A rare cause of chronic hyponatremia in an infant: Questions

Excerpt

A seven-month-old female infant of Armenian origin presented with difficult feeding, vomiting, and inadequate weight gain starting from the first month of life. She was born at 38 weeks of gestation with a weight of 3.3 kg. She was fed breastmilk and formula. Vomiting started at 2 months of age; she refused breastmilk at 5 months. At 7 months of age, she was hospitalized because of a urinary tract infection, with mild hyponatremia (129 mmol/L) and hyperkalemia (5.7 mmol/L). Her family history was unremarkable except that her father had familial Mediterranean fever (FMF) and her mother had Hashimoto’s thyroiditis. On examination, she appeared mildly dehydrated. The body temperature was 36.0 °C, the pulse 120 beats/min, the blood pressure 95/50 mmHg (on the left lower leg), and the respiratory rate 24 breaths/min. Her body weight was 4.7 kg (− 4.05 standard deviation (SD)), and height was 61 cm (− 2.64 SD). Apart from a sacral dimple, physical examination was normal. …