Cardiovascular Journal of Africa: Vol 28 No 5 (September/October 2017)

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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 5, September/October 2017 e4 AFRICA
Case Report
Liddle’s syndrome in an African male due to a novel
frameshift mutation in the beta-subunit of the epithelial
sodium channel gene
Robert Freercks, Surita Meldau, Erika Jones, Jason Ensor, Clarise Weimers-Willard, Brian Rayner
Abstract
Resistant hypertension is a common clinical problem in South
Africa and is frequently associated with low renin and aldos-
terone levels, especially in black Africans. In South Africa,
novel variants in the epithelial sodium channel (ENaC)
have been described to be associated with varying degrees
of hypokalaemia and hypertension due to primary sodium
retention. We report here a case of Liddle’s syndrome due
to a novel c.1709del11 (p.Ser570Tyrfs*20) deletion in the
beta-subunit of the ENaC in a young black African male.
We discuss the likely pathogenesis of hypertension in this
setting as well as the treatment options available in South
Africa aimed at the ENaC. This case highlights the need for
vigilance in detecting and appropriately treating low-renin
and low-aldosterone hypertension in view of the frequency
of the described variants of the ENaC channel in our coun-
try. Specific therapy such as amiloride should be made more
widely available.
Keywords: hypertension, Liddle’s, Africa, amiloride, resistant
hypertension, hypokalaemia, low renin
Submitted 2/11/16, accepted 12/1/17
Cardiovasc J Afr 2017; 28: e4–e6
DOI: 10.5830/CVJA-2017-012
Case report
An 18-year-old Xhosa-speaking South African male was referred
to the Livingstone Hospital renal unit for evaluation. He first
presented at the age of 17 years to a nearby hospital emergency
unit with a headache. He was not on any chronic or over-the-
counter medications, did not consume liquorice, ethanol or
traditional medications and was a non-smoker. He was noted
to be hypertensive, with a blood pressure of 216/114 mmHg and
hypokalaemic, with a serum potassium level of 2.9 mmol/l (see
Table 1), but he left without treatment.
Eight months later he was seen at the same unit with a similar
presentation and was admitted for further investigations and
treatment. Despite multiple antihypertensive interventions, his
blood pressure remained uncontrolled. At discharge he was
commenced on the following medications: enalapril 10 mg
12 hourly, amlodipine 10 mg daily, furosemide 40 mg twice
daily, atenolol 25 mg daily, hydrallazine 50 mg twice daily and
hydrochlorothiazide 25 mg daily.
He was referred to our unit, and one month later his blood
pressure was 179/118 mmHg in the left arm and 182/113 mmHg
in the right arm, despite adherence to the treatment regime.
He looked well, had a regular pulse rate of 59 beats/min and
weighed 68 kg. The patient gave a history of experiencing
frequent headaches associated with muscle fatigue, but no
myalgias. The muscle fatigue was worse at times when the
headache was present. He also described exertional dyspnoea but
no spells suggestive of phaeochromocytoma. Both his parents
were hypertensive and his father had died of an uncertain cause
before the age of 50 years.
On cardiovascular examination, all pulses were present. There
was no radiofemoral delay or any bruits. The cardiac apex beat Division of Nephrology and Hypertension, Livingstone
Hospital, Port Elizabeth, South Africa
Robert Freercks, MB ChB, FCP (SA), Cert Neph, MPhil, FRCP (Lon)
Jason Ensor, MB ChB, FCP (SA), Cert Neph
Clarise Weimers-Willard, MB ChB
Division of Chemical Pathology, University of Cape Town and
National Health Laboratory Service, Cape Town, South Africa
Surita Meldau, BSc Med (hons), MSc (Med)
Department of Medicine, Division of Nephrology and Hyper-
tension, University of Cape Town, Cape Town, South Africa
Robert Freercks, MB ChB, FCP (SA), Cert Neph, MPhil, FRCP
(Lon),
Erika Jones, MB BCh, PhD, FCP (SA), Cert Neph
Jason Ensor, MB ChB, FCP (SA), Cert Neph,
Brian Rayner, MB ChB, FCP (SA), MMed, PhD
Table 1. Blood results and blood pressure readings
Test 02/2014 10/2015 11/2015 01/2016 03/2016 06/2016 08/2016
Sodium, mmol/l 142 140 139 136
Potassium,
mmol/l
2.9 3.4 2.7 3.5 3.3 3.7 3.7
Creatinine,
umol/l
88 220 150 144 134 153 128
Renin, mIU/l
(9.2–69.7)
6.0 Amiloretic added 03/2016
Aldosterone,
pmol/l (94–757)
48.6
Office BP,
mmHg
216/114 220/120 179/118 173/101 181/121 162/91 142/100