Key-words:
Hypokalemia - hypothyroidism - insidious - Libya - renal artery stenosis - Takayasu's
arteritis
Introduction
Takayasu's arteritis (TA) is a chronic vasculitis, characterized by chronic granulomatous
inflammation of the vessel wall of large- and medium-sized arteries with a predilection
for the aorta and its major branches as well as the proximal portions of pulmonary,
coronary, and renal arteries.[[1]] It can lead to progressive stenosis, occlusion, or aneurismal transformation, with
subsequent significant morbidity and mortality.[[1]]
The pathogenesis of TA is still unknown; an interplay of genetics and autoimmune factors
has been suggested.[[2]] It has been described in association with autoimmune disorders, such as systemic
lupus erythematosus, rheumatoid arthritis, systemic sclerosis, ankylosing spondylitis,
granulomatosis with polyangiitis, Crohn's disease, and hyperthyroidism.[[2]],[[3]],[[4]],[[5]],[[6]],[[7]],[[8]] Although the disease has a worldwide distribution, and it is more prevalent among
Eastern and Southeast Asian populations, the prevalence in Japan was 40 cases/million
population compared to 4.7–8.0 per million population in the rest of the globe.[[2]] The clinical manifestation of TA varies depending on the site and severity of vascular
involvement.
A study of the epidemiological and clinical features of TA in Arab countries included
197 patients identified between 1995 and 2012. Among Arabs, the renal artery was involved
in 20%–50% of the patients and hypertension was present in approximately one-third.
None of these patients was from Libya. We report a case of TA diagnosed during medical
evaluation of incidentally discovered hypokalemia in a Libyan patient with hypothyroidism.
Case Report
A 61-year-old Libyan female presented with a medical history of hypothyroidism on
L-Thyroxine replacement since 2012, vitiligo since 1980, and chronic sinusitis. She
has been on regular follow-up at the endocrine clinic. The results of her routine
laboratory studies revealed a low serum potassium level. She denied any constitutional
symptoms. There was no prior history of arthralgias, myalgias, or any other symptoms,
suggestive connective tissue or atherosclerotic peripheral vascular disease. No symptoms
of loss of muscle strength, visual impairment, syncopal episodes, vertigo, or abdominal
pain after eating were observed. No suggestive symptoms of renal or gastrointestinal
Potassium loss were noted. She denied any use of diuretics, laxative, or herbs. Drug
history included intake of levothyroxine 75 μg and simvastatin 20 mg once daily. Her
average blood pressure (BP) recording at the outpatient clinic was 130/80 mmHg, and
she denied taking any antihypertensive medication. She had a history of surgery for
carpal tunnel syndrome in 2012. A discrepancy of kidney size was noted on the ultrasound
abdomen in 2009. The patient reported that there was difficulty in measuring BP in
her right arm. On examination, she looked well, clinically euthyroid, not anemic or
jaundiced. Thinning of the scalp hair and vitiligo patches were present [[Figure 1]]. Her weight was 72.5 kg, height was 151 cm tall, and body mass index was 31.8 kg/m2.
Pulses of the left brachial and radial arteries were not palpable, her pulse rate
was 82 beats/min, and BP in the right arm was 140/90 mmHg and in the left arm was
110/70 mmHg. The rest of the cardiovascular and respiratory examination did not reveal
any abnormalities. The abdomen was soft, lax, with no organomegaly and no renal bruits.
Laboratory parameters are presented in [[Table 1]]. Thyroid and liver function tests were normal. Magnetic resonance angiography revealed
stenosis of both subclavian arteries, thickened abdominal aortic wall, occlusions
of the left renal artery and left common iliac artery, and stenosis of right common
iliac artery [[Figure 2]]. She was referred to the rheumatology clinic for further evaluation and management.
Figure 1: Clinical features suggestive of associated autoimmune diseases. (a) Thinning of scalp
hair, (b) vitiligo patches
Table 1: Some relevant laboratory parameters of the patient and the laboratory reference ranges
Figure 2: Magnetic resonance angiography of the aorta, demonstrating stenosis of both subclavian
arteries, thickened abdominal aortic wall, occlusions of the left renal artery and
left common iliac artery, and stenosis of right common iliac artery
Discussion
TA was named in honor of Japanese Ophthalmologist Mikito Takayasu (1859–1938), who
first reported a case of the disease in 1905.[[9]] TA is a large-vessel vasculitis that involves the aorta and its major branches.
It occurs most commonly in Asia particularly in young females.[[2]] In 1990, the American College of Rheumatology proposed six criteria for the diagnosis
of TA [[Table 2]]. Three out of six criteria are needed for the diagnosis, with a sensitivity of
90.5% and a specificity of 97.8%.[[10]] Angiographic classification[[11]] defined six types of TA based on the anatomic distribution of vascular involvement
is summarized in [[Table 3]]. Angiographic classification correlates with clinical manifestations and prognosis
but cannot differentiate active from burned-out lesions. According to the arterial
angiography study, our patient belongs to Type V, with the involvement of ascending
aorta, aortic arch, and its branches and abdominal aorta and/or renal arteries.
Table 2: The six American College of Rheumatology criteria for the diagnosis of Takayasuʼs
arteritis
Table 3: The angiographic classification of Takayasuʼs arteritis defining six types based
on the anatomic distribution of vascular involvement
Although the disease typically begins in the second or third decades of life, it is
not uncommon in the extremes of age. Soto et al. from Mexico reported 9% of their
patients at diagnosis as aged >40 years; 10.7% of patients studied by Vanoli et al.
were >50 years; 4.9% of patients in a French study were aged >60 years.[[12]],[[13]],[[14]] Time lag to diagnosis is approximately 15 months. A delay in diagnosis of 2–11
years is seen in the West.[[2]] In our patient, the previous ultrasound report of a discrepancy of renal size pointed
to a disease onset beyond 10 years, with a chronic, insidious course.
A recent study of the epidemiological and clinical features of TA among Arab populations
showed female predominance. The age average at onset in most series was 31.5 years,
and the mean delay in diagnosis was 3.5 years (ranged 1.5–4.2 years).[[15]],[[16]] A long delay in the diagnosis, was in part due to the low awareness of a relatively
rare disease.
Patients can present in an early stage of disease activity with constitutional features,
such as fever, nocturnal sweats, weight loss, headache, and malaise; with or without
symptoms caused by vascular stenosis, occlusion, or aneurysms; or may diagnose later
in the “burnout” or chronic stage.[[15]]
Clinical manifestations of the disease vary depending on the sites and severity of
vascular lesions. In our patient, the incidental finding of hypokalemia triggered
re-assessing the patient history, examination, and investigation. Presence of hypokalemia
with a discrepancy in renal size, in an older person with a history of hypertension,
hypothyroidism, and hyperlipidemia, raises the probability of atherosclerosis as the
cause of renal artery stenosis (RAS). The insidious onset of the disease, the absence
of the initial acute inflammatory phase of TA, and the rarity of the condition in
Libyans may have contributed to the delay in the diagnosis.
Conclusions
TA is a rare condition. Only a few cases were reported in the international literature
from Libya.[[17]] The disease was diagnosed in the burned-out stage during evaluation of an incidental
finding of hypokalemia secondary to RAS. Delays in diagnosis can be reduced by carefully
searching for unequal or absent upper extremity pulses and by listening for renal
bruits in hypertensive patients. The disease must be considered in patients who present
with renovascular hypertension, in a context of other autoimmune disorders.
Declaration of patient consent
The author certifies that she obtained all appropriate patient consent forms. In the
form, the patient has given her consent for her images and other clinical information
to be reported in the journal. The patient understands that her names and initials
will not be published and due efforts will be made to conceal their identity, but
anonymity cannot be guaranteed.
Compliance with ethical principles
No prior ethical approval is required for single case reports. However, the patient
provided consent for publication, as stated above.
