Ocular myasthenia gravis in a setting of thyrotoxicosis
A 22-year-old female presented to the Neurology Clinic with a history of a mild, dull aching headache in the occipital area, which progressively increased over the past two years. She also complained of diplopia in all directions for the past six months. A positive history of aura, neck pain, restriction of movement in the neck, vomiting, photophobia, seizures, and weakness of limbs was present. There was also a positive history of amenorrhea since four months, and a 10 kg weight loss over the last four months was documented. Family history suggestive of any thyroid disorder or neuromuscular disease was negative. A general survey of the patient showed a thin built and poorly nourished female with pallor and pedal edema. Vitals recorded: Pulse – 96/minute, regular, with normal volume and character; Blood pressure – 130/90 mm of Hg. The patient was afebrile. Diffuse thyroid swelling was noticed during the examination. Systemic examination including neurological and all other systems documented no significant abnormality, except for decreased palpebral fissure of the left eye and lid lag noticed in the left eye []. Based on the history and examination findings and a battery of relevant investigations (Tensilon test), diagnosis of ocular MG was made, and physostigmine was initially prescribed to the patient. The patient was then referred to Internal Medicine for further evaluation for suspicion of hyperthyroidism. Thyroid function tests reported T3 levels of 3.4 (0.8-2.0) ng/ml, T4 levels of 20.2 (4.5-12.0) ug/dl, and TSH levels of <0.005 (0.3-5) uiu/ml. The hematological and other biochemical investigations were all within normal limits. Finally, in view of the thyrotoxic status of the patient, carbimazole was started at a dose of 10 mg, eight hourly. The patient was discharged with an advice to continue carbimazole and review after one month. Follow-up after one month showed both symptomatic and biochemical improvement, that is, left eye ptosis had decreased and T3, T4, and TSH levels were within normal range, respectively. Follow-up after three months demonstrated complete clinical and biochemical recovery. The further plan was to discuss the alternative of thymectomy with the patient, on the next follow-up after two months.