Congenital chloride-losing diarrhea in a Mexican child with the novel homozygous SLC26A3 mutation G393W

Diet management in congenital diarrheas and enteropathies - general concepts and disease-specific approach, a narrative review

Congenital diarrheas and enteropathies (CODE) are a group of rare, heterogenous, monogenic disorders that lead to chronic diarrhea in infancy. Definitive treatment is rarely available, and supportive treatment is the mainstay. Nutritional management in the form of either specialized formulas, restrictive diet, or parenteral nutrition support in CODE with poor enteral tolerance is the cornerstone of CODE treatment and long-term growth. The evidence to support the use of specific diet regimens and nutritional approaches in most CODE disorders is limited due to the rarity of these diseases and the scant published clinical experience. The goal of this review was to create a comprehensive guide for nutritional management in CODE, based on the currently available literature, disease mechanism, and the PediCODE group experience. Enteral diet management in CODE can be divided into 3 distinct conceptual frameworks: nutrient elimination, nutrient supplementation, and generalized nutrient restriction. Response to nutrient elimination or supplementation can lead to resolution or significant improvement in the chronic diarrhea of CODE and resumption of normal growth. This pattern can be seen in CODE due to carbohydrate malabsorption, defects in fat absorption, and occasionally in electrolyte transport defects. In contrast, general diet restriction is mainly supportive. However, occasionally it allows parenteral nutrition weaning or reduction over time, mainly in enteroendocrine defects and rarely in epithelial trafficking and polarity defects. Further research is required to better elucidate the role of diet in the treatment of CODE and the appropriate diet management for each disease.

Congenital chloride diarrhea clinical features and management: a systematic review

INTRODUCTION

Congenital chloride diarrhea (CLD) is a rare autosomal recessive disorder characterized by watery diarrhea with a high level of fecal Cl^-, metabolic alkalosis, and electrolyte alterations. Several intestinal and extraintestinal complications and even death can occur. An optimal knowledge of the clinical features and best therapeutic strategies is mandatory for an effective management.

METHODS

Articles published between 1 January 1965 and 31 December 2019, reported in PUBMED and EMBASE, were evaluated for a systematic review analyzing four categories: anamnestic features, clinical features, management, and follow-up strategies.

RESULTS

Fifty-seven papers reporting information on 193 CLD patients were included. The most common anamnestic features were positive family anamnesis for chronic diarrhea (44.4%), consanguinity (75%), polyhydramnios (98.3%), preterm delivery (78.6%), and failure to pass meconium (60.7%). Mean age at diarrhea onset was 6.63 days. Median diagnostic delay was 60 days. Prenatal diagnosis, based on molecular analysis, was described in 40/172 (23.3%). All patients received NaCl/KCl-substitutive therapy. An improvement of diarrhea during adulthood was reported in 91.3% of cases. Failure to thrive (21.6%) and chronic kidney disease (17.7%) were the most common complications.

CONCLUSIONS

This analysis of a large population suggests the necessity of better strategies for the management of CLD. A close follow-up and a multidisciplinary approach is mandatory to manage this condition characterized by heterogeneous and multisystemic complications.

IMPACT

In this systematic review, we describe data regarding anamnestic features, clinical features, management, and follow-up of CLD patients obtained from the largest population of patients ever described to date. The results of our investigation could provide useful insights for the diagnostic approach and the management of this condition.

SLC26A3 mutation in Turkish neonate and her sibling with congenital chloride diarrhea

Congenital chloride diarrhea is a rare cause of severe infantile diarrhea with excessive chloride excretion. Mutations in the SLC26A3 gene cause congenital chloride diarrhea. It generally becomes apparent in the neonatal period and is characterized by electrolyte imbalances, metabolic alkalosis, and failure to thrive. The diagnosis of congenital chloride diarrhea is based on detecting excessive chloride in the stool (90 mmol/L). We report a Turkish neonate with congenital chloride diarrhea whose sibling had the same disease. The newborn was born by cesarean delivery. Diarrhea, vomiting, and weight loss started soon after birth. She was diagnosed as having congenital chloride diarrhea based on its typical clinical signs and a high concentration of stool chloride and was confirmed by genetic analysis. She was treated by means of salt supplementations and lansoprazole. Family history may play an important role in the early diagnosis because the disease is inherited autosomal recessively.

Extracellular Cl(-) regulates human SO4 (2-)/anion exchanger SLC26A1 by altering pH sensitivity of anion transport

Genetic deficiency of the SLC26A1 anion exchanger in mice is known to be associated with hyposulfatemia and hyperoxaluria with nephrolithiasis, but many aspects of human SLC26A1 function remain to be explored. We report here the functional characterization of human SLC26A1, a 4,4'-diisothiocyanato-2,2'-stilbenedisulfonic acid (DIDS)-sensitive, electroneutral sodium-independent anion exchanger transporting sulfate, oxalate, bicarbonate, thiosulfate, and (with divergent properties) chloride. Human SLC26A1-mediated anion exchange differs from that of its rodent orthologs in its stimulation by alkaline pHo and inhibition by acidic pHo but not pHi and in its failure to transport glyoxylate. SLC26A1-mediated transport of sulfate and oxalate is highly dependent on allosteric activation by extracellular chloride or non-substrate anions. Extracellular chloride stimulates apparent V max of human SLC26A1-mediated sulfate uptake by conferring a 2-log decrease in sensitivity to inhibition by extracellular protons, without changing transporter affinity for extracellular sulfate. In contrast to SLC26A1-mediated sulfate transport, SLC26A1-associated chloride transport is activated by acid pHo, shows reduced sensitivity to DIDS, and exhibits cation dependence of its DIDS-insensitive component. Human SLC26A1 resembles SLC26 paralogs in its inhibition by phorbol ester activation of protein kinase C (PKC), which differs in its undiminished polypeptide abundance at or near the oocyte surface. Mutation of SLC26A1 residues corresponding to candidate anion binding site-associated residues in avian SLC26A5/prestin altered anion transport in patterns resembling those of prestin. However, rare SLC26A1 polymorphic variants from a patient with renal Fanconi Syndrome and from a patient with nephrolithiasis/calcinosis exhibited no loss-of-function phenotypes consistent with disease pathogenesis.