title: A diagnostic dilemma in a family with cystinuria type B resolved by muscle magnetic resonance.
abstract: BACKGROUND
  Congenital myopathies are inherited primary disorders of the muscle caused by mutations affecting structural, contractile, or regulatory proteins. In the more than 20 genes associated to these conditions, ryanodine receptor type 1 gene (RYR1) is responsible for the most common forms and is associated with a wide range of clinical phenotypes and pathological findings. Magnetic resonance imaging of muscle has been used increasingly to direct genetic testing in myopathies.
  
  
  METHODS
  We describe a consanguineous family affected by cystinuria type B, a metabolic condition linked to chromosome 19q13.2, and a different muscle phenotype that, although related to a congenital myopathy, does not have the striking histological features helping in direct genetic tests.
  
  
  RESULTS
  The assessment of the selective involvement on muscle magnetic resonance imaging allowed the suspicion of RYR1 as the most likely gene responsible for this myopathy. The diagnosis was subsequently confirmed by the finding of a recessive RYR1 mutation.
  
  
  CONCLUSIONS
  The occurrence of congenital myopathy together with cystinuria type B is reported for the first time. The use of muscle magnetic resonance imaging and the homozygosity by descent in SLC7A9, a gene flanking RYR1, allowed us to discover a new mutation in the RYR1 gene.
authors.affiliation: Department of Developmental Neuroscience, IRCCS Stella Maris, Pisa, Italy.
authors.forename: Guja
authors.initials: G
authors.lastname: Astrea
authors.affiliation: The Dubowitz Neuromuscular Centre, UCL Institute of Child Health, London, UK.
authors.forename: Iulia
authors.initials: I
authors.lastname: Munteanu
authors.affiliation: Molecular Medicine, IRCCS Stella Maris Scientific Institute, Pisa, Italy.
authors.forename: Denise
authors.initials: D
authors.lastname: Cassandrini
authors.affiliation: The Dubowitz Neuromuscular Centre, UCL Institute of Child Health, London, UK.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Lillis
authors.affiliation: Molecular Medicine, IRCCS Stella Maris Scientific Institute, Pisa, Italy.
authors.forename: Rosanna
authors.initials: R
authors.lastname: Trovato
authors.affiliation: Neuromuscular Center, Department of Neuroscience, University of Padova, Padua, Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Pegoraro
authors.affiliation: Department of Developmental Neuroscience, IRCCS Stella Maris, Pisa, Italy; Department of Clinical and Experimental Medicine, University of Pisa, Pisa, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Cioni
authors.affiliation: Department of Paediatric Neurology, Catholic University, Rome, Italy.
authors.forename: Eugenio
authors.initials: E
authors.lastname: Mercuri
authors.affiliation: The Dubowitz Neuromuscular Centre, UCL Institute of Child Health, London, UK.
authors.forename: Francesco
authors.initials: F
authors.lastname: Muntoni
authors.affiliation: Department of Developmental Neuroscience, IRCCS Stella Maris, Pisa, Italy. Electronic address: r.battini@fsm.unipi.it.
authors.forename: Roberta
authors.initials: R
authors.lastname: Battini
mesh_terms: D000293:Adolescent; D002648:Child; D003555:Cystinuria / Q000175:diagnosis*; D004252:DNA Mutational Analysis; D005192:Family Health; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D018482:Muscle, Skeletal / Q000473:pathology*; D019837:Ryanodine Receptor Calcium Release Channel / Q000235:genetics
chemical_list: D019837:Ryanodine Receptor Calcium Release Channel
keywords: RYR1; congenital myopathy; cystinuria type B; muscle magnetic resonance