A novel monocarboxylate transporter 8 gene mutation as a cause of severe neonatal hypotonia and developmental delay.
Monocarboxylate transporter 8 acts as a specific cell membrane transporter for thyroxine and especially triiodothyronine into target cells. It is expressed in brain neurons and in many other tissues. The monocarboxylate transporter 8 gene resides on chromosome Xq13.2. An 11-month-old male infant was referred because of severe hypotonia from early life and global developmental delay. Thyroid-function tests showed normal thyrotropin levels and the characteristic for the disorder, including high serum triiodothyronine and low thyroxine concentrations. Molecular analysis of the monocarboxylate transporter 8 gene showed that the patient was hemizygous for a novel missense mutation P537L. This case highlights the importance of determining thyroid hormone levels, especially triiodothyronine, in infants with severe neonatal hypotonia.
Papadimitriou
Anastasios
A
Pediatric Endocrinology Unit, Third Department of Pediatrics, University of Athens School of Medicine, Attikon University Hospital, Rimini 1, Haidari, Athens 124 62, Greece. anpapad@med.uoa.gr
Dumitrescu
Alexandra Mihaela
AM
Papavasiliou
Antigone
A
Fretzayas
Andreas
A
Nicolaidou
Polyxeni
P
Refetoff
Samuel
S
D002658:Developmental Disabilities / Q000175:diagnosis / Q000235:genetics*; D005500:Follow-Up Studies; D018507:Gene Expression Regulation, Developmental; D020022:Genetic Predisposition to Disease; D006801:Humans; D007223:Infant; D008297:Male; D027501:Monocarboxylic Acid Transporters / Q000235:genetics*; D009123:Muscle Hypotonia / Q000175:diagnosis / Q000235:genetics; D020125:Mutation, Missense; D020914:Myopathies, Structural, Congenital / Q000175:diagnosis / Q000235:genetics*; D018570:Risk Assessment; D012720:Severity of Illness Index; D013960:Thyroid Function Tests
D027501:Monocarboxylic Acid Transporters