RESUMO
Microtubules are formed from heterodimers of alpha- and beta-tubulin, each of which has multiple isoforms encoded by separate genes. Pathogenic missense variants in multiple different tubulin isoforms cause brain malformations. Missense mutations in TUBB3, which encodes the neuron-specific beta-tubulin isotype, can cause congenital fibrosis of the extraocular muscles type 3 (CFEOM3) and/or malformations of cortical development, with distinct genotype-phenotype correlations. Here, we report fourteen individuals from thirteen unrelated families, each of whom harbors the identical NM_006086.4 (TUBB3):c.785G>A (p.Arg262His) variant resulting in a phenotype we refer to as the TUBB3 R262H syndrome. The affected individuals present at birth with ptosis, ophthalmoplegia, exotropia, facial weakness, facial dysmorphisms, and, in most cases, distal congenital joint contractures, and subsequently develop intellectual disabilities, gait disorders with proximal joint contractures, Kallmann syndrome (hypogonadotropic hypogonadism and anosmia), and a progressive peripheral neuropathy during the first decade of life. Subsets may also have vocal cord paralysis, auditory dysfunction, cyclic vomiting, and/or tachycardia at rest. All fourteen subjects share a recognizable set of brain malformations, including hypoplasia of the corpus callosum and anterior commissure, basal ganglia malformations, absent olfactory bulbs and sulci, and subtle cerebellar malformations. While similar, individuals with the TUBB3 R262H syndrome can be distinguished from individuals with the TUBB3 E410K syndrome by the presence of congenital and acquired joint contractures, an earlier onset peripheral neuropathy, impaired gait, and basal ganglia malformations.
Assuntos
Paralisia Facial/genética , Fibrose/genética , Mutação , Oftalmoplegia/genética , Doenças do Sistema Nervoso Periférico/genética , Tubulina (Proteína)/genética , Anormalidades Múltiplas/genética , Adolescente , Adulto , Substituição de Aminoácidos , Arginina , Criança , Pré-Escolar , Paralisia Facial/diagnóstico , Paralisia Facial/fisiopatologia , Feminino , Fibrose/diagnóstico , Fibrose/fisiopatologia , Histidina , Humanos , Lactente , Masculino , Oftalmoplegia/diagnóstico , Oftalmoplegia/fisiopatologia , Doenças do Sistema Nervoso Periférico/diagnóstico , Doenças do Sistema Nervoso Periférico/fisiopatologia , Síndrome , Adulto JovemRESUMO
Variant forms of the Guillain-Barré syndrome are characterized by their localized or regional involvement of the peripheral and autonomic nerves. As there is no single clinical or serologic marker for Guillain-Barré syndrome, diagnosis of this condition is based upon consistent clinical, laboratory, and neurophysiologic findings, with exclusion of other conditions mimicking this disorder. Recognition of atypical cases enables anticipatory monitoring for disease complications and identifies therapeutic options for affected children. A regional variant with predominant facial, neck, and arm weakness without sensory loss has been reported in adults but only rarely described in childhood. This study reports clinical and neurophysiologic findings in two children with the pharyngeal-cervical-brachial form of Guillain-Barré syndrome. These are the youngest cases of this uncommon disorder reported to date.