Rare Neurologic Presentation of Thyrotoxicosis

Case Presentation

A 15-year-old girl presented with easy fatigability, tremor, palpitations, and amenorrhea for the past 6 months. She also noticed protrusion of her eyeballs. On physical examination, she was tachycardic and had exophthalmos, fine tremor, and an anterior neck swelling of rubbery consistency. Her thyroid function tests were consistent with thyrotoxicosis, with a low thyroid stimulating hormone (TSH) (0.007 mIU/mL [N, 0.3-4.4]) and elevated free T4 (6 ng/dL [N, 0.89-1.72]). Thyroid ultrasound showed that both lobes and isthmus were enlarged with heterogeneous echo pattern and increased vascularity. No nodules were seen. With the assessment of thyrotoxicosis secondary to Grave’s disease, she was started on propylthiouracil (PTU) 100 mg twice per day and Atenolol 50 mg daily. Atenolol was stopped after 4 months, and PTU was escalated to 200 mg 3 times per day over 5 months.

Six months after her initial presentation, while taking PTU 200 mg 3 times a day and off Atenolol for 2 months, she came with a complaint of involuntary movement of the hands and face for the last 15 days. She still complained of occasional palpitations and had a heart rate of 102 beats/min, but other vital signs were within normal range. The thyroid levels showed T3 toxicosis with 0.041 mIU/mL TSH (N, 0.3-4.5), 10.8 mcg/dL total T4 (N, 5.2-12.7), and 2.19 ng/mL total T3 (N, 0.6-2.15). The following video was recorded.

What is the diagnosis?

Answer

Chorea due to thyrotoxicosis. She was evaluated by neurology department, and they documented that there was involuntary, random movement of eyes, mouth, left hand, and left leg predominantly. She also had difficulty with tongue protrusion and milkmaid’s grip on her left hand. A diagnosis of chorea was made, and she was started on sodium valproate 200 mg daily. Within 3 months, chorea resolved and the medication was stopped. Thyroid function tests were normal at the time of discontinuation (TSH, 1.6 mIU/mL [N, 0.3-4.5]; total T4, 8.4 mcg/dL [N, 5.2-12.7]; and total T3, 1.12 ng/mL [N–0.6- 2.15]), and PTU was maintained at 200 mg 3 times a day over the 3 months. She has been off valproate for 2 months with no recurrence of symptoms.

Chorea, a manifestation of thyrotoxicosis, was first described in 1888 by Sir William Gowers.¹ Since then, there have been various case reports of the condition, but it still remains a rare occurrence.² In our country, this is the first reported case in literature.

Other causes of chorea, such as group A β-hemolytic streptococcus infection leading to Sydenham’s chorea, Huntington’s disease, and certain medications are a more common cause of chorea. In our patient, antistreptolysin O titer was negative and there was no evidence of other manifestations of rheumatic heart disease. There was also no family history of similar illness, and the resolution of chorea, even after sodium valproate was stopped, shows the self-limited course of the disease, making Huntington’s disease an unlikely cause. Although certain medications, including neuroleptics, tricyclic antidepressants, and combined oral contraceptives, have been known to cause movement disorders, our patient had no drug intake other than PTU, which has, so far, not been linked with causing chorea. She had no features of systemic lupus erythematosus and no metabolic disturbance other than the hyperthyroidism that could explain the occurrence of chorea.

Our understanding of the pathophysiology of hyperthyroid-related chorea is still incomplete, but there are certain hypotheses linking it to hypersensitivity of dopaminergic receptors.³

In many instances, patients may present initially with chorea, so, a high clinical suspicion is important in these patients and an investigation with thyroid function tests should not be delayed. We report this case in the hope of raising awareness about the condition and preventing delay in diagnosis when similar cases occur in the future.

Disclosure

The authors have no multiplicity of interest to disclose.