Case Presentation: Pt was a FT 2wk old boy. At his 1st clinic appointment, he was 9% below birthweight. Mom reported appropriate feeding volume but he was sleeping throughout the day and needed to be woken for feeds. He was stooling 1-2 times per day with 4-5 wet diapers and no vomiting or fevers. At this appointment he was 15% below birthweight. On PE, he was thin with poor tone. His anterior fontanelle was sunken; his skin was ashen. The rest of the exam was WNL. He was admitted for continued weight loss and dehydration. Initial labs showed Na 126, K 8.2, chloride 88, HCO3 19, BUN/Cr of 20/0.38, and WBC 17.9. With his severe hyponatremia and hyperkalemia, there was concern for hypoaldosteronism so he received IV fluids and hydrocortisone. His aldosterone levels measured <1. An adrenal US was done to view hemorrhaging or abnormalities, a repeat newborn screen and 17-Hydroxyprogesterone to dx Congenital Adrenal Hyperplasia (CAH), and an ACTH stress test. Those tests came back normal except he had failed the ACTH stimulation test twice indicating a true primary adrenal insufficiency.The patient was stabilized and sent home on glucocorticoid, mineralocorticoid, and salt replacement therapy. On routine endocrine follow-up labs he was found to have significant transaminitis so he was readmitted to the hospital. Liver US was normal but his CPK was found to be 10,743. For the combination of hypoaldosteronism and elevated CPK (concerning for muscular dystrophy), he was referred to genetics who confirmed the diagnosis of a metabolic disorder called Chromosome Xp21 Deletion Syndrome, also known as Complex glycerol kinase deficiency.
Discussion: The initial concern for this child was continued weight loss at 2 wks. Initial testing was concerning for hypoaldosteronism, for which the most common reason in newborns is CAH, an autosomal recessive disorder that usually presents with vomiting (due to salt-wasting) and excess androgens in which affected females will have ambiguous genitalia but males usually have no obvious genital abnormalities. Another consideration is Pseudohypoaldosteronism, a salt wasting syndrome where the renal tubules are insensitive to mineralocorticoids. Other causes that were considered included adrenal hemorrhage, adrenal hypoplasia congenita, and hypovolemic hyponatremia. In this case, several disorders on the differential diagnosis were ruled out including CAH because 17-Hydroxyprogesterone was normal, Pseudohypoaldosteronism because aldosterone levels were undetectable, adrenal hemorrhage because the adrenal ultrasound was normal, and hypovolemic hyponatremia because symptoms did not resolve after rehydration.
The etiology of this patient’s hypoaldosteronism was not discovered until a CPK was measured and found to be extremely elevated. With a suspicion for Duchenne Muscular Dystrophy, genetics was consulted and helped make the diagnosis Complex Glycerol Kinase Deficiency. This is a rare disorder caused by a microdeletion of the GK gene and its neighboring genes: dystrophin (which causes Duchenne muscular dystrophy) and NR0B1, which causes adrenal hypoplasia congenita.
Conclusions: In children with suspected hypoaldosteronism, initial treatment is crucial in order to avoid adrenal crisis which can result in hypotension or shock as well as hyponatremia, metabolic acidosis, and hypoglycemia. As with this patient, immediate treatment with steroids and salt replacement will lead to better outcomes while trying to determine the definitive diagnosis.