Case history
A 42-year-old Japanese woman
presented with a 4-week history of myalgia. Two weeks before her visit
to our hospital, her pain began to spread from the neck to the chest,
resulting in extreme myalgia four days prior to her visit. The pain was
sudden, non-persistent, and generalised with no clear localisation.
There was no change in her symptoms owing to diet. The patient reported
excessive sweating and weight loss (5 kg/6 months); however, tremors,
diarrhoea, and diplopia were absent. She had no remarkable family
history, though her medical history included pyelonephritis.
Furthermore, she was not taking any oral medications or supplements.
On examination, the patient appeared ill and was afebrile (37.0 °C). Her
blood pressure was 110/64 mmHg, pulse 90/min, respiratory rate 16/min
with an O2 saturation of 98% on room air. Physical
examination revealed no ocular protrusion or eye movement disorder. Her
thyroid gland was diffusely enlarged, but there was no associated
tenderness or nodule present. Her
cardiac examination results were normal, and lungs were clear on
auscultation. There were no abnormal abdominal findings. Findings of
neurological examinations, including tests for muscle weakness, muscle
grasping pain, muscle atrophy, and deep tendon reflexes, were completely
unremarkable.
On admission, initial investigations revealed mild anaemia. Inflammatory
markers and kidney function test results were normal, but liver function
test values were mildly elevated. Creatinine kinase, serum calcium, and
serum phosphate levels were normal. Further examination revealed free
triiodothyronine (FT3) > 30.00 ng/mL, free thyroxine (FT4)
3.45 ng/mL, TSH < 0.01 µIU/mL, and findings of thyrotoxicosis.
Additionally, she tested positive for TRAb (6.4 IU/L). The results of
tests for autoantibodies, including antinuclear antibodies, were
negative (Table 1).
Cervical ultrasonography showed diffuse enlargement of the thyroid gland
and increased blood flow with a colour Doppler scan of 57.6 cm/s and
48.1 cm/s on the right and left, respectively. Consequently, she was
diagnosed with Basedow’s disease. Since there were no specific symptoms
and autoantibodies were absent, we concluded that there was no
complication of myositis. Treatment with mercazole 15 mg and potassium
iodide 50 mg was initiated, leading to an improvement in FT3
(> 4.49 ng/mL) and FT4 (1.31 ng/mL) levels after one month
of treatment. Myalgia disappeared one week after the administration of
the anti-thyroid medication. Thereafter, the condition of the patient
improved without any relapse of pain.