A Case of Cystic Fibrosis With a Rare Mutation (3849 + 10 kbC > T) and Normal Sweat Chloride Levels

Cystic Fibrosis is an autosomal recessive disorder, which is caused by mutations in CFTR gene on chromosome 7q31.2. The prevalence of CF is approximately 1 in 2500 in Caucasians. In other populations, it has been seen less frequently. Characteristic features include chronic pulmonary disease, pancreatic exocrine insuf-ficiency and secretory systems such as gastro-intestinal and reproductive system function abnormalities. Current guidelines for the diagnosis of CF suggest that a patient must present one or more characteristic phe-notypic features or a positive newborn screening test result and a positive sweat test or two CF-causing mutations (1). A screening for CFTR mutations is essential if the sweat test is not conclusive. Here we present a female who was diagnosed with CF at age 1-year with a rare homozygous mutation 3849 + 10 kb C > T and normal sweat chloride concentrations. The proband was a 1-year-old female born to consanguineous parents (Figure 1). She was born at 38 weeks of gestation with a birth weight of 3610 g, birth height of 51 cm and birth head circumference of 37 cm. She was admitted to the hospital at 2 months of age because of respiratory distress syndrome. Her weight was 4700 g (50th percentile), height: 56 cm (75th percentile) and head circumference was 37.5 cm (25th-50th percentile). Intercostal and subcostal re-tractions were seen and bilateral crackles were heard at the lung in physical examination. Hemoglobin 10.3 g/ dL (N: 9-14 g/dL), white blood cells 6670/ µL (N: 6000-17500), platelets 577000/µL (N: 150,000-450,000), C-re-active protein 21 mg/dL (N: 0-5 mg/dL) and normal blood biochemistry and liver function tests were detected in laboratory investigations. Her chest roentgenogram demonstrated bilateral pulmonary infiltrations and atelectasis (Figure 2). Computerized-tomography (CT) showed fibro-atelectatic bands in right medial lobe and left lower lobe. Echocardiography was normal. Steator-rhoea was detected a few times. Her sweat chloride concentrations were 40 mmol/L (evaluated twice) (N: ≤ 40 mmol/L). CF was suspected due to her clinical features and laboratory findings. Molecular analysis revealed a homozygous mutation 3849 + 10 kb C > T in CFTR. The patient's mother and father were heterozygous for this mutation (Figure 1) and there were no clinical findings. CF is a complex multi-system disorder. The pathological basis of this disorder is based on mutations in the CFTR gene which encodes the cystic fibrosis transmembrane conductance regulator, a membrane chloride channel located in the apical membrane of secretory epithelia. CF has …