The present two patients are the first reported to have clearly demonstrated both extraneuronal brown pigment deposition and system neurodegeneration as neuropathological features of PME with SCARB2 mutations.
Our patients with SCARB2 mutations showed the clinical and neurophysiologic phenotype of PME, in which epilepsy could be extremely severe, extending the spectrum reported in the typical AMRF syndrome.
A deficiency of human LIMP-2, a receptor for lysosomal mannose 6-phosphate-independent targeting of the beta-glucosidase (betaGC), due to mutations in the SCARB2 gene was described only in six families presented with progressive myoclonic epilepsy and nephrotic syndrome.
We hypothesized that mutations in SCARB2 might account for unsolved cases of progressive myoclonus epilepsy (PME) without renal impairment, especially those resembling Unverricht-Lundborg disease (ULD).