title: GM1 gangliosidosis type 2 in two siblings.
abstract: A sister and brother, now aged 7 and 9 years, presented with developmental arrest, gait disturbance, dementia, and a progressive myoclonic epilepsy syndrome with hyperacusis in the second year of life. Then, spastic quadriparesis led to a decerebrate state. In the absence of macular or retinal degeneration, organomegaly, and somatic-facial features suggesting mucopolysaccharidosis, the presence of hyperacusis together with sea-blue histiocytes in bone marrow biopsies and deficient beta-galactosidase activity but normal glucosidase, hexosaminidase, and neuraminidase activity on lysosomal enzyme assays constitutes the clinical-pathologic-biochemical profile of GM1 gangliosidosis type 2. This is a rare, late infantile onset, progressive gray-matter disease in which beta-galactosidase deficiency is largely localized to the brain, though it can be demonstrated in leukocytes and cultured skin fibroblasts. It must be distinguished from the Jansky-Bielschowsky presentation of neuronal ceroid lipofuscinosis, mitochondrial encephalopathy, lactic acidosis, strokelike episodes (MELAS) and myoclonic epilepsy with ragged-red fibers (MERRF) syndromes, atypical presentations of GM2 gangliosidoses (Tay-Sachs and Sandhoff's diseases), primary sialidosis (neuraminidase deficiency), galactosialidosis, and Alpers' disease.
authors.affiliation: Department of Pediatrics, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia.
authors.forename: G G
authors.initials: GG
authors.lastname: Gascon
authors.forename: P T
authors.initials: PT
authors.lastname: Ozand
authors.forename: R E
authors.initials: RE
authors.lastname: Erwin
mesh_terms: D001706:Biopsy; D001853:Bone Marrow / Q000473:pathology; D001928:Brain Diseases, Metabolic / Q000175:diagnosis / Q000235:genetics*; D002648:Child; D004831:Epilepsies, Myoclonic / Q000175:diagnosis / Q000235:genetics*; D005260:Female; D016537:Gangliosidosis, GM1 / Q000175:diagnosis / Q000235:genetics*; D006801:Humans; D008297:Male; D009460:Neurologic Examination; D010641:Phenotype