Abstract Details

Title Thyrotoxic Periodic Paralysis: An Unusual Presentation of Hyperthyroidism in a 20 year-old Male

Topic Neuromuscular and Clinical Neurophysiology (EMG)

Presentation(s) P5 - Poster Session 5 (5:30 PM-6:30 PM)

Poster/Presentation
Number 12-020

Objective Case Diagnosis: Thyrotoxic Periodic Paralysis

Background A 20-year-old man with a medical history of T-cell leukemia status post last chemotherapy in 2009 and in remission, who presented for neuromuscular evaluation of recurrent episodes of sudden symmetric lower extremity (LE) weakness. He had three episodes over a 6-month period with similar presentations. He developed LE weakness and heaviness while attempting to rise from a seated position, during daytime hours, developed difficulty with standing and ambulation, and symptoms resolved spontaneously after several hours. Routine blood tests showed low-normal potassium levels. Thyroid function tests demonstrated thyrotoxicosis with free T4 2.55 (normal 0.90 -1.70 ng/dL) and TSH < 0.01 (normal 0.30 – 4.20 microInternational Units/mL). Further evaluation including total spine MRI and peripheral neuropathy work up were normal. EMG/NCS showed no electrodiagnostic evidence of a large fiber peripheral neuropathy or myopathy, and absence of myotonia. Short and long exercise tests were normal.

Design/Methods

Not applicable

Results Approximately 2% of patients of Asian descent with thyrotoxicosis develop TPP. The incidence in the United States is 0.1%. Diagnosis of TPP is based on a history of recurrent episodes of proximal muscle weakness, affecting mainly the lower limbs, with hypokalemia during attacks and normal potassium levels in between. Grave’s disease is the most common cause of hyperthyroidism in TPP. Pathogenesis is related to a loss-of-function KCNJ18 (Kir2.6) channel mutation. Kir2.6 is a skeletal muscle-specific K inward rectifying channel and predisposes these patients to acute paralytic attacks. Management of hyperthyroidism abolishes TPP attacks.

Conclusions This case highlights the importance of a thorough history, physical exam, and ancillary testing in the diagnosis of TPP. This patient had follow up with an endocrinologist to investigate the underlying etiology and definitive treatment. If not readily recognized, TPP may lead to life-threatening complications such as ventricular arrhythmia and respiratory failure.

Authors/Disclosures
PRESENTER	No disclosure on file
Muhammad Al-Lozi, MD (Washington University in Saint Louis)	Dr. Al-Lozi has nothing to disclose.

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