Allan-herdon-Dudley syndrome

초록

Allan Herndon Dudley syndrome(AHDS) is x-linked recessive disorder caused by mutation in SLC16A2 gene located at Xq13.2. SLC16A2 gene encode MCT8 protein, vital for transporting T3 to brain but not rate limiting to peripheral. AHDS is characterized by severe neurodevelopmental delay, hypotonia, failure to thrive, tachycardia with abnormal thyroid function test. Herein, we report a boy with Allan Herndon Dudley syndrome. A 5-month- old boy was consulted for evaluating failure to thrive. He was hospitalized with cough for 2 months. His height was 65.2cm(36.9p), weight was 6kg (2.3p) and head circumference was 42.6cm (50p). He was born at 39+5weeks, 4.46kg (98.1p) and no perinatal problem. He had poor oral sucking power without head control. T3 was mild elevated (252.2ng/ml, normal - <1yr: 85-250, child >1yr: 119-218), free T4(1.2ng/dl) and TSH (2.46mIU/L) were normal. At 10-month-old, he was diagnosed as central hypothyroidism (TSH 2.97mIU/L, Free T4 0.64ng/dl) and started levothyroxine(LT4). There was no increase in body weight after 2 months of levothyroxine administration (6.6kg, <0.1p). TFT result was high T3(336.6ng/ml) normal free T4(1.12ng/dl), low TSH (0.05mIU/L). While adjusting the LT4 dose according to the TFT results, the patient lost follow-up. The patient was revisited at the age of 3, LT4 was re-administered due to severe developmental delay and hypothyroxinemia(free T4 0.64ng/dl) But after taking LT4 for 6month, free T4(0.66ng/dl) was still low and T3(283ng/ml) was elevated. Dystonic movement were observed. The patient underwent CMA and WES, but there were no significant abnormal findings. At 4.5years old, he was diagnosed as AHDS by whole genome sequencing result Xq13.2 microdeletion(2.86KB) SLC16A2 gene. He stopped LT4 and observation of Thyroid test. Free T3/T4 ratio (1.925) and T3 (213.9) were elevated, TSH(3.33mIU/L) was normal and Free T4 was low(0.86ng/dl). As other syndrome of resistant to thyroid hormone, only genetic testing can diagnose A