Males with Allan-Herndon-Dudley syndrome [OMIM #30523], also known as MCT8-specific thyroid hormone cell transporter (THCT) deficiency, MCT8 deficiency, syndromic X-linked mental retardation with high serum T3, and thyroid hormone cell transport defect, have severe developmental delay, gait disturbance, dystonia, and poor head control. Patients with this condition also have a thyroid hormone defect presenting with unusual combination of increased serum 3,3’,5-triiodothyronine (T3), decreased serum thyroxine (T4) and low 3,3’,5’-triiodothyronine (reverse T3, rT3) concentrations found in both males and to a lesser degree in carrier females. However, T3 and reverse T3 are not commonly measured and normal ranges for children are not available in routine laboratories. Mutations of the SLC16A2 (MCT8) [OMIM #300095] gene, or monocarboxylate transporter 8, have been identified in patients with Allan-Herndon-Dudley syndrome.
All samples will undergo thyroid hormone testing in Dr. Refetoff’s Endocrinology Laboratory at the University of Chicago to examine the presence of thyroid hormone abnormalities before SLC16A2 sequencing. To date, all patients with SLC16A2 abnormalities have demonstrated thyroid hormone abnormalities.
Contact the MCT8 Organization (http://www.mct8organization.org) for more information and support.