Thyrotoxic periodic paralysis in Caucasian patients: a diagnostic challenge

A pangenome reference of 36 Chinese populations

Human genomics is witnessing an ongoing paradigm shift from a single reference sequence to a pangenome form, but populations of Asian ancestry are underrepresented. Here we present data from the first phase of the Chinese Pangenome Consortium, including a collection of 116 high-quality and haplotype-phased de novo assemblies based on 58 core samples representing 36 minority Chinese ethnic groups. With an average 30.65× high-fidelity long-read sequence coverage, an average contiguity N50 of more than 35.63 megabases and an average total size of 3.01 gigabases, the CPC core assemblies add 189 million base pairs of euchromatic polymorphic sequences and 1,367 protein-coding gene duplications to GRCh38. We identified 15.9 million small variants and 78,072 structural variants, of which 5.9 million small variants and 34,223 structural variants were not reported in a recently released pangenome reference¹. The Chinese Pangenome Consortium data demonstrate a remarkable increase in the discovery of novel and missing sequences when individuals are included from underrepresented minority ethnic groups. The missing reference sequences were enriched with archaic-derived alleles and genes that confer essential functions related to keratinization, response to ultraviolet radiation, DNA repair, immunological responses and lifespan, implying great potential for shedding new light on human evolution and recovering missing heritability in complex disease mapping.

Parálisis periódica hipokalémica tirotóxica: reporte de un caso y revisión del tema

Se expone el caso de un hombre de 20 años, que consultó a urgencias por cuadro de 2 horas de parestesias y pérdida de la fuerza muscular en miembros inferiores, hasta incapacidad completa para incorporarse desde una silla.  Cinco episodios similares, matutinos, leves, de corta duración, con resolución espontánea, durante los últimos dos meses.  Cuatro meses antes había estado presentando palpitaciones, pérdida de 12 kilos de peso con polifagia, sensibilidad al calor, hiperdefecación y temblor fino en manos.  Se documentó y corrigió hipokalemia.  Se confirmó enfermedad de Graves dando tratamiento con propanolol y 20mCi de I131.  La parálisis periódica hipokalémica tirotóxica (PPHT) es una emergencia y puede presentarse desde debilidad muscular de predominio proximal hasta una parálisis completa con riesgo de muerte secundario a hipokalemia severa.   El diagnóstico se confirma con la presencia de signos clínicos y/ó bioquímicos de tirotoxicosis asociados a hipokalemia.  En la PPHT, hay un incremento de actividad de la bomba Na K – ATPasa dado por un aumento en la estimulación beta adrenérgica asociado a un exceso de hormona tiroidea.   Los factores precipitantes de crisis de PPHT mas frecuentes son la alta ingesta de carbohidratos y el ejercicio extenuante, aunque existen muchos otros más.  Es importante la pesquisa de hipertiroidismo en individuos con parálisis ó debilidad muscular e hipokalemia.  Ésta condición se ha descrito principalmente en hombres asiáticos, pero debe ser considerada también en nuestro medio. 

Novel etiopathophysiological aspects of thyrotoxic periodic paralysis

Thyrotoxicosis can lead to thyrotoxic periodic paralysis (TPP), an endocrine channelopathy, and is the most common cause of acquired periodic paralysis. Typically, paralytic attacks cease when hyperthyroidism is abolished, and recur if hyperthyroidism returns. TPP is often underdiagnosed, as it has diverse periodicity, duration and intensity. The age at which patients develop TPP closely follows the age at which thyrotoxicosis occurs. All ethnicities can be affected, but TPP is most prevalent in people of Asian and, secondly, Latin American descent. TPP is characterized by hypokalemia, suppressed TSH levels and increased levels of thyroid hormones. Nonselective β adrenergic blockers, such as propranolol, are an efficient adjuvant to antithyroid drugs to prevent paralysis; however, an early and definitive treatment should always be pursued. Evidence indicates that TPP results from the combination of genetic susceptibility, thyrotoxicosis and environmental factors (such as a high-carbohydrate diet). We believe that excess T(3) modifies the insulin sensitivity of skeletal muscle and pancreatic β cells and thus alters potassium homeostasis, but only leads to a depolarization-induced acute loss of muscle excitability in patients with inherited ion channel mutations. An integrated etiopathophysiological model is proposed based on molecular findings and knowledge gained from long-term follow-up of patients with TPP.