Case Presentation:
A 30 year-old Hispanic male with no past medical history was brought to ER status post fall after sudden onset of muscle weakness in extremities. He experienced mild intermittent muscles cramps and soreness while he was driving a car prior to the onset of the weakness. He had history of similar but lower intensity muscle weakness in the past that got better spontaneously. He denied family history of periodic paralysis, hyperthyroidism and use of herbal products. Physical findings were motor weakness (3/5) on both upper and lower extremity proximal muscle groups, diminished deep tendon reflexes on both knees and hypoactive bowel sounds. Initial labs were remarkable for Potassium 2.1 (3.5-5.1mmol/L), TSH 0.007 (0.35-5.50 mlU/L), free T4 4.2 (0.89-1.76 ng/dL), free T3 19.76 (2.3-4.2pg/ml) and CPK 602 (38-174 IU/L). EKG showed “U” wave in precordial leads. Serum Magnesium level was normal. Positive serum anti-thyroglobulin microsomal antibody, elevated serum thyroid peroxidase antibody and thyroid stimulating immunoglobulin were consistent with Graves’ disease. Treatment with Potassium supplement and propranolol therapy showed a dramatic improvement in muscle power in few hours and subsequently he walked out of the hospital (eloped). Graves’ disease (thyrotoxic), hypokalemia, proximal muscle weakness with at least one previous similar episode (periodic paralysis) with normal urinary electrolytes and absent family history along with rapid correction of muscle weakness after the treatment were consistent with our diagnosis of TPP.
Discussion:
Thyrotoxic Periodic Paralysis (TPP) is characterized by abrupt onset of episodic muscle paralysis secondary to hypokalemia in patients with thyrotoxicosis. TPP is a very rare but can be a sole presentation of Grave’s disease. Early diagnosis and proper management often shows a dramatic improvement of this potential lethal manifestation of hyperthyroidism. The incidence of TPP is rare in non-Asian population. Methimazole or propylthiouracil helps to prevent future attacks of paralysis by correcting underlying hyperthyroid state. The pathogenesis of muscle paralysis in patients with hyperthyroidism is not clearly understood yet, but it seems like a manifestation of a distinct disorder unmasked by the state of thyrotoxicosis. More studies need to be done to better understand this disease entity.
Conclusions:
TPP is a rare initial presentation of a relatively common Graves’ disease. TPP should be considered in the differential diagnosis of patients presenting with acute onset of paralysis or periodic paralysis even in patients with out obvious signs of thyrotoxicosis. TSH and electrolytes should be a part of initial workup in such patients. Treatment with judicious potassium supplement and nonselective beta-blockers and close monitoring of serum potassium to prevent rebound hyperkalemia remain paramount important.