RESUMO
Hypokalaemic periodic paralysis is a rare genetic neuromuscular disease characterized by episodes of skeletal muscle paralysis associated with low serum potassium. Muscle fibre inexcitability during attacks of paralysis is due to an aberrant depolarizing leak current through mutant voltage sensing domains of either the sarcolemmal voltage-gated calcium or sodium channel. We report a child with hypokalaemic periodic paralysis and CNS involvement, including seizures, but without mutations in the known periodic paralysis genes. We identified a novel heterozygous de novo missense mutation in the ATP1A2 gene encoding the α2 subunit of the Na+/K+-ATPase that is abundantly expressed in skeletal muscle and in brain astrocytes. Pump activity is crucial for Na+ and K+ homeostasis following sustained muscle or neuronal activity and its dysfunction is linked to the CNS disorders hemiplegic migraine and alternating hemiplegia of childhood, but muscle dysfunction has not been reported. Electrophysiological measurements of mutant pump activity in Xenopus oocytes revealed lower turnover rates in physiological extracellular K+ and an anomalous inward leak current in hypokalaemic conditions, predicted to lead to muscle depolarization. Our data provide important evidence supporting a leak current as the major pathomechanism underlying hypokalaemic periodic paralysis and indicate ATP1A2 as a new hypokalaemic periodic paralysis gene.
Assuntos
Paralisia Periódica Hipopotassêmica/genética , Paralisia Periódica Hipopotassêmica/fisiopatologia , ATPase Trocadora de Sódio-Potássio/genética , Animais , Criança , Humanos , Paralisia Periódica Hipopotassêmica/patologia , Masculino , Potenciais da Membrana , Músculo Esquelético/patologia , Mutação de Sentido Incorreto , Potássio/fisiologia , ATPase Trocadora de Sódio-Potássio/fisiologia , Xenopus laevisRESUMO
PURPOSE: This study aims to discuss the diagnosis and management of radial nerve compression neuropathy in the newborn. METHODS: A personal case is presented, followed by a review and analysis of clinically similar cases identified via a PubMed search of published medical literature. RESULTS: We report a case of a term newborn with bilateral radial neuropathy at the humerus level. Despite severe axonal involvement in the electrophysiological evaluation, the patient showed complete bilateral recovery after 3 months of follow-up. CONCLUSIONS: Isolated radial nerve palsy is a rare event in the newborn. The condition does not require surgical treatment and usually proceeds to full and rapid spontaneous recovery.