Patient description: A previously healthy 8-year-old boy presents with a complaint of right lower extremity pain and fever. He reports limping for the past two days. The parents report no previous trauma, but do remember a tick bite during a summer visit to Maryland several months ago. They do not remember observing erythema migrans. On examination, the right knee is tender and swollen. Peripheral WBC count and SRP are slightly elevated.

Clinical trial eligibility criteria: eligible ages (years): 13.0-999.0,  Lyme Disease Screening Age greater than or equal to 13 years old Suspect of suffering from Lyme disease Post-Treatment Lyme Disease Syndrome (PTLDS): For the purposes of this study, PTLDS is defined as occurring in male or female patients age 13 and above who have been diagnosed with confirmed Lyme disease, have received recommended antibiotic therapy and have persistent or relapsing symptoms and/or signs for at least six months after therapy. They also should have no other documented explanation for their signs and symptoms and have positive serum antibodies to B.burgdorferi confirmed by Western blot according to the CDC (IgG immunoblot is considered positive if five of the following 10 bands are present: 18 kDa, 21 kDa (OspC), 28 kDa, 30 kDa, 39 kDa, 41 kDa (Fla), 45 kDa, 58 kDa (not GroEL), 66 kDa, and 93 kDa) Lyme arthritis controls: For the purposes of this study, Lyme arthritis is defined as occurring in an otherwise healthy male or female aged 18 and above who have intermittent episodes of arthritis involving one or few joint, without any other cause being documented, and have positive serum antibodies to B.burgdorferi confirmed by Western blot according to the CDC criteria Recovered Controls: For the purposes of this study, a recovered control is defined as an otherwise healthy male or female aged 18 and above who has had Lyme disease, fulfilling the CDC Lyme Disease National Surveillance Case Definition and who had received accepted antibiotic treatment for Lyme disease (at least 3 months since the end of antibiotic therapy before protocol evaluation) and who are currently asymptomatic Seropositive Controls: For the purposes of this study, a serpositive control is defined as an otherwise healthy male or female aged 18 and above who has positive serum IgG antibody to B.burgdorferi by Western blot according to the CDC and are asymptomatic and who recall no episodes of disease compatible with Lyme infection and have not received antibiotic therapy for Lyme disease OspA vaccinated control: For the purposes of this study, a OspA vaccinated control is defined as an otherwise healthy male or female aged 18 and above who has received at least two doses of the OspA vaccine for Lyme disease (Lymerix [R]). These controls may have a positive ELISA for B.burgdorferi but a negative (or unreadable) IgG western blot Multiple sclerosis controls: For the purposes of this study, a multiple sclerosis control is defined as an otherwise healthy male or female aged 18 and above with relapsing-remitting or progressive multiple sclerosis as defined by the Clinical Trial Committee of the National Multiple Sclerosis Society and no evidence of prior exposure to B.burgdorferi as indicate by negative history for Lyme disease and negative Western blot for B.burgdorferi in the serum by the CDC criteria. Patients should have a Kurtzke or Expanded Disability Status Scale (EDSS) between 1 to 5 Healthy Volunteers: For the purpose of this study, a healthy volunteer is defined as healthy male or female, age 18 and above, with no history compatible with acute or chronic Lyme disease and negative western blot to B.burgdorferi in the serum by the CDC criteria  General Age less than 18 (less than 13 for patients with chronic Lyme disease) Weight less than 70 Lb (35 kg) Pregnancy or lactation Women with childbearing potential who are sexually active and unwilling to use effective contraception Clinically significant laboratory abnormalities including positive test for syphilis (RPR), HBsAg, anti-HCV, anti-HIV Chronic medication use will be evaluated in a case-by-case basis Not able to understand all of the requirements of the study or unable to give informed consent and/or comply with all aspects of the evaluation FOR PTLDS AND LYME In addition to the general