Unearthing the genotype-inhibitor phenotype association in severe haemophilia A: A north Indian cohort study

INTRODUCTION

Various risk factors for inhibitor development in haemophilia A (HA) have been described but Indian data remains scanty.

AIM

We aimed to evaluate the genetic changes in Indian HA-patients that are associated with the development of inhibitors.

METHODS

All HA-patients with inhibitors who availed coagulation-laboratory services from January-2015 till December-2021 and had their samples preserved for DNA extraction were included in this study. An equal number of severity-matched HA patients without inhibitors were also included as controls. Intron 22 and intron 1 inversions in Factor VIII gene were identified using inverse-shifting-PCR. Inversion-negative patients were further assessed by targeted NGS, MLPA.

RESULTS

Thirty HA-patients with inhibitors were identified. All had severe-HA. Thirty severe-HA-patients without inhibitors were also included as controls. Intron 22 inversion (63.3%) and large deletions (15%) were the commonest variants identified. There was no difference in genetic variants in patients with low and high titre inhibitors. A3, A2 and C2 were the most common domains involved in inversion-negative patients with inhibitors. However, there was no significant difference in domain involvement among inversion-negative patients with and without inhibitors. Seven novel-variants were identified, including three large deletions, one large duplication and two nonsense variants in inhibitor-positive patients, and one frameshift variant in inhibitor-negative patient. After adjusting for clinical risk-factors, large deletions were independently associated with the presence of inhibitors [aOR:6.1 (1.41-56.3)].

CONCLUSION

Intron 22 inversions are the commonest variant in Indian patients with severe-HA. Large deletions predispose to inhibitor development independent of clinical risk factors.

Prenatal diagnosis for hemophilia A (intron 22 inversion) reveals a rare association with Klinefelter syndrome with diagnostic difficulties in molecular interpretation

Hemophilia A is an X-linked recessive disorder caused by genetic abnormalities in the F8 . Klinefelter syndrome is sex chromosome aneuploidy caused by nondisjunction during meiosis in the germ cells or mitotic cell divisions in the early embryonic cells. We here report an intriguing case of a prenatal diagnosis where a rare association of hemophilia A and Klinefelter syndrome was found in a fetus. This case highlights the diagnostic difficulty where the inverse-PCR for intron 22 inversion defect leading to hemophilia A did not amplify. Indirect molecular testing was done using multiallelic extragenic variable number tandem repeat (VNTR) DXS52 (St14) and polymorphic markers. The interpretation was further complicated by the presence of Klinefelter syndrome. This case highlights the challenges faced when such rare combinations are found during prenatal diagnosis.

Erythropoietin and ferritin response in native highlanders aged 4-19 years from the Leh-Ladakh region of India

The pivotal role of erythropoietin (EPO) in hypoxic adaptation has led to various studies assessing the EPO and ferritin response in native highlanders from Andes and Tibet. We assessed the relationship between EPO, haemoglobin and ferritin in 335 native highlanders (172 boys and 163 girls, aged 4 to 19 years) from Leh-Ladakh, India, who had no history of travel to lowland areas. Complete blood counts, serum EPO and ferritin levels were measured. We stratified study subjects based on age, gender, pubertal status and analysed the EPO and ferritin levels between the stratified groups respectively. The mean EPO level in boys was lower than girls. The mean ferritin level in boys was significantly higher (P = 0·013) than in girls. There was no significant variation in the EPO and ferritin levels amongst the various age groups in our study. Near normal EPO levels since childhood with a negative correlation with haemoglobin is suggestive of a robust adaptive mechanism to high altitude from the early years of life. Low ferritin levels are indicative of decreased iron stores in these native highlanders.

Thrombophilic risk factors are laterally associated with Apolipoprotein E gene polymorphisms in deep vein thrombosis patients: An Indian study

INTRODUCTION

Deep vein thrombosis is a multifactorial disease with many acquired and genetic risk factors. Polymorphism in the APOE gene is an upcoming potential pathogenic factor whose role is unclear in deep vein thrombosis.

METHODS

An equal number of deep vein thrombosis cases and controls (N = 100, each) were investigated for APOE gene polymorphisms along with known acquired and hereditable thrombophilic risk factors. APOE genotyping was done by polymerase chain reaction.

RESULTS

The ε3/ε4 and ε2/ε3 APOE genotypes were commoner in deep vein thrombosis cases than controls but not statistically significant ( ε3/ε4 → 18% versus 11%, OR = 1.776, CI = 0.792-3.984, p = 0.16; ε2/ε3 →10% versus 9%, OR = 1.123, CI = 0.436-2.895, p = 0.809). However, the following risk factors were found to be laterally associated with APOE genotypes in cases of deep vein thrombosis: pregnancy with ε2/ε3 genotype positivity (N = 29; p = 0.019), recurrent pregnancy loss with ε3/ε3 genotype (N = 29; p = 0.016), normal antithrombin levels with ε3/ε3 genotype (N = 62; p = 0.03) and non-O blood group with ε3/ε4 genotype (N = 100; p = 0.023).

CONCLUSION

APOE genotypes have shown only a modest association with deep vein thrombosis and were not statistically significant. A lateral association of these genotypes with thrombophilic risk factors was observed which may be investigated further for the possible pathogenetic mechanisms and their therapeutic implications.