Lyme disease is sometimes part of the differential diagnosis for amyotrophic 
lateral sclerosis (ALS). Herein we report on 414 individuals with ALS at the 
Massachusetts General Hospital who underwent laboratory testing for Lyme 
disease. Twenty-four (5.8%) were seropositive, but only 4 (0.97%) had confirmed 
past immunoreactive infection. Two of these patients received ceftriaxone for 1 
month without clinical improvement. Lyme disease was rare in 414 patients with 
ALS and is not likely to be causative.