CHICAGO – The big news regarding Lyme disease at the annual meeting of the American College of Rheumatology was a report that hamstring tendon calcification is extremely common among patients who have persistent Lyme arthritis despite having undergone appropriate antibiotic therapy.
“This is a fascinating study,”, a Lyme disease expert not involved in the research, said regarding the by , and her coworkers at Massachusetts General Hospital, Boston.
One implication of this finding by a renowned group of Lyme disease researchers is that persistent posttreatment Lyme arthritis may in many cases be due to ongoing immunostimulation by spirochete remains located in hamstring tendons, a privileged, relatively avascular site where the foreign material may be able to evade immune clearance.
Also, as Dr. Arvikar pointed out in her presentation, calcific tendinopathy implies prior inflammation or degenerative changes. Thus, these calcific hamstring abnormalities implicate the hamstring tendons as a potential initial site of infection by hematogenously-spread Borrelia burgdorferi during the prearthritis phase of Lyme disease.
A further implication of the study is the possibility that hamstring tendon calcification could serve as a useful diagnostic aid in distinguishing Lyme arthritis from arthritis due to other causes. In the study, hamstring calcific tendinopathy was found in 28 of 31 adults and children with Lyme arthritis, 3 of 22 with knee osteoarthritis, and 1 of 14 patients with inflammatory arthritis, Dr. Arvikar noted.
She and her coinvestigators evaluated tendon pathology in their retrospective study of patients at the Massachusetts General Hospital Rheumatology Musculoskeletal Ultrasound Clinic. They used ultrasound because they have found it offers far better spatial resolution of calcification than does MRI or x-rays. The semimembranosus tendon was the hamstring tendon that most commonly exhibited calcification, although 11 patients with Lyme arthritis also had involvement of the semitendinosus tendon, compared with none of the controls with osteoarthritis or inflammatory arthritis.
In the eight patients with serial ultrasound evaluations over a period of up to 12 months, the calcification persisted but the symptoms of tendinitis and synovitis improved.