Congenital chloride diarrhea in patient with SLC26A2 mutation – analysis of the clinical phenotype and differential diagnosis

Introduction
To analyze the clinical features and SLC26A3 mutation of one patient in our hospital who had congenital loss of chlorine diarrhea (CLD), and to investigate the treatment of the disease and the prognosis.

Material and methods
By reviewing the literature, analyzing the clinical features and differential diagnosis and investigating the treatment and prognosis, the patient was diagnosed as CLD.

Results
Excessive accumulation of amniotic fluid was observed during pregnancy. The patient was born prematurely with normal body weight. The patient was a 4-month old boy admitted for anorexia, watery diarrhea, electrolyte disorders (hyponatremia, hypokalemia and hypochloremia) and metabolic alkalosis. The patient was also considered to be affected by Batter syndrome. After treating with spironolactone, indomethacin and potassium chloride sustained release tablet, the symptom of watery diarrhea was alleviated, the ingested amount of milk increased gradually and the amount of urine became normal; however, electrolyte imbalance persisted and the frequency of bowel movements remained high. Genetic analysis demonstrated that the patient had a SLC26A3 c.269_270dupAA homozygous mutation in exon 3, leading to a frameshift from 91st amino acid Gly and alteration of the SLC26A3 transmembrane protein sequence, thus resulting in a Cl–/HCO3– exchange barrier. The parents of the patient had normal phenotypes and were all heterozygous carriers of the mutation. Moreover, the patient was diagnosed as CLD. Sodium chloride and potassium chloride rather than spironolactone and indomenthacin were given to the patient to correct the dehydration, so the symptom of watery diarrhea alleviated and the blood gas and electrolyte levels returned to the normal range. In addition, the patients morale was good and the ingested amount of milk was moderate.

Conclusions
Persistent diarrhea and electrolyte disorder in pediatrics are easy to misdiagnose as CLD. Furthermore, it is difficult to identify Batter syndrome, Gitelman syndrome, renal tubular acidosis and CLD. Blood and stool electrolyte detection and SLC26A3 genetic tests are helpful for diagnosis, and sodium chloride and potassium chloride replacement therapy are critical for the patient prognosis.