Whole exome sequencing: Unlocking the molecular diagnostic odyssey in Pakhtun ethnic group of Pakistani population.

The Pakhtuns are 40.86 million people, accounting for 16.9 % of the Pakistani population, and primarily reside in the Khyber Pakhtunkhwa province. The Pakistani population in general, and the Pakhtun belt in particular, is divided into small, isolated tribes where inbreeding is very high (>55 %). This leads to high frequency of rare genetic diseases, making "Rare" conditions relatively common in this population. Due to the high frequency and overlapping phenotypes of affected individuals, molecular diagnostics are often difficult and time consuming. We investigated 1374 individuals from 272 families, including those with skin disorders (n = 52), vision disorders (n = 50), deafness (n = 26), neurological disorders (n = 102), and skeletal disorders (n = 42). Whole exome sequencing of the index patient was performed, and causative variant prioritization was carried out using an autosomal recessive model, following the ACMG 2015 guidelines and confirming segregation with the disease phenotypes via Sanger sequencing. Successfully resolved cases comprised of 69.5 %, of which 70.8 % (n = 136) had homozygous variants, while 6.3 % (n = 12) had compound heterozygous variations. This is a comprehensive study of the Pakhtun ethnic group, addressing the most common genetic disorders within this population. It has implications for the policy already approved by the local government to conduct pre-marital testing, aiming to reduce the disease burden in future generations. However, the study had limitations: we could not perform whole genome sequencing for the unresolved 30.5 % families (n = 83), and the sample size was not representative of the entire 40.86 million population. Nonetheless, the alarming incidence of rare diseases in this population supports the assertion that "rare" conditions are indeed common here.