[Thyroid hormone resistance may course hypotonia in infancy]

Allan Herndon Dudley's syndrome (AHDS) is X-linked mental retardation and hypotonia caused by mutations in a thyroid hormone transporter gene - MCT8. The typical thyreoidea AHDS profile is elevated T3, low-normal T4 and normal or elevated thyroid stimulating hormone (TSH). Neonatal screening with TSH often does not identify AHDS in boys and therefore it is of paramount importance to screen boys who present with hypo-tonia and/or mental retardation with thyroidea profile. In the case report a four and a half month-old boy with develop-mental delay and hypotonia is described and diagnosed with AHDS. The finding of the typical thyroidea profile leads to the diagnosis which is confirmed by DNA analysis.