[Unusual muscular involvement in ankylosing spondylitis].

Muscle involvement in ankylosing spondylitis has been little studied. The authors report two cases with marked muscular atrophy and functional impotence, which had directed the diagnosis towards a myopathy over a period of several years in the first case, and a suspected primary muscular disease associated with ankylosing spondylitis in the second. Muscle biopsies eliminated the diagnosis of myopathy in both cases, with rapid functional recovery with proper treatment. Following a review of the literature, two hypotheses can be considered to explain the muscular involvement in ankylosing spondylitis: one mechanism which appears well-established is a radiculitis with involvement of the paravertebral muscles: other authors suggest that there is nonspecific, generalized muscular involvement in this disorder.