Abstract: PO1322
Insight into the Pathophysiology of Hearing Loss and Renal Tubular Dysfunction Through Genetic Testing
Session Information
- Genetic Diseases of the Kidneys: Non-Cystic - I
November 04, 2021 | Location: On-Demand, Virtual Only
Abstract Time: 10:00 AM - 12:00 PM
Category: Genetic Diseases of the Kidneys
- 1002 Genetic Diseases of the Kidneys: Non-Cystic
Authors
- West, Dylan H., Baton Rouge General Medical Center - Bluebonnet, Baton Rouge, Louisiana, United States
- Samuel, Jones, Baton Rouge General Medical Center - Bluebonnet, Baton Rouge, Louisiana, United States
Introduction
In this case report, we present a case of Type 3b Bartter’s Syndrome associated with sensorineural hearing loss.
Case Description
A 69 year old caucasian female with a history of hypertension and osteoporosis presented to the emergency department with a worsening dry cough, altered mental status, and paresthesias. Physical examination was positive for Chvostek's sign and hearing loss bilaterally. Laboratory analysis was significant hypolcalcemia, hypokalemia, and hypomagnesemia. EKG on presentation displayed significant QT prolongation (QTc of 482 ms). The patient was treated for symptomatic hypocalcemia and initiated on calcium, potassium, and magnesium supplementation. 24 hour urine collection yielded: potassium and magnesium wasting and normal range calciuria. Parathyroid hormone was found to be inappropriately low in the setting of severe hypocalcemia but attributed to hypomagnesemia. Bartter's vs. Gittleman's was suspected, although profound hypomagnesemia suggested the latter.
Renasight, a kidney gene panel employing next generation genome sequencing revealed a heterozygous variant in the basal chloride channel (CLCNKB), associated with Bartter’s Syndrome Type 3/4B. This channel is found in the stria vascularis and can lead to sensorineural deafness. Hypoparathyroidism persisted in spite of adequate Magnesium, Vit D levels suggestive of primary hypoparathyroidism of autoimmune etiology.
Discussion
The positivity of CLCKNB heterozygous mutation suggested Bartter's Type 3/4B and this explained hearing loss and aided in the final diagnosis.
Individuals who express both type A and B mutations present in infancy or antenatally. In a series of 115 patients w/ type B gene mutation, 26% had a Gitelman-like syndrome which includes late onset of age (1).
Our case illustrated the utility of genetic testing in mixed electrolyte wasting presentations. Interestingly, the patient has persistent hypoparathyroidsism for which no genetic basis was identified such as the calcium sensing receptor mutation.
Renal Studies
| Magnesium | Potassium | Calcium | Chlroide | Creatinine | PTH | |
| Urine 24 Hour | 130 mg/d | 72 MEQ/24hr | 346 mg/24hr | 95 MEQ/24hr | 835 mg/d | |
| Total Urine Volume | 2880 mL | 2880 mL | 2880mL | 2880 mL | 2880 mL | |
| Serum Concentration | 1.6 mg/dL | 4.5 mmol/L | 9.5 mg/dL | 95 mmol/L | 1.3 mg/dL | 27.5 pg/mL |
| Urine Fractional Excretion of Electrolyte | 18% | 34.87% | ||||
| Potassium/Creatinine Ratio | 43 mg/gCr |