Screening for the Most Common Mutations of CFTR Gene among Egyptian Children with Difficult-to-Treat Asthma

Abstract

Cystic fibrosis (CF) is panethnic autosomal recessive disease that affects the exocrine glands of pancreas, lungs, and intestine. It is often misdiagnosed in developing countries as difficult-to-treat asthma. We enrolled 150 Egyptian families with one or more probands who were complaining of difficult-to-treat asthma, and 112 cases were studied extensively through history taking including pedigree construction and clinical examination. In addition, spirometry and computed tomography of the chest were done in selected cases. All cases were subjected to quantitative sweat chloride test and molecular screening for the three most common mutations of cystic fibrosis transconductance regulator (CFTR) gene (ΔF508, G542X, W1282X) using amplification refractory mutation system (ARMS) technique. Probands of difficult-to-treat asthma comprised 66 males and 46 females; their age range was 1 to 14 years. Sixty-one probands (54.5%) were carriers of one or more of the studied mutations (36 cases and 25 carriers). Six carriers of single mutations had mild respiratory symptoms and negative sweat test. The most common allele was ΔF508, 60 alleles in 56 individuals (4 were homozygous ΔF508/ΔF508) followed by W1282X in 25 individuals and G542X in 12 individuals. Allele W1282X had an increased risk of recurrent chest infection and bronchiectasis. Moreover, cases with two mutations had more severe symptoms compared with those with a single mutation. CFTR mutations and CF-related syndromes are not rare as thought in Egypt, especially among the high-risk difficult-to-treat asthma. The readily available ARMS technique is recommended for ΔF508 and/or W1282X screening on priority basis among these children.

The burden of cystic fibrosis in North Africa

“…Six carriers of single variants in this research had minor respiratory symptoms and negative sweat tests. Out of the 112 probands of difficult-to-treat asthma, 61 individuals carried one or more of the studied three variants (54.5%): 36 individuals had two variants (considered CF after sweat chloride testing for confirmation) and 25 individuals carried single variants ( Al-Haggar et al, 2020 ) ( Figures 3A,B ).…”