Allan-Herndon-Dudley-Syndrome: An Overview of an Extremely Rare Disorder in Childhood

Abstract

Allan-Herndon-Dudley syndrome (AHDS) is a rare X-linked disease with severe neuropsychiatric abnormalities including psychomotor retardation, lack of speech development, dystonia, and severe intellectual deficits. William Allan, Florence C. Dudley, and C. Nash Herndon first described a syndrome which results from the disturbed formation of two thyroid hormone transporters, MCT8 and Oatp1c1. Nearly 320 individuals of around 130 families have been described so far with MCT-8 deficiency. The first individual treatment attempt with LT4 and Propylthiouracil was introduced in 2008; the development of therapies for Allan-Herndon-Dudley syndrome has gained momentum in recent years. Treatment options range from symptomatic interventions, including botulinum toxin injections, levodopa/carbidopa, assistive devices, functional therapies, rehabilitation to replacement therapies (LT3, LT4, DIPTA, TRIAC, TETRAC), and gene therapy. Diagnosis, treatment and cure of Allan-Herndon-Dudley syndrome in childhood remains challenging for the future. Due to the low number of cases, conducting large-scale studies is challenging, and therefore, it is difficult to find clear guidelines for this extremely rare disease in childhood.