai, Maharashtra, India
2 Department of Hematogenetics, National Institute of Immunohematology, Mumbai, Maharashtra, India

Correspondence Address:
Amar Das Gupta
Section of Hematology, SRL Limited, Prime Square Building, Gaiwadi Industrial Estate, S. V. Road, Goregaon West, Mumbai - 400 062, Maharashtra
India

Abstract

Alpha globin chain variants per se do not cause severe morbidity and mortality but can modify – usually ameliorate – the clinical manifestations of beta globin chain variants when co-inherited with the latter. They also pose challenges in interpretation of high-performance liquid chromatography histograms and require molecular analysis for proper characterization. Hemoglobin (Hb) Fontainebleau is a rare alpha globin chain variant [alpha 21(B2) Ala→Pro], of which only three families have been reported from India in the past. Here, we describe a case of Hb fontainebleau detected in heterozygous condition in a 19-year-old primigravida. Her husband was found to have a double heterozygous state for HbQ India and beta-thalassemia trait. This opens up the possibility of multiple combinations of hemoglobinopathies in the offspring.



How to cite this article:
Sidhwa K, Daruwalla MR, Pawar R, Nadkarni A, Hariharan P, Mehta P, Gupta AD. Diagnostic challenges posed by a rare alpha globin chain variant Hb Fontainebleau in a pregnant female and its potential effects in her children in view of multiple globin gene defects in her husband.Indian J Pathol Microbiol 2019;62:323-325


How to cite this URL:
Sidhwa K, Daruwalla MR, Pawar R, Nadkarni A, Hariharan P, Mehta P, Gupta AD. Diagnostic challenges posed by a rare alpha globin chain variant Hb Fontainebleau in a pregnant female and its potential effects in her children in view of multiple globin gene defects in her husband. Indian J Pathol Microbiol [serial online] 2019 [cited 2020 Jan 23 ];62:323-325
Available from: http://www.ijpmonline.org/text.asp?2019/62/2/323/255807


Full Text



 Introduction



Until date, over 200 alpha chain variants have been identified.[1] Most of these were picked up during hemoglobinopathy screening programs. Studies involving the spectrum and frequency of alpha globin chain variants in India are very few.[2] The clinical importance of alpha chain variants lies in the moderation they cause in the phenotype and severity of clinical manifestations of other globin chain disorders, especially beta globin chain defects, when co-inherited with the latter. This is very well demonstrated by the first report of hemoglobin (Hb) Fontainebleau from India, wherein a woman and her baby were found to have Hb Fontainebleau, a rare alpha globin chain variant,[3] in a compound heterozygous state with HbS.[4]

Here, we report a case of Hb Fontainebleau [alpha 21(B2) Ala→Pro] detected in heterozygous condition in a primigravida as a part of her antenatal screening. This would be the fourth case of Hb Fontainebleau reported from the Indian subcontinent.

 Case History



A 19-year-old Sikh female, born of nonconsanguineous marriage, underwent Hb variant analysis as a part of her routine antenatal screening. She had no previous history of anemia or blood transfusions. Laboratory investigations revealed Hb 11.6 g/dl with red cell count 4.82 × 109/l, total leucocyte count 10.2 × 109/l with normal differential count, and platelet count 219 × 109/l. Red blood cell indices revealed a mildly reduced mean corpuscular volume (MCV) (77.8 fl), mean corpuscular hemoglobin (MCH) (24.2 pg), and MCH concentration (MCHC) (31.1 g/dl). Red cell distribution width was 15.7%. Hb variant analysis carried out by high-performance liquid chromatography (HPLC) on the variant II Hb testing system (Bio Rad Laboratories, Hercules, CA, USA) revealed a small abnormal Hb peak (12.5%) with a retention time of 2.92 min, appearing as a hump following and close to the HbA peak [Figure 1]a. The other Hbs seen in HPLC were HbA (83.6%), HbA2 (1.7%), and Hb F (0.3%).{Figure 1}

The proband's father revealed the presence of a similar abnormal Hb peak (12.6%) with a retention time of 2.93 min on HPLC analysis. His HbA2 was 2.5% and HbF was 0.2%. His hemogram was normal.

Molecular characterization of the abnormal Hb in the proband's father by reverse DNA sequencing (Applied Biosystems, Foster City, USA) showed the presence of a heterozygous G>C substitution at codon 21 (alpha 2 globin gene) [Figure 1]d, leading to the substitution of alanine by proline at the beginning of the beta helix corresponding to Hb Fontainebleau.

Hb variant analysis of the index case's husband showed an elevated Hb A2 of 5.7% along with a sharp abnormal Hb peak (8.3%) with a retention time of 4.67 min, followed immediately by a very small Hb peak [Figure 1]b. This suggested a compound heterozygous state for HbQ India and beta-thalassemia.

The proband's baby could be investigated at the age of 7 months after much persuasion of the parents. She had microcytic hypochromic anemia (Hb 8.5 g/dl; MCV 57.8 fl; MCH 16.9 pg; and MCHC 29.3 g/dl) and was compound heterozygous for HbQ India (9.2%; retention time: 4.65 min) and beta-thalassemia (HbA2: 6.3%) [Figure 1]c like her father. The HbA2 peak in both the father and daughter was asymmetric and showed a small hump in the descending limb of the peak. The baby also had mildly elevated HbF (8.5%), which was consistent with her age.

 Discussion



Hb Fontainebleau is a rare alpha chain variant that elutes out as a hump close to the descending limb of the HbA peak in HPLC and can pose considerable diagnostic difficulty to those unfamiliar with this entity.[3],[4] However, Hb Fontainebleau has not been found to be associated with any hematological abnormality in earlier reports from different parts of the world, including India.[3],[4],[5],[6],[7] Our index patient and her father, both of whom had Hb Fontainebleau, did not show any clinical or hematological finding related to the presence of this alpha chain variant. The mildly reduced Hb value and microcytic red cell indices in her could have resulted from pregnancy associated changes and a concomitant iron deficiency. In addition, her HbA2 level was low as has been previously reported in some other cases.[5]

Interestingly, the compound heterozygosity for beta thalassemia trait and another alpha globin chain variant, HbQ India in the proband's husband raised the following possibilities for the genotypes of the unborn baby when we first examined the couple,

Compound heterozygosity for Hb Fontainebleau and HbQ IndiaHeterozygous state for only Hb Fontainebleau or HbQ IndiaCompound heterozygosity for Hb Fontainebleau and beta thalassemia traitCompound heterozygosity for HbQ India and beta thalassemia traitCo-inheritance of all the three abnormalities, namely, Hb Fontainebleau, HbQ India, and beta thalassemia trait.

The baby, however, was found to have inherited HbQ India and beta thalassemia trait from her father and no Hb Fontainebleau from the mother [Figure 1]c. That the sharp abnormal Hb peaks in HbS window (retention time 4.65–4.67 min) in the baby and her father were indeed HbQ India was supported by (i) the small hump and a protracted slope of the descending limb of the HbA2 peak in HPLC as compared to the mother's symmetric HbA2 peak, caused by a variant HbA2 resulting from combination of the abnormal alpha chain of HbQ India with the normal delta chain; (ii) very small S-window peaks appearing as slight irregularities [Figure 1]b and [Figure 1]c; and (iii) the small post-HbQ peak has been observed in HPLC of this abnormal Hb and other alpha chain variants in published reports.[8],[9] As previously reported in compound heterozygotes of HbQ India and beta thalassemia trait, HbQ levels in the husband and the daughter of the index case (8.3% and 9.2%, respectively) were lower than those observed in simple hererozygotes of HbQ India (mean level 20%).[8],[10] This could reflect an attempt by red cells to preferentially synthesize HbA at the cost of HbQ when beta thalassemia is co-inherited.[10] The baby's anemia and microcytic hypochromic red cell indices could have resulted from the interplay of coexistent iron deficiency - not uncommon at her age – and beta thalassemia trait because HbQ India is not associated with microcytosis.

The parents of the baby have been counseled about the various genotypic and phenotypic possibilities (listed above) of their future offspring and the clinical implications thereof.

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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