Introduction: MCT8 is a specific transporter for the T4 and T3 thyroid hormones that allows their entry in the brain and other organs. Mutations in MCT8 (Allan-Herndon-Dudley syndrome) lead to a severe form of X-linked psychomotor retardation, which is characterised by elevated plasma T3 and low T4.
Aim: We describe the first case diagnosed in Spain with this syndrome and review the published literature about this topic. We both review the various clinical presentations, genetic advances, differential diagnosis and therapeutic perspectives of this syndrome and propose a diagnostic algorithm for it.
Case report: A 5 year-old boy, with a clinical picture compatible with Pelizaeus-Merzbacher disease. PLP1 gene sequencing showed no abnormalities. All the genetic and metabolic studies conducted were normal. Finally, a complete study of thyroid profile revealed abnormalities that were consistent with MCT8 transporter deficiency. The sequencing of the SLC16A2 gene (MCT8) showed a mutation in exon 3 and the study made at a cellular level, has confirmed that this mutation changes the properties of the protein.
Conclusions: In the last five years, there have been many publications about this syndrome, with the identification of more than 50 families worldwide. It is important to both know and suspect this syndrome, because the diagnosis is easy, cheap and accessible (thyroid profile) and, although it has no specific treatment, early diagnosis prevents unnecessary testing and allows to offer genetic counseling to the families affected by it.
Title: Deficiencia del transportador celular de hormona tiroidea MCT8: caso clinico y revision de la bibliografia.
Introduccion. El MCT8 es un transportador especifico para las hormonas tiroideas T4 y T3, que permite su entrada en el cerebro y otros organos. La deficiencia de MCT8, o sindrome de Allan-Herndon-Dudley, es un trastorno ligado a X que, generalmente, se presenta como un cuadro neurologico grave de inicio precoz, con un perfil tiroideo caracteristico (aumento de T3 y disminucion de T4 y rT3). Objetivo. Se presenta el primer caso diagnosticado en España con este sindrome y se revisa la bibliografia publicada, las distintas formas de presentacion clinica, los avances geneticos, el diagnostico diferencial y las perspectivas terapeuticas, y se propone un algoritmo diagnostico. Caso clinico. Varon de 5 años con un cuadro clinico compatible con una enfermedad de Pelizaeus-Merzbacher. La secuenciacion del gen PLP1 no mostro alteraciones. Todos los estudios metabolicos y geneticos realizados fueron normales. Finalmente, un estudio completo del perfil tiroideo revelo alteraciones compatibles con una deficiencia del transportador MCT8. La secuenciacion del gen SLC16A2 (MCT8) mostro una mutacion en el exon 3 y el estudio celular confirmo que esta mutacion cambia las propiedades de la proteina. Conclusiones. En los ultimos años se han multiplicado las publicaciones sobre este sindrome, con la identificacion de mas de 50 familias en el mundo. Es importante conocer este sindrome y sospecharlo, porque el diagnostico es facil, economico y accesible (perfil tiroideo), y, aunque no tiene tratamiento especifico, el diagnostico precoz evita pruebas innecesarias y permite ofrecer consejo genetico a las familias afectadas.