Muscle biopsy abnormalities in systemic lupus erythematosus: correlation with clinical and laboratory parameters.

OBJECTIVES: To investigate the incidence and significance of Type II fibre atrophy, vessel wall thickening, lymphocytic vasculitis and myositis in needle quadriceps muscle biopsies from patients with systemic lupus erythematosus (SLE) and their correlations with clinical and laboratory parameters.
METHODS: Needle quadriceps muscle biopsies from 55 patients with SLE and 26 controls were prospectively examined. Clinical and laboratory parameters recorded at the time of muscle biopsy included arthralgia, arthritis, myalgia, proximal weakness, vasculitic rashes, Schirmer test, ENA antibodies, ESR, serum creatine kinase (CK) and plasma C3 degradation products.
RESULTS: Abnormal muscle biopsies were significantly more frequent in patients with SLE compared with controls (P < 0.005). None of the controls had lymphocytic vasculitis and/or myositis. The difference in incidence between patients with SLE and controls for lymphocytic vasculitis was significant at P < 0.005. Due to the small number of SLE patients with myositis, the difference in incidence for this abnormal finding reached only P = 0.09. In the SLE patient group, lymphocytic vasculitis was associated with significantly higher ESR values (P = 0.007) and higher incidence of arthritis (P = 0.01); and appears to characterise a subset of patients with positive Schirmer tests, anti-Ro and/or anti-La antibodies. Raised serum CK was found to correspond with underlying myositis in patients with SLE and these patients also had an increased incidence of symptoms of proximal weakness and/or anti-RNP antibodies. In contrast, both Type II fibre atrophy and vessel wall thickening failed to correlate with any of the clinical and laboratory parameters studied and appear to be non-specific findings.
CONCLUSIONS: Abnormal muscle biopsies are common in patients with SLE and the presence of lymphocytic vasculitis and/or myositis signify pathology in these patients. Histopathological abnormalities in needle quadriceps muscle biopsies are further valuable parameters in the assessment of patients with SLE.