The premature boy, born by Cesarean section at 32 weeks of gestation, had a birthweight of 1850 g and Apgar scores of 6/1 and 9/5. Prenatal ultrasound was performed at 24 weeks of gestation and showed small bowel dilatation of the fetus and increased flow in the ascending aorta. The newborn had abdominal distension and had thin, fluid-like discharge from the rectum. Abdominal radiographs showed small bowel ileus (Fig. 1). On postnatal day 2, laparotomy was performed revealing a type 1 malrotation of the gut associated with obstructing Ladd’s Bands. On postnatal day 12, the newborn developed symptoms of late-onset sepsis caused by Klebsiella pneumoniae. Gastrointestinal bleeding, pulmonary hemorrhage and a small intracranial hemorrhage were also present. The patient had bilious emesis and failure to pass stool. Imaging studies showed dilated loops of the bowel; therefore, detorquation of a bowel loop and adhesiolysis were performed. After reoperation, he tolerated feeding and gained weight; however, repeated blood analyses indicated hyponatremia, hypochloremia, hypokalemia and metabolic alkalosis, necessitating prolonged oral electrolyte replacement therapy. Sweat test showed normal chloride concentrations and direct sequencing of the coding regions of the cystic fibrosis transmembrane conductance regulator (CFTR) gene revealed a single delta F508 mutation. The infant had frequent loose stools, sometimes 6–10 times per day. In the first year of life, he was frequently admitted to the hospital because of viral infections and dehydration, and needed electrolyte replacement in increasing amounts. A 24-h urine collection test showed low concentrations of sodium, potassium and chloride ions (9.7 mmol/l, 14.9 mmol/l and 6.6 mmol/l, respectively). Plasma renin activity (34.2 mg/ml/h) and aldosterone (51 mg/dl) levels were increased, suggesting secondary hyperaldosteronism. After exclusion of other possible causes, chloride loss in the feces was detected. Elevated chloride concentrations were detected in centrifuged feces samples (148 and 154 mmol/l; normal range is below 90 mmol/l) using standard chemistry analysis. Based on the high chloride levels in the stool, diagnosis of CCD was established.
To perform molecular genetic confirmation, peripheral blood samples were drawn from the affected patient and from his unaffected family members (n = 2), as well as from unrelated healthy controls (n = 50), and genomic DNA was isolated from the blood samples. The coding regions and the flanking introns of the SLC26A3 gene were amplified and sequenced. Direct sequencing of the investigated regions of the SLC26A3 gene revealed two heterozygous mutations: a novel thymine-base deletion (c.1295delT, p.Leu432Argfs*11, Fig. 2a) in exon 11 and a recurrent 3-base (TCA) duplication (c.2024_2026dupTCA, p.Ile675_Arg676insIle, Fig. 2b) in exon 18. After the disease-causing mutations were identified in the patient, the mutation status of the parents was determined (Fig. 3). The clinically unaffected parents carry the mutations in heterozygous form, and all unrelated healthy controls (n = 50) carry the wild type sequence.
After establishing the diagnosis, oral electrolyte supplementation was continued with 2,1 g of NaCl and 2,2 g of KCl a day, and proton pump-inhibitor therapy was also administered to inhibit gastric Cl− secretion. [6, 7] Since then no parenteral fluid replacement therapy was necessary, as electrolytes were in normal range and alkalosis did not recurred. 12 months after the conclusion of the genetic analysis, the patient has stools still 6–8 times a day, but successfully underwent toilet training. Currently at the age of 4, his weight is at 25 percentile (16 kg), his psychomotor development is appropriate for age, he attends nursery school.