Case report Sarcoidosis in a case of MuSK-positive myasthenia gravis Konstantinos Spengos * , Sofia Vassilopoulou, Yiolanda Christou, Panagiota Manta Neuromuscular Unit of the Department of Neurology, Eginition Hospital, University of Athens School of Medicine, Vas. Sofias 72, 11528 Athens, Greece Received 7 April 2008; received in revised form 10 June 2008; accepted 10 July 2008 Abstract Whereas the coexistence of different autoimmune or rheumatologic diseases with myasthenia gravis is well documented, the combination of myasthenia with sarcoidosis is extremely rare. There very few case reports of patients suffering from these two immune-mediated diseases. Nearly all had acetylcholine receptor antibodies. As far as we know myasthenia gravis with antibodies to muscle-specific tyrosine kinase–MuSK–has not been associated with any form of sarcoidosis. We present probably the first case of MuSK-positive myasthenia gravis with concurrent, asymptomatic pulmonary sarcoidosis. Ó 2008 Published by Elsevier B.V. Keywords: MuSK antibody positive myasthenia gravis; Sarcoidosis 1. Introduction The coexistence of different autoimmune diseases in certain patients is well known. Epidemiological studies and several case series have demonstrated an increased incidence of autoimmune disorders, such as autoimmune thyroid and dermatologic diseases and systemic disorders, such as lupus erythematosus and rheumatoid arthritis in patients with myasthenia gravis (MG) [1,2]. However, the combination of MG and sarcoidosis seems to be very rare [3–8]. In some cases MG came first, while in others sarcoidosis was already diagnosed when myasthenic features began. However, most of these cases of MG were characterized by the presence of acetylcholine receptor anti- bodies (AChR-Ab). To our knowledge MG with antibodies to muscle-specific tyrosine kinase (MuSK-Ab) has not been associated with any form of sarcoidosis. We present the probably first-ever case of a MuSK-Ab positive MG with concurrent, asymptomatic pulmonary sarcoidosis. 2. Case report A 70-year-old Caucasian man presented in our outpatients’ clinic with a two-year history of slowly progressive difficulties when climbing stairs and walking down-hill. Fluctuating episodes of ptosis, dysarthria, swallowing difficulties and diplopia had also occurred during the preceding six months. Exaggeration of symptom intensity after exercise was also reported and documented on examination. The tensilon test was judged positive as ptosis and dysarthria resolved for a few minutes, shortly after intravenous edrophonium administration. Repetitive nerve stimulation before and after voluntary activation revealed a significant decrement in the compound muscle action potential of up to 34% in all the muscles examined. Further serological evaluation revealed no AChR-Antibodies, whereas MuSK-Ab titers were pathologically elevated (12.4 nM; normal <0.03 nM). Based on all the above-mentioned findings the diagnosis of MuSK-Ab positive MG was established. Oral administra- tion of pyridostigmine was then started leading to a significant improvement. However, the daily dosage had to be limited at 180 mg due to intensive drug induced side effects that have often been noted in MuSK-Ab positive MG [9]. Since no full symptom remission was achieved prednisone (40 mg daily) was added leading to further clinical improvement. 0960-8966/$ - see front matter Ó 2008 Published by Elsevier B.V. doi:10.1016/j.nmd.2008.07.001 * Corresponding author. Tel.: +30 210 7289290; fax: +30 210 7216474. E-mail address: konsatntinos.spengos@gmail.com (K. Spengos). www.elsevier.com/locate/nmd Neuromuscular Disorders 18 (2008) 890–891