A patient with serologically confirmed infection by Borrelia burgdorferi presenting with painful paresis and atrophy of the proximal muscles of both upper extremities and bilateral facial paresis is described. Electromyography showed a neurogenic and myopathic pattern, and creatine kinase was raised. Muscle biopsy revealed the typical signs of focal myositis. Treatment with i.v. penicillin led to dramatic clinical and serological improvement. Muscle biopsy was repeated 2 months later; neurogenic changes were still present, but no inflammatory signs could be seen anymore. Thus, the presented case may be the first reported of meningopolyneuritis accompanied by focal nodular myositis, in the second stage of Lyme borreliosis.