Hypokalaemia and paralysis in the Thai population.

BACKGROUND

Hypokalaemia with paralysis is a syndrome common in Thailand. This syndrome may result from hypokalaemic periodic paralysis (HypoPP), thyrotoxic periodic paralysis (TPP) or distal renal tubular acidosis (dRTA). We prospectively investigated the nature of this syndrome in afflicted Thai patients.

METHODS

Blood and urine samples were collected from 47 patients during attacks for multiple biochemical and thyroid function tests. A long acid loading test was performed in all euthyroid patients. Mutation analyses were done in all HypoPP and TPP patients.

RESULTS

Of the subjects, 34 completed the study. Of those, 11 (32%), eight (24%) and 15 (44%) had TPP, dRTA and HypoPP, respectively. Patients with dRTA and TPP were older than those with HypoPP. Males were more prevalent than females in HypoPP and TPP; the reverse was true for dRTA. Two-thirds of the HypoPP cases were sporadic. The majority of the HypoPP and dRTA patients resided in northeastern Thailand. Of the 11 TPP patients, nine (82%) had no previous thyroid disease. Moreover, four out of 11 patients (36%) had subtle clinical signs of hyperthyroidism; three of eight dRTA patients had renal stones, nephrocalcinosis or both. Only two patients had metabolic acidosis at the time of presentation. No common mutations were found in the HypoPP and TPP patients.

CONCLUSIONS

In most of our patients, HypoPP is sporadic and not associated with the common mutations reported previously. Clinical clues that can assist in differentiating between the causes of hypokalaemia and paralysis are age at onset, gender and geographic region residence of the patients. However, the absence of previous histories of thyroid disease or overt thyrotoxicosis, and of stone disease/nephrocalcinosis or metabolic acidosis does not exclude the diagnosis of TPP or dRTA.