Investigators from VU Medical Centre, Amsterdam, The Netherlands, identified seven patients with severe encephalopathy who shared a previously undescribed MRI pattern with cystic degeneration of the white matter and progressive cerebral, cerebellar and brainstem atrophy. All patients showed rapid deterioration of brain function soon after birth, followed by respiratory failure and death. Whole-exome sequencing revealed pathogenic, heterozygous missense mutations in the SLC19A3 gene, encoding the second thiamine transporter. Pathology of brain tissue demonstrates cerebral atrophy and lesions similar to Leigh’s syndrome. This new, severe, lethal phenotype broadens the phenotypic spectrum of SLC19A3 mutations and is recognized by the associated MRI pattern of brain degeneration. 
COMMENT. MRI pattern of initial swelling with T-hyperintensities followed by rapid degeneration and brain atrophy allows early diagnosis of a rapidly progressive infantile encephalopathy caused by SLC19A3 mutations.