title: Multigene panel next generation sequencing in a patient with cherry red macular spot: Identification of two novel mutations inNEU1gene causing sialidosis type I associated with mild to unspecific biochemical and enzymatic findings.
abstract: BACKGROUND
  Lysosomal storage diseases (LSD) often manifest with cherry red macular spots. Diagnosis is based on clinical features and specific biochemical and enzymatic patterns. In uncertain cases, genetic testing with next generation sequencing can establish a diagnosis, especially in milder or atypical phenotypes. We report on the diagnostic work-up in a boy with sialidosis type I, presenting initially with marked cherry red macular spots but non-specific urinary oligosaccharide patterns and unusually mild excretion of bound sialic acid.
  
  
  METHODS
  Biochemical, enzymatic and genetic tests were performed in the patient. The clinical and electrophysiological data was reviewed and a genotype-phenotype analysis was performed. In addition a systematic literature review was carried out.
  
  
  RESULTS
  Cherry red macular spots were first noted at 6 years of age after routine screening myopia. Physical examination, psychometric testing, laboratory investigations as well as cerebral MRI were unremarkable at 9 years of age. So far no clinical myoclonic seizures occurred, but EEG displays generalized epileptic discharges and visual evoked potentials are prolonged bilaterally. Urine thin layer chromatography showed an oligosaccharide pattern compatible with different LSD including sialidosis, galactosialidosis, GM1 gangliosidosis or mucopolysaccharidosis type IV B. Urinary bound sialic acid excretion was mildly elevated in spontaneous and 24 h urine samples. In cultured fibroblasts, α-sialidase activity was markedly decreased to < 1%; however, bound and free sialic acid were within normal range. Diagnosis was eventually established by multigene panel next generation sequencing of genes associated to LSD, identifying two novel, compound heterozygous variants inNEU1gene (c.699C > A, p.S233R in exon 4 and c.803A > G; p.Y268C in Exon 5 inNEU1transcript NM_000434.3), leading to amino acid changes predicted to impair protein function.
  
  
  CONCLUSIONS
  Sialidosis should be suspected in patients with cherry red macular spots, even with non-significant urinary sialic acid excretion. Multigene panel next generation sequencing can establish a definite diagnosis, allowing for counseling of the patient and family.
authors.affiliation: Department of General Pediatrics, Division of Neuropediatrics and Inherited Metabolic Diseases, University Children's Hospital Heidelberg, Im Neuenheimer Feld 430, 69120 Heidelberg, Germany; Hospital for Children and Adolescents, Centre for Pediatric Research Leipzig (CPL), Department of Women and Child Health, University Hospitals, University of Leipzig, Liebigstraße 20 a, 04103 Leipzig, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Mütze
authors.affiliation: Center for Pediatric Metabolic Medicine, Department of General Pediatrics, University Children's Hospital Heidelberg, Im Neuenheimer Feld 669, 69120 Heidelberg, Germany.
authors.forename: Friederike
authors.initials: F
authors.lastname: Bürger
authors.affiliation: Center for Human Genetics, Paul-Ehrlich-Straße 23, Tübingen, Germany.
authors.forename: Jessica
authors.initials: J
authors.lastname: Hoffmann
authors.affiliation: University Eye Hospital, Department of Head and Dental Health, University Hospitals, University of Leipzig, Liebigstr. 10-14, 04103 Leipzig, Germany.
authors.forename: Helmut
authors.initials: H
authors.lastname: Tegetmeyer
authors.affiliation: Department of Ophthalmology, University Hospital of Martin Luther University Halle-Wittenberg, Ernst-Grube-Straße 40, 06120 Halle (Saale), Germany.
authors.forename: Jens
authors.initials: J
authors.lastname: Heichel
authors.affiliation: Hospital for Children and Adolescents, Centre for Pediatric Research Leipzig (CPL), Department of Women and Child Health, University Hospitals, University of Leipzig, Liebigstraße 20 a, 04103 Leipzig, Germany.
authors.forename: Petra
authors.initials: P
authors.lastname: Nickel
authors.affiliation: Institute of Human Genetics, University of Leipzig Hospitals and Clinics, Leipzig, Germany.
authors.forename: Johannes R
authors.initials: JR
authors.lastname: Lemke
authors.affiliation: Department of General Pediatrics, Division of Neuropediatrics and Inherited Metabolic Diseases, University Children's Hospital Heidelberg, Im Neuenheimer Feld 430, 69120 Heidelberg, Germany; Hospital for Children and Adolescents, Centre for Pediatric Research Leipzig (CPL), Department of Women and Child Health, University Hospitals, University of Leipzig, Liebigstraße 20 a, 04103 Leipzig, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Syrbe
authors.affiliation: Hospital for Children and Adolescents, Centre for Pediatric Research Leipzig (CPL), Department of Women and Child Health, University Hospitals, University of Leipzig, Liebigstraße 20 a, 04103 Leipzig, Germany.
authors.forename: Skadi
authors.initials: S
authors.lastname: Beblo
keywords: DNA, deoxyribonucleic acid; EEG, electroencephalography; Lysosomal storage disease; Multigene panel next generation sequencing; NEU1 gene; Sialidosis; c.699C > A (p.S233R); c.803A > G (p.Y268C)