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[Metabolic alkalosis and secondary hyperaldosteronism in cystic fibrosis (author's transl)]
Insights
Severe salt restriction in an infant with undiagnosed cystic fibrosis caused a dangerous metabolic imbalance due to excessive electrolyte loss through sweat, highlighting a key disease feature.
Area of Science:
- Pediatric Endocrinology
- Metabolic Disorders
- Genetics
Background:
- Infant formula with restricted sodium and chloride intake was administered to a child with an undiagnosed metabolic condition.
- Cystic Fibrosis (CF) is a genetic disorder affecting multiple organs, including the exocrine glands.
Observation:
- The child developed a life-threatening metabolic disturbance characterized by hypochloraemic alkalosis.
- Massive electrolyte loss occurred via sweat, despite low urinary electrolyte excretion due to aldosterone-induced reabsorption.
- Initial high plasma aldosterone levels normalized after salt supplementation.
Findings:
- The case illustrates a unique metabolic characteristic of cystic fibrosis: tubular electrolyte reabsorption coupled with impaired sweat gland reabsorption of sodium and chloride.
- Severe, prolonged salt restriction can lead to subpathological sweat electrolyte levels, potentially masking CF diagnosis.
Implications:
- This case underscores the critical importance of considering electrolyte imbalances in infants with unexplained metabolic disturbances.
- Diagnostic challenges in cystic fibrosis, particularly in neonates or infants with atypical presentations, are highlighted.
- Understanding the complex electrolyte handling in CF is crucial for appropriate clinical management and dietary interventions.
Abstract:
The prolonged use of a salt restricted infant formula (1.9 mEq Na/kg/day and 1,4 mEq C1/kg/day) in a child with undiagnosed cystic fibrosis led to a life threatening metabolic disturbance. The main features were hypochloraemic alkalosis due to massive loss of electrolytes in the sweat. Urinary electrolyte excretion, however, had been lowered to a minimum due to aldosteron induced reabsorption. Plasma aldosterone levels were initially high, but returned to normal after addition of salt to the feeds. Prior to admission a sweat test had been negative. The patient clearly demonstrates the unique metabolic feature of cystic fibrosis of the ability to retain electrolytes in the tubulus and at the same time the inability of the sweat glands to reabsorb sodium and chloride. Contrary to present experience severe prolonged salt restriction is believed to be able to diminish sweat electrolytes to subpathological values.