|Year : 2020 | Volume
| Issue : 1 | Page : 22-24
Hypokalemia and metabolic alkalosis in an Egyptian boy with Pendred syndrome
Kotb Abbass Metwalley1, Hekma Saad Farghaly1, Mohamed Kotb Abbass Metwalley2
1 Department of Pediatrics, Faculty of Medicine, Assiut University, Assiut, Egypt
2 Undergraduate Medical Student, Armed Forces College of Medicine, Cairo, Egypt
|Date of Submission||14-Mar-2020|
|Date of Acceptance||15-Mar-2020|
|Date of Web Publication||24-Apr-2020|
Prof. Kotb Abbass Metwalley
Department of Pediatrics, Faculty of Medicine, Assiut University, Assiut
Source of Support: None, Conflict of Interest: None
Pendred syndrome (PDS) is manifested by congenital sensorineural deafness in association with goiter due to defective organic binding of iodine in the thyroid gland. Herein, we report on an unusual case of a 14-year-old Egyptian boy with PDS presenting with hypokalemia and metabolic alkalosis.
Keywords: Alkalosis, hypokalemia, Pendred syndrome
|How to cite this article:|
Metwalley KA, Farghaly HS, Metwalley MK. Hypokalemia and metabolic alkalosis in an Egyptian boy with Pendred syndrome. Thyroid Res Pract 2020;17:22-4
|How to cite this URL:|
Metwalley KA, Farghaly HS, Metwalley MK. Hypokalemia and metabolic alkalosis in an Egyptian boy with Pendred syndrome. Thyroid Res Pract [serial online] 2020 [cited 2020 Dec 1];17:22-4. Available from: https://www.thetrp.net/text.asp?2020/17/1/22/283216
| Introduction|| |
Pendred syndrome (PDS) (OMIM 274600) is one of the most common autosomal recessive disorders of hearing, characterized by mild-to-severe sensorineural hearing impairment (sensorineural hearing loss) and goiter. It is due to biallelic mutations in SLC26A4. This gene encodes pendrin, a member of the SLC26 family of multifunctional membrane-spanning anion transporters. Pendrin was shown to be expressed in the inner ear, thyroid, and kidney. In the cochlea, it acts as a chloride/bicarbonate exchanger where it contributes to endolymph homeostasis, whereas in the thyroid, it mediates iodide transport at the apical membrane of thyrocytes. Renal affection in children with PDS was only reported in one child; herein, we describe a child with PDS presented with hypokalemia and metabolic alkalosis.
| Case Report|| |
A 14 year old Egyptian boy known to have PDS [Figure 1] was referred to our institution for the evaluation generalized weakness associated with polyuria of 5-month duration. Apart from thyroxin treatment for mild hypothyroidism, he was not receiving any other medication. There was no history of vomiting or gastrointestinal disease, and abuse of diuretics or laxatives was also denied. He was the second-born male child to consanguineous Egyptian parents, with the other sibling being normal. He was diagnosed to have PDS with goiter, deafness, and mutism at the age of 6 years. Physical examination at the time of admission revealed a height of 155 cm (50th percentile), weight of 33.5 kg (25th percentile), and blood pressure of 110/60 mmHg, with the rest of the general and systemic examinations being within normal limits. He had a big goiter with multiple palpable nodules [Figure 2]. Neither the goiter was tender, nor bruit was found on auscultation. Ultrasound examination confirmed multinodularty. Indirect laryngoscopy confirmed mobile both vocal cords Thyroid scan reported a euthyroid multinodular goiter, and perchlorate test showed abnormal organification of nonorganic iodine (about 45%). Audiological examination showed bilateral profound hearing loss (PTA >100 dB). Moreover, magnetic resonance imaging of the temporal bones showed enlarged vestibular aqueducts and bilaterally dilated endolymphatic sacs. Laboratory tests showed a free thyroxine level of 13 pmol/l (normal value: 9–20 pmol/l) and a thyroid-stimulating hormone level of 2.5 mU/l (normal value: 0.15–5.0 mU/l). His fasting blood sugar and renal function are within normal range. He had hypokalemia (2.2 mEq/l), hypocalcemia (8.1 mg/dl), and hypomagnesemia (0.2 mg/dl). Initial arterial blood gas measurements indicated a severe metabolic alkalosis with hypoventilation: pH – 7.52, pO2– 7.05 kPa, pCO2– 6.48 kPa, bicarbonate (HCO3) – 43 mmol/l, and base excess + 6 (normal ranges: 7.36–7.44; 9.3–13.3 kPa; 4.5–6.0 kPa; 22–26 mmol/l; and −3 to +3, respectively). Based on the above mentioned findings, a diagnosis of Pendred with metaboloic alkalosis was made. He was treated with oral KCl, Mg oxide, amiloride, and spironolactone 100–200 mg to maintain her electrolytes in or near normal range.
|Figure 2: A 14-year-old Egyptian boy with Pendred syndrome with multinodular goiter|
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| Discussion|| |
PDS was clinically recognized and concisely described in 1896 by the English general practitioner Vaughan Pendred (1869–1946). A century later in 1997, Coyle et al. discovered the gene for PDS. This gene is located on the long arm of chromosome. Until now, more than 80 mutations in the PDS gene have been described, mostly missense mutations, but also truncations. It is inherited as an autosomal recessive trait.
Our index case was presented with generalized weakness and polyuria which can be explained by hypokalemia which was long lasting to cause these symptoms. This unusual clinical presentation indicates that pendrin does play a part in maintaining acid–base homeostasis in humans, with its absence and consequent failure of renal bicarbonate excretion, leading to metabolic alkalosis, hypokalemia, and hypomagnesemia.
Pendrin is localized in the connecting tubule and in the collecting duct of the kidney cortex, and in particular, at the apical membrane of a subpopulation of intercalated cells (type B and non-A non-B). These cells carry out a fine regulation of acid–base excretion through bicarbonate-transport processes. The reduction of urinary bicarbonate excretion and the development of a metabolic alkalosis found in PDS-knockout animals further strengthen this hypothesis. Accordingly, pendrin expression is inversely correlated to urinary chloride excretion; indeed, it is increased when urinary excretion of chloride is low and decreased when the urinary chloride excretion is high.
| Conclusion|| |
This report highlights the impotence regular laboratory follow-up of children with PDS for early detection and treatment of metabolic alkalosis and hypokalemia that may be associated with PDS.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]