[30-year-old Patient with suspected Marfan Syndrome and Progressive Gait disturbance].

History A 30-year-old man presented with a history of progressive muscle weakness, difficulty in concentrating, and a slender habitus since early childhood. Marfan syndrome was suspected since the age of 14. Examinations 13 years later he was examined by Marfan experts and by genetic testing and Marfan syndrome could not be confirmed. Further neurological examination revealed the suspected diagnosis of myotonic dystrophy type 1, which was confirmed by genetic testing. Treatment and course Similar to Marfan syndrome, myotonic dystrophy is a multisystemic disorder with the risk of cardiac arrythmias. It is necessary to provide an interdisciplinary care by neurologists, internists, ophthalmologists, speech therapists, and physiotherapists. Conclusion It is not enough to take the habitus as the principle sign to diagnose Marfan syndrome. Furthermore, it is essential to consider symptoms that are not typical for Marfan syndrome, such as cognitive deficiencies or progressive paresis.