Paramagnetic Signals in the Globus Pallidus as Late Radiographic Sign of Juvenile-Onset GM1 Gangliosidosis

BACKGROUND: The juvenile form of GM1 gangliosidosis lacks specific physical findings and thus is often a diagnostic challenge for clinicians. T-2 hypodensity in the globus pallidus is a characteristic radiographic sign of neurodegeneration with iron accumulation in the brain that is observed in GM1 gangliosidosis, but the exact timing when this radiographic sign becomes apparent remains to be elucidated. PATIENTS: Two male siblings had normal development until 2 years of age and then developed psychomotor regression with dystonia. Their neuroimaging studies indicated progressive global cerebral atrophy. Exome sequencing identified compound heterozygous missense mutations in GLB1, leading to a diagnosis of GM1 gangliosidosis. RESULTS: A retrospective review of neuroimaging studies revealed that the two patients had strikingly similar clinical courses and radiographic progressions with cortical atrophy that preceded the T-2 hypointensity in the globus pallidus. CONCLUSIONS: Paramagnetic signals in the globus pallidus become apparent relatively late during the disease course, once cerebral atrophy has already become prominent. A comprehensive diagnostic approach involving clinical, radiographic, and genetic testing is necessary for the early identification of affected individuals.