The 8-month-old patient was hospitalized after a few days of apathy and feeding difficulty with moderate exsiccation. Severe hypokalemia, hyponatremia, hypochloremia associated with alcalosis were found, which were accompanied by the decreased urinary electrolytes and elevated serum renin and aldosteron, therefore the condition corresponded to a pseudo-Bartter syndrome. The diagnosis of cystic fibrosis was arisen, which was established by the elevated sweat cloride levels. Sequencing of the 27 exons of the cystic transmembrane regulator gene two rare mutations were detected in compound heterozygous form: in the exon 10 a C1529G transversion, whereas in the exon 20 a G3978A transition was verified, both of them result in development of premature stopcodons (S466X and W1282X, respectively). Carriage of first mutation could be found in the asymptomatic mother, while the other one was identified in the father. In the proband and in the mother a G3341A mutation was also detected in exon 17, which causes an R1070Q amino acid change. However, this likely cannot associate with pathology since the existing premature stopcodon on the same allele does not allow synthesis of protein. These mutations have been described in combination with ΔF508 mutation, however, their simultaneous presence in the same subject has not been reported. During the one and half year follow-up the clinical picture appeared benign.
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