Nonfamilial Hypokalemic Periodic Paralysis and Thyrotoxicosis in a 16-Year-Old Male

Familial periodic paralysis (FPP), both the hypo- and hyperkalemic variants, is a relatively rare inherited disorder but nevertheless is known to most pediatricians. On the other hand, nonfamilial hypokalemic periodic paralysis associated with thyrotoxicosis (TPP) apparently has not been reported in the pediatric literature. The disorder has been described most frequently in Asian males. A total of 2% of thyrotoxic patients in China and Japan were reported to have this complication, and of these, 23 of the 25 patients were males.¹ In the United States, the incidence of TPP in a non-Asian ethnic population is approximately one-tenth that found in Asian countries,² but it also predominates in males.³ The clinical picture is identical to that of FPP, except that associated hyperthyroidism is an absolute requirement. The typical presenting manifestation is the onset of generalized paralysis, more severe in the lower extremities and in the early morning, often occurring after strenuous exercise and/or a high-carbohydrate meal. Although most attacks resolve spontaneously and leave no residual weakness, cardiac arrhythmias can be life-threatening.^4-6Recovery can be hastened by the administration of potassium. Symptoms of hyperthyroidism may be minimal or nonexistent.²Laboratory findings include low potassium and elevated creatine phosphokinase concentrations in serum;⁷electrocardiographic changes characteristic of hypokalemia may be present,⁴ and abnormal thyroid function studies are found.