INTRODUCTION: Allan-Herndon-Dudley syndrome is an X-linked condition caused by 
mutations of the monocarboxylate transporter 8 gene. This syndrome is 
characterized by axial hypotonia, severe mental retardation, dysarthria, 
athetoid movements, spastic paraplegia, and a typical thyroid hormone profile. 
In most of the cases reported so far, brain magnetic resonance imaging showed 
delayed myelination of the central white matter and this finding greatly affects 
the diagnosis of the syndrome.
CASE REPORT: We present a new case studied with magnetic resonance imaging and 
spectroscopy and we reviewed all the articles published between 2004 and 2012 
containing information on brain neuroimaging in this syndrome. An Italian boy, 
showing a classical phenotype of the syndrome, was diagnosed at 17months of age. 
Genetic analysis revealed a new frameshift mutation of the monocarboxylate 
transporter 8 gene. His brain magnetic resonance imaging and spectroscopy, 
performed at the age of 14months, were normal.
DISCUSSION: Among the 33 cases reported in the literature, 3 cases had normal 
neuroimaging and in 7 of 14 cases, having a longitudinal follow-up, the initial 
finding of delayed myelination gradually improved. Our case and the review of 
the pertinent literature suggest that Allan-Herndon-Dudley syndrome should be 
suspected in males with the typical neurological and thyroid profile, even in 
cases with normal brain myelination.