title: Genotypic and phenotypic features of McArdle disease: insights from the Spanish national registry.
abstract: BACKGROUND
  Published genotype/phenotype data on McArdle disease are limited in sample size. A single national (Spanish) registry of patients with McArdle disease was created with the purpose of analysing their genotypic and phenotypic characteristics.
  
  
  METHODS
  A cross sectional study was conducted, collecting demographic, family history, clinical, genotype and functional capacity data from all patients diagnosed with McArdle disease in the Spanish National Health System up to December 2010.
  
  
  RESULTS
  239 cases were recorded (all of Caucasian descent, 102 women; mean±SD age 44±18 years (range 9, 93)); prevalence of ∼1/167 000 people. Two mutant PYGM alleles were identified in 99.6% of cases. Although there was heterogeneity in the severity of symptoms, there were four common diagnostic features: (1) 99.5% of patients reported a history of acute crises of exercise intolerance (accompanied by recurrent myoglobinuria in 50% of cases); (2) in 58% of patients, symptoms started in the first decade of life; (3) 86% of patients repeatedly experienced the 'second wind' phenomenon over life; and (4) 99% of patients had a high basal serum level of total creatine kinase (>200 U/l). Clinical presentation of the disease was similar in men and women and worsened with age. Patients who were physically active had higher levels of cardiorespiratory fitness (by 23%, p=0.003) and were more likely to improve their clinical course over a 4 year period compared with inactive patients (OR 225; 95% CI 20.3 to 2496.7).
  
  
  CONCLUSIONS
  The main clinical features of McArdle disease are generally homogeneous and frequently appear during childhood; clinical condition deteriorates with ageing. Active patients have a better clinical outcome and functional capacity.
authors.affiliation: Universidad Europea de Madrid, Madrid, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Lucia
authors.forename: Jonatan R
authors.initials: JR
authors.lastname: Ruiz
authors.forename: Alfredo
authors.initials: A
authors.lastname: Santalla
authors.forename: Gisela
authors.initials: G
authors.lastname: Nogales-Gadea
authors.forename: Juan C
authors.initials: JC
authors.lastname: Rubio
authors.forename: Inés
authors.initials: I
authors.lastname: García-Consuegra
authors.forename: Ana
authors.initials: A
authors.lastname: Cabello
authors.forename: Margarita
authors.initials: M
authors.lastname: Pérez
authors.forename: Susana
authors.initials: S
authors.lastname: Teijeira
authors.forename: Irene
authors.initials: I
authors.lastname: Vieitez
authors.forename: Carmen
authors.initials: C
authors.lastname: Navarro
authors.forename: Joaquín
authors.initials: J
authors.lastname: Arenas
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Martin
authors.forename: Antoni L
authors.initials: AL
authors.lastname: Andreu
mesh_terms: D000203:Activities of Daily Living; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D002648:Child; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D005838:Genotype; D024982:Glycogen Phosphorylase, Muscle Form / Q000235:genetics; D006012:Glycogen Storage Disease Type V / Q000235:genetics* / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000473:pathology; D009212:Myoglobinuria / Q000473:pathology; D010641:Phenotype; D012042:Registries; D013030:Spain; D055815:Young Adult
chemical_list: D024982:Glycogen Phosphorylase, Muscle Form