title: Myotonic dystrophy in a female with myasthenia gravis.
abstract: The likelihood of coexistence in the same patient of myasthenia gravis and myotonic dystrophy has been estimated at 1 in 40 million. The case of a patient in whom both diagnoses were made is reported here. A 13-year-old girl was diagnosed with myasthenia gravis because of weakness, fluctuating fatigability, and mild difficulty with chewing and swallowing. She had ptosis, with weakness predominantly of her face, arms, and neck. Serum antibodies against acetylcholine receptors were 9.9 nmol/L. She was started on pyridostigmine, with significant clinical improvement, reassuming normal daily activities. Two years later, generalized weakness reappeared and reappraisal of her symptomatology disclosed tongue percussion and hand action myotonia. Molecular genetic analysis disclosed 550 repeats of cytosine-thymidine-guanosine triplets on the DMPK gene. Undiagnosed relatives had expansions ranging from 110 to 1000 repeats. Myotonic dystrophy is considered the most common muscular dystrophy, with highly variable clinical manifestations; mildly affected individuals may escape clinical detection. Myasthenia gravis has an estimated prevalence of 15 per 100,000. No studies on the epidemiology of these diseases have been done in Chile. Although both diseases have specific clinical and laboratory presentations, they share some features in the mode of presentation that may generate difficulty in diagnosis of both entities in the same patient.
authors.affiliation: Department of Pediatrics, Hospital Dr Roberto del Río, Faculty of Medicine, Universidad de Chile, Santiago, Chile. maab@mi.cl
authors.forename: María
authors.initials: M
authors.lastname: de los Angeles Avaria
authors.forename: Karin
authors.initials: K
authors.lastname: Kleinsteuber
authors.forename: Fernando
authors.initials: F
authors.lastname: Novoa
authors.forename: Paola
authors.initials: P
authors.lastname: Faundez
authors.forename: Pilar
authors.initials: P
authors.lastname: Carvallo
mesh_terms: D000293:Adolescent; D005260:Female; D006801:Humans; D009157:Myasthenia Gravis / Q000150:complications*; D009223:Myotonic Dystrophy / Q000150:complications* / Q000235:genetics*; D065636:Myotonin-Protein Kinase; D010375:Pedigree; D017346:Protein Serine-Threonine Kinases / Q000235:genetics
chemical_list: C585517:DMPK protein, human; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases