Rare disease centers for periodic paralysis: China versus the United States and United Kingdom.

INTRODUCTION: We have developed a rare disease center in China. METHODS: In this study we analyzed how patients with periodic paralysis accessed centers in China vs. in the USA and UK. RESULTS: A total of 116 patients with periodic paralysis were evaluated in Beijing and Hangzhou (2003-2012). These patients traveled long distances for outpatient specialist care without an appointment or physician referral. In contrast, at the University of Rochester in the USA, >90% of patients were referred from physicians throughout the country by identifying physician expertise or by referrals from a patient advocacy group. In the UK, a single center, supported by the National Health Service, provides assessment/genetic testing for all UK patients. CONCLUSIONS: Rare disease centers in China require: (1) establishing a center for clinical characterization of the disease (e.g., periodic paralysis); (2) establishing a genetic diagnostic platform; (3) placing the center at a major city hospital; and (4) facilitating patient access through internet websites.

Prevalence study of genetically defined skeletal muscle channelopathies in England.

OBJECTIVES: To obtain minimum point prevalence rates for the skeletal muscle channelopathies and to evaluate the frequency distribution of mutations associated with these disorders. METHODS: Analysis of demographic, clinical, electrophysiologic, and genetic data of all patients assessed at our national specialist channelopathy service. Only patients living in the United Kingdom with a genetically defined diagnosis of nondystrophic myotonia or periodic paralysis were eligible for the study. Prevalence rates were estimated for England, December 2011. RESULTS: A total of 665 patients fulfilled the inclusion criteria, of which 593 were living in England, giving a minimum point prevalence of 1.12/100,000 (95% confidence interval [CI] 1.03-1.21). Disease-specific prevalence figures were as follows: myotonia congenita 0.52/100,000 (95% CI 0.46-0.59), paramyotonia congenita 0.17/100,000 (95% CI 0.13-0.20), sodium channel myotonias 0.06/100,000 (95% CI 0.04-0.08), hyperkalemic periodic paralysis 0.17/100,000 (95% CI 0.13-0.20), hypokalemic periodic paralysis 0.13/100,000 (95% CI 0.10-0.17), and Andersen-Tawil syndrome (ATS) 0.08/100,000 (95% CI 0.05-0.10). In the whole sample (665 patients), 15 out of 104 different CLCN1 mutations accounted for 60% of all patients with myotonia congenita, 11 out of 22 SCN4A mutations for 86% of paramyotonia congenita/sodium channel myotonia pedigrees, and 3 out of 17 KCNJ2 mutations for 42% of ATS pedigrees. CONCLUSION: We describe for the first time the overall prevalence of genetically defined skeletal muscle channelopathies in England. Despite the large variety of mutations observed in patients with nondystrophic myotonia and ATS, a limited number accounted for a large proportion of cases.

A case report of familial periodic paralysis.

A 20-year-old male was brought to the hospital with the complaints of severe weakness and inability to move the limbs of 12 hours duration. For the last 2 years he had the same episodes with spontaneous recovery. Family history strongly suggested involvement of other members of the family. Physical examination did not suggest any neurological deficit. All investigations were normal except serum potassium level being 2.2 meq/l during attack and 3.4 meq/l after the attack. He was treated with oral acetazolamide and potassium chloride. The case was diagnosed to be familial periodic paralysis belonged to the group 'episodic myasthenia'.

[Thyrotoxic periodic paralysis: an exceptional case report in Spanish population]. / Parálisis periódica tirotóxica: una observación excepcional en nuestro medio.

Thyrotoxic periodic paralysis is a rare clinical manifestation of thyrotoxicosis in spanish population. Patients show weakness and frecuently, paralysis and low levels of potassium in serum. The episode can be triggered by eating high carbohydrate diet, exercise, stress and some drugs. We present a new case of thyrotoxic periodic paralysis in a Grave's disease patient. Only four cases have been reported in the spanish literature. We conclude that a functional evaluation of thyroid gland is necessary in thyrotoxic periodic paralysis patients.

Familial hypokalaemic periodic paralysis in Finland.

Seven families with familial hypokalaemic periodic paralysis were found in Finland. Nine of the 103 asymptomatic family members studied had abnormal results on a potassium exercise test. The overall prevalence of familial hypokalaemic periodic paralysis in Finland was 0.4/100,000. Carbohydrate intake and hard exercise were the most important triggers of paralytic attacks. Half of the patients reported having attacks at least once a month. Seven patients reported cardiac symptoms (especially bradycardia) during attacks. Permanent muscular weakness was not prominent.

Thyrotoxic periodic paralysis in a hispanic man.

Thyrotoxic periodic paralysis occurs much more frequently in Orientals than in whites, and has rarely been reported in patients of Hispanic descent. A 28-year-old Mexican man presented with acute onset of bilateral lower extremity weakness after ingestion of a large carbohydrate meal. Laboratory investigation revealed severe hypokalemia, with a serum potassium level of 2.1 mmol/L (2.1 mEq/L), and hyperthyroidism. Administration of potassium chloride resulted in normalization of the serum potassium level and resolution of muscle weakness. Treatment with propranolol, and subsequent restoration of a euthyroid state with iodine 131, was effective in preventing further episodes of paralysis. Thyrotoxic periodic paralysis, although rare, may occur in Hispanic patients, and should be considered in the differential diagnosis of muscle weakness in this population.

Familial hypokalemic periodic paralysis in blacks.

Two cases of familial hypokalemic periodic paralysis in Negro brothers occurred, and--because this has been reported to be an unusual disease among blacks--the family pedigree was investigated. Histories were obtained on 79 family members in four generations. Twenty seven (34%) had symptoms of periodic paralysis or weakness. As far as we could determine, there were no Caucasian ancestors.