DELTOID MUSCLE IN PATIENTS WITH POLYMYALGIA-RHEUMATICA

Objective. To investigate muscle tissue in patients with polymyalgia r heumatica (PMR). Methods. Deltoid muscle biopsies obtained from 10 fem ale patients with PMR before corticosteroid therapy and from 5 healthy female controls of similar age were studied using light microscopy. S erial cryosections were stained for the activity of myofibrillar ATPas es at various pH and for oxidative and glycolytic enzymes. Sections we re also incubated with antibodies against different myosin heavy chain (MyHC) isoforms, and the laminin al chain, identifying capillaries an d cell borders, and against ligands for selected adhesion molecules. R esults. The muscle fibers in patients and controls were mainly of type I containing slow MyHC, or type II AB containing both fast A and fast B MyHC isoforms. The oxidative capacity of the muscle fibers was in g eneral low. In the patients with PMR the numbers of capillaries per un it area of type I and type II fibers were higher than in controls (p = 0.05 and p < 0.5, respectively). No accumulation of inflammatory cell s or increased expression of adhesion molecules in the muscle sections from patients with PMR was found. Conclusion. There is increased micr ovascularization of the deltoid muscle fibers in patients with PMR. Wh ether this is directly associated with the systemic inflammation and t he musculoskeletal symptoms or is mainly due to muscle fiber atrophy c ould not be determined.