Point of Care Exome Sequencing Reveals Allelic and Phenotypic Heterogeneity Underlying Mendelian disease in Qatar

Khalid A. Fakhro, Amal Robay, Juan L. Rodrigues-Flores, Jason G. Mezey, Alya A. Al-Shakaki, Omar Chidiac, Dora Stadler, Joel A. Malek, Abu Bakr Imam, Arwa Sheikh, Asmaa Azzam, Ibrahim Janahi, Izzat Khanjar, Kamal Osman, Maen Abu Ziki, Mohamed Adnan Mahmah, Mohamed Selim, Nuha Numeiri, Rehab Ali, Shenela LakhaniFizza Butt, Tawfeg Ben Omran, Ronald G. Crystal

Research output: Contribution to journalArticle


The effectiveness of next generation sequencing at solving genetic disease has motivated the rapid adoption of this technology into clinical practice around the world. In this study, we use whole exome sequencing (WES) to assess 48 patients with Mendelian disease from 30 serial families as part of the "Qatar Mendelian Disease pilot program" - a coordinated multi-center effort to build capacity and clinical expertise in genetic medicine in Qatar. By enrolling whole families (parents plus available siblings), we demonstrate significantly improved discriminatory power for candidate variant identification over trios for both de novo and recessive inheritance patterns. For the same index cases, we further demonstrate that even in the absence of families, variant prioritization is improved up to 8-fold when a modest set of population-matched controls is used vs large public databases, stressing the poor representation of Middle Eastern alleles in presently available databases. Our in-house pipeline identified candidate disease variants in 27 of 30 families (90%), 23 of which (85%) harbor novel pathogenic variants in known disease genes, pointing to significant allelic heterogeneity and founder mutations underlying Mendelian disease in the Middle East. For 6 of these families, the clinical presentation was only partially explained by the candidate gene, suggesting phenotypic expansion of known syndromes. Our pilot study demonstrates the utility of WES for Middle Eastern populations, the dramatic improvement in variant prioritization conferred by enrolling population-matched controls and/or enrolling additional unaffected siblings at the point-of-care, and 25 novel disease-causing alleles, relevant to newborn and premarital screening panels in regional populations.

Original languageEnglish
Pages (from-to)3970-3981
Number of pages12
JournalHuman molecular genetics
Issue number23
Publication statusPublished - 1 Dec 2019


ASJC Scopus subject areas

  • Molecular Biology
  • Genetics
  • Genetics(clinical)

Cite this

Fakhro, K. A., Robay, A., Rodrigues-Flores, J. L., Mezey, J. G., Al-Shakaki, A. A., Chidiac, O., Stadler, D., Malek, J. A., Imam, A. B., Sheikh, A., Azzam, A., Janahi, I., Khanjar, I., Osman, K., Ziki, M. A., Mahmah, M. A., Selim, M., Numeiri, N., Ali, R., ... Crystal, R. G. (2019). Point of Care Exome Sequencing Reveals Allelic and Phenotypic Heterogeneity Underlying Mendelian disease in Qatar. Human molecular genetics, 28(23), 3970-3981. https://doi.org/10.1093/hmg/ddz134