Reumatol Clin. 2015;11(4):244–246 ww w . r eumatologiaclinica.org Case Report Dermatomyositis and Myasthenia Gravis: An Uncommon Association With Therapeutic Implications  Clara Sangüesa Gómez, Bryan Josué Flores Robles, Clara Méndez Perles, Carmen Barbadillo, Hildegarda Godoy, José Luis Andréu * Servicio de Reumatología, Hospital Puerta de Hierro-Majadahonda, Majadahonda, Madrid, Spain a r t i c l e i n f o Article history: Received 23 July 2014 Accepted 10 October 2014 Available online 21 January 2015 Keywords: Dermatomyositis Myasthenia gravis Inflammatory myopathies a b s t r a c t The association of dermatomyositis with myasthenia gravis (MG) is uncommon, having been reported so far in only 26 cases. We report the case of a 69 year-old man diagnosed with MG two years ago and currently treated with piridostigmyne. The patient developed acute proximal weakness, shoulder pain and elevated creatine-kinase (CK). He also developed generalized facial erythema and Gottron’s papules. Laboratory tests showed positive antinuclear and anti-Mi2 antibodies. Further analysis confirmed CK levels above 1000 U/l. The clinical management of the patient and the therapeutic implications derived from the coexistence of both entities are discussed. © 2014 Elsevier Espa ˜ na, S.L.U. All rights reserved. Dermatomiositis y miastenia gravis: una asociación infrecuente con implicaciones terapéuticas Palabras clave: Dermatomiositis Miastenia gravis Miopatías inflamatorias r e s u m e n La asociación de dermatomiositis y miastenia gravis (MG) es infrecuente, habiéndose comunicado hasta la actualidad únicamente 26 casos. Se presenta el caso de un varón de 69 a˜ nos diagnosticado de MG 2 a˜ nos atrás, en tratamiento con piridostigmina, que inicia cuadro agudo de debilidad muscular proximal, artralgias en hombros y elevación de creatincinasa (CK); así como aparición de eritema facial generalizado y pápulas de Gottron. En el estudio de laboratorio se evidenció positividad de anticuerpos antinucleares y anti-Mi2. Ulteriores determinaciones de CK mostraron niveles por encima de 1.000 U/l. Se discute el manejo clínico de este paciente y las implicaciones terapéuticas que plantea la coexistencia de ambas entidades. © 2014 Elsevier Espa ˜ na, S.L.U. Todos los derechos reservados. Introduction Idiopathic inflammatory myopathies (IIM), including der- matomyositis (DM), are a heterogeneous group of systemic autoimmune diseases whose main clinical feature is predomi- nantly proximal muscle weakness. 1 They are rare diseases, with an estimated annual incidence of 6 cases/10 5 individuals 2 and may be associated with other autoimmune diseases such as lupus or Sjogren’s syndrome.  Please cite this article as: Sangüesa Gómez C, Flores Robles BJ, Méndez Perles C, Barbadillo C, Godoy H, Andréu JL. Dermatomiositis y miastenia gravis: una asociación infrecuente con implicaciones terapéuticas. Reumatol Clin. 2015;11:244–246. * Corresponding author. E-mail address: jlandreu@arrakis.es (J.L. Andréu). Another autoimmune disease that causes muscle weak- ness, myasthenia gravis (MG), can also be associated with the IIM. 3–9 MG is rare, with an estimated prevalence of 140 cases/ 10 6 inhabitants. 10 Its pathogenesis derives from the compromise resulting from the binding of autoantibodies to proteins involved in the neuromuscular transmission signaling. Recognizing the association between the two entities is important due to its therapeutic implications. We present a case of DM in a patient previously diagnosed with MG. Clinical Case The patient was a 69 year-old-male Caucasian, diagnosed two years prior with MG, positive to anti-AChR antibodies and treated with pyridostigmine (60 mg/8 h). He was referred to our center due to the appearance of weakness which appeared a month 2173-5743/© 2014 Elsevier Espa ˜ na, S.L.U. All rights reserved.