Download Case 084: Malaise, weakness, and muscle pain

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Case 084: Malaise, weakness, and muscle pain
Author:
Thomas YK Chan MD, PhD, FRCP
Affiliation:
The Chinese University of Hong Kong
A 68-year-old woman presented to the Clinic with a 2-month history of malaise, lower
limb weakness, and muscle pain, especially after exercise. She also had aches in
and around the finger joints. Otherwise she did not smoke nor consume alcoholic
beverages and was on aspirin 80 mg daily and metoprolol 50 mg twice daily for
angina pectoris.
On examination, her blood pressure was 112/76 mmHg; pulse rate was regular at 50
beats/minute; and respiratory rate was 20/min. She was alert and orientated.
Proximal muscle weakness was more marked in the lower limbs (grade 4/5) than in
upper limbs (5-/5). Tendon reflexes were normal. There was no joint swelling or
tenderness.
Results of laboratory investigation showed:
Blood counts
Reference range
Hb
10.6
11.5 – 14.3
g/dL
MCV
96
81.0 – 91.0
fL
WBC
5.6
4.0 – 10.8
109/L
Platelet
256
140 – 380
109/L
Na
138
134 – 145
mmol/L
K
3.6
3.5 – 5.1
mmol/L
Urea
4.5
3.4 – 8.9
mmol/L
Creatinine
72
44 – 80
µmol/L
ALT
68
< 58
IU/L
Total bilirubin
15
< 15
µmol/L
Plasma
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ECG showed sinus bradycardia (52 beats/min) with mild ST segment depression in
leads I, aVL and V1 – V4.
Question 1
What is the most likely diagnosis in this patient?
(a) Hypothyroidism
(b) Polymyositis
(c) Primary hypoadrenalism
(d) Myasthenia gravis
(e) Diabetic neuropathy
Question 2
Which 2 of the following diagnostic tests should be ordered?
(a) Electromyography
(b) Thyroid stimulating hormone
(c) Fasting blood sugar
(d) Creatine kinase
(e) Short ACTH stimulation test
Go to end of article for correct answers.
General comments 1
In this elderly woman with myopathy, malaise, bradycardia and anemia,
hypothyroidism should be suspected and was confirmed by a plasma sTSH of 62.3
mIU/L (Reference range: 0.49 – 4.67). Myopathic features in hypothyroidism
commonly involve weakness (usually proximal), myalgias, and cramps. Plasma
creatine kinase levels are elevated in most patients with hypothyroidism to a modest
extent (often less than 1,000 IU/L) and many of whom do not have clinical myopathy.
Our patient’s plasma creatine kinase was 1,137 IU/L (Reference range: 32 – 180).
Creatine kinase elevation can be explained on the basis of myofiber degeneration.
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General comments 2
The red cell production is affected by various hormones, including thyroxine,
glucocorticoids, and testosterone. Endocrine failure is generally accompanied by
mild to moderate anemia. In hypothyroidism, a second etiology of anemia is related
to decreased requirement of oxygen transportation as there is reduction in metabolic
rate and oxygen consumption.
General comments 3
In patients with angina, thyroxine supplement must be given in a smaller than usual
dose (e.g. 25 µg daily). Angina symptoms and ECG should be followed serially and
the dose increased at 4 – 6 week intervals until euthyroid if neither symptoms nor
ECG worsens.
Correct answers
Question 1: (a) Hypothyroidism.
Question 2: (b) Thyroid stimulating hormone.
(d) Creatine kinase.
Further readings
Garber JR et al. Managing the challenges of hypothyroidism. Journal of Family
Practice 2006; 55: S1-8.
Scott KR et al. Hypothyroid myopathy with a strikingly elevated serum creatinie
kinase level. Muscle & Nerve 2002; 26: 141-4.