Nuances in ATP7B Genetic Testing and Interpretation in India

Wilson disease is a monogenic (ATP7B gene) multisystemic disorder that affects copper metabolism. The hepatic variant is aggressive in Indian children. There are fallacies in the clinico-biochemical criteria for diagnosis, which result in dilemmas and delays in therapy. Genetic testing is near-confirmatory with the present next-generation sequencing. Exome sequencing is preferred by clinicians. The interpretation of the genetic results can be challenging. India has a high prevalence of endogamy and consanguinity, resulting in a high burden of the disease. Of the known 1300+ ATP7B variants, there are approximately 234 variants presently reported in India, and they differ widely in the four zones of the country. Variants p.C271X, p.G1061E, and p.G1101R are pan-Indian. The genotype-phenotype correlation is largely inconclusive, more so from India. Though genetic testing is recommended as the first line in the screening of first-degree relatives, the current practice in India is still by the clinico-biochemical approach. Asymptomatic homozygotes can be initiated early on therapy. Heterozygote carriers are important to identify as there are future implications in consanguineous unions and reproductive decisions. Population screening has not been explored in India and is the need of the hour, especially in ethno-linguistic zones. This review comprehensively discusses the utility and gaps of genetic testing for Wilson disease in India.