Hyponatremia is a common electrolytes disorder in children. It can result from sodium chloride losses through GI, the kidneys, or in the sweat. Sodium chloride loss in the sweat can be caused by many different etiologies as cystic fibrosis, malnutrition, metabolic diseases, dermatological diseases and endocrine diseases. We are reporting a 6 months old boy, medically free, who had recurrent admissions to the PICU as a case of hyponatremic dehydration, with a sodium level of 117-116. Both of his parents are healthy, no consanguinity, with one healthy older brother. Investigations ruled out adrenal insufficiency, renal and GI losses of NACL, and pseudohypoaldosteronism. Additionally, a sweat chloride test was performed and came back positive with a result of 70 mEq/L, thus the diagnosis of cystic fibrosis was considered. However, he did not have frequent respiratory infections, no history of chronic cough or foul-smelling loose stools, and with no family history of cystic fibrosis. Due to the uncertainty of the diagnosis, WES was sent and came back positive for heterozygous pathogenic variant (c.601G>A) with a heterozygous risk factor (c.1210-11T>G) was identified in the CFTR gene, with the genetic diagnosis of AR cystic fibrosis, also a homozygous variant of uncertain significance was identified in the CA12 gene (c.668G>C) with the genetic diagnosis of AR isolated hyperchlorhidrosis is possible. Further genetic testing was done to the family to determine the pathogenicity.
|CFTR pathogenic variant (c.601G>A)||CFTR risk factor(c.1210-11T>G)||CA12 gene (c.668G>C)|
Based on the family sanger testing, we concluded that the patients presentation is due to hyperchlorhidrosis, as a result of Carbonic anhydrase XII (CA12) gene mutation. CA12 mutation causes an isolated chloride losses in the sweat. Furthermore, literature review showed that patients having mutation in CA12 can present with CF- like phenotype (FTT, Recurrent respiratory infections). However our patient did not develop any other cystic fibrosis manifestations.
21 Sep 2023 - 23 Sep 2023