Persistent hyperkalemia in an otherwise healthy 4-month-old female: Answers
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CLINICAL QUIZ
Persistent hyperkalemia in an otherwise healthy 4-month-old female: Answers Grace Yu 1 & Faris Hashim 2 & Colleen Macmurdo 3 & Christian Hanna 4 Received: 3 April 2020 / Accepted: 6 April 2020 # IPNA 2020
Answers 1. Renal tubular acidosis (RTA) is a medical condition in which a defect in renal tubule function causes a non-gap metabolic acidosis. There are three types of RTA: type 1 (distal tubule hydrogen ion transport defect), type 2 (proximal tubule bicarbonate reabsorption defect), and type 4 (distal tubule defect due to aldosterone deficiency or resistance) [1]. While types 1 and 2 cause low to normal serum potassium levels, type 4 causes hyperkalemia. Differential diagnosis for type 4 RTA in children includes sequelae to critical illness, such as obstructive nephropathy, interstitial nephritis, diabetic nephropathy, primary adrenal insufficiency, or medications such as NSAIDs or ACE inhibitors [1, 2]. Pseudohypoaldosteronism (PHA) type I and type II are exceedingly rare genetic disorders that are caused by aldosterone resistance or reduced aldosterone production, respectively. When PHA type I occurs, patients often present with sodium wasting, hypovolemia, metabolic acidosis, and hyperkalemia in the neonatal period [3, 4]. PHA type II presents with hyperkalemia and hypertension in variable ages of
This refers to the article that can be found at https://doi.org/10.1007/ s00467-020-04572-w * Grace Yu [email protected] 1
Department of Pediatrics, Texas A&M Health Science Center, Baylor Scott & White McLane Children’s Medical Center, Temple, TX, USA
2
Division of Pediatric Nephrology, Baylor Scott & White McLane Children’s Medical Center, Temple, TX, USA
3
Division of Medical Genetics, Department of Internal Medicine, Baylor Scott &White Medical Center, Temple, TX, USA
4
Division of Pediatric Nephrology and Hypertension, Mayo Clinic, Rochester, MN, USA
patients, though most cases have been reported in adolescence or young adulthood [5, 6]. 2. The nature of her RTA type 4 was inconclusive at the time of hospital discharge. She had no history of failure to thrive and no significant medical history, so likelihood of RTA type 4 secondary to chronic conditions or medications was unlikely. To elucidate whether she may have possible pseudohypoaldosteronism, she was referred to genetics and a detailed evaluation was completed. Whole exome sequencing revealed a de novo heterozygous c.1376A>T (p.K459M) likely pathogenic variant in the Cullin 3 (CUL3) gene consistent with pseudohypoaldosteronism type II. This explained the low renin, hyperchloremia, severe hyperkalemia, and metabolic acidosis. Our patient exhibited normal blood pressure measurements during hospitalization and multiple outpatient nephrology follow-up visits, most likely due to her young age. Severe hypertension tends to develop later in life in the majority of cases [5, 7–10]. Interestingly, she had a second maternally inherited PRRT2 pathogenic variant linked to benign infantile familial seizures unrelated to her CUL3 pathogenic va
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