Cystic fibrosis: Defining a disease under-diagnosed in Pakistan

Objective Cystic fibrosis is frequently missed in the Pakistani population due to lack of appropriate diagnostic tools. Thus our aim was to define unknown disease-causing mutations to help create suitable diagnostic tests and improve understanding of what appears to be an aggressive and under-diagnosed disease in this population. Methods Patients with elevated sweat chloride values and clinically suspected CF were recruited from Aga Khan University, Pakistan. Mutations DF508, S549R, S549N, Y569D, 296 + 12(T>C), G553X, G551D and G551X were screened for by allele specific polymerase chain reactions. CFTR exons 10, 11 and 12 were sequenced by direct DNA sequencing. Results Of 150 patients tested by PCR, 26 (17.3%) were positive for δF508. One patient was a F508/S549N compound heterozygote. Eighty-three of 87 patients sequenced for mutations in exon 10 were normal; 42/43 for exon 11 and 29 for exon 12 were normal. Conclusion This first step in defining mutations involved in Pakistani CF suggests that δF508 is uncommon and S549 was the only additional mutation identified in CFTR exons 10, 11 and 12. Identification of the remaining mutations and their frequency is required to design appropriate tests and improve understanding and management of the disease.