Femoral mononeuropathy in Lyme disease: a case report

Peripheral neuropathy is a common complication of Lyme disease. Cranial mononeuropathy, particularly that affecting the facial nerve, can be a presenting symptom, and at times, it can be associated with polyradiculopathies or plexopathies. However, isolated femoral neuropathy has not yet been reported in Lyme disease; therefore, we felt the need to present this case. Laboratory investigations were performed on a 67-year-old man living in a region at high risk for Lyme disease after he developed erythema migrans on his chest, accompanied by the swelling of his left knee joint. A Western blot immunoglobulin assay was performed, including a screening for connective tissue disorders. Positive serological test results led to the administration of oral doxycycline therapy at a dosage of 100 mg twice daily. Shortly afterwards, he developed gait difficulties and frequent falls. The clinical examination and electrodiagnostic studies were consistent with femoral neuropathy. To look for etiologies other than Lyme disease, radiographic studies of his lumbar spine, pelvic cavity, retroperitoneal compartment, and hips were conducted. In addition, he was screened for diabetes. However, no other etiologies were found to explain the femoral neuropathy. Eventually, he recovered, and he was able to return to work. We firmly believe that the femoral neuropathy and Lyme disease seen in this patient were causally related.