[Salt fever]

Area of Science:

• Pediatrics
• Neonatology
• Endocrinology

Background:

• Hypernatraemia-induced fever in neonates, though recognized for a century, is infrequently considered in differential diagnoses.
• Neonatal hypernatraemia commonly results from insufficient breastfeeding, leading to significant weight loss proportional to serum sodium levels.

Purpose of the Study:

• To present a case study illustrating the differential diagnosis of neonatal hypernatraemia presenting with fever.
• To emphasize the importance of considering hypernatraemia and its underlying causes, including diabetes insipidus, in febrile neonates.

Main Methods:

• Case report of a four-day-old boy admitted with fever and hypernatraemia.
• Analysis of urine osmolality, specific gravity, and fractional sodium excretion to differentiate causes of hypernatraemia.
• Genetic testing to identify the underlying cause of diabetes insipidus.

Main Results:

• The patient presented with hypernatraemia (156 mmol/L) and hyposmolar urine (<100 mOsm/kg), suggesting diabetes insipidus.
• Genetic analysis revealed a frameshift variant in the AVPR2 gene, confirming X-linked nephrogenic diabetes insipidus.
• Treatment with hypothiazide and indomethacin effectively managed polyuria and prevented recurrent hypernatraemia.

Conclusions:

• Fever in neonates warrants consideration of hypernatraemia, which can be induced by dehydration or salt toxicity.
• The coexistence of hypernatraemia and hyposmolar urine is a key indicator for suspecting diabetes insipidus.
• Early diagnosis and appropriate management, including fluid balance and specific treatments like thiazides and NSAIDs, are crucial for resolving hypernatraemia and preventing recurrence.