Thyrotoxic periodic paralysis in an Italian man: clinical manifestation and genetic analysis

In Western countries, thyrotoxic periodic paralysis (TPP) is a rare condition with only sporadic cases described so far. Here, we describe a 29-year-old Italian man who presented with leg weakness and hypokalaemia. Treatment with intravenous potassium resulted in a rapid resolution of symptoms. TPP as the underlying cause was suggested by suppressed thyroid-stimulating hormone (TSH), elevated free T3 and free T4, and the presence of TSH-receptor antibodies (TRAB). Genetic analysis showed no mutations in the candidate exons of calcium (CACN1AS), potassium (KCNE3) and sodium (SCN4A) channel genes. However, we identified the presence of two single nucleotide polymorphisms (SNPs), 1491 C > T and 1551 T > C, in exon 11 of the CACN1AS gene. Although the 1491 C > T SNP is not apparently involved in the pathogenesis of the disease, the 1551 T > C SNP has been associated with TPP in Asians and reported in only one case in European Caucasians. Further investigations are needed to clarify whether such polymorphisms have a role in the disease pathogenesis in Caucasians.