Decreased capillary density in juvenile dermatomyositis and in mixed connective tissue disease

Objective, To assess whether quantitative capillary microscopy is a useful tool to evaluate capillary abnormalities in children with connective tissue diseases. Methods. Eight children with juvenile dermatomyositis (JDM), 6 with mixed connective tissue disease (MCTD) and 23 healthy children were investigated with computer based quantitative capillary microscopy. Median disease duration was 1 year among JDM (1-4) and 3 years (1-7) among MCTD. Results, Capillary density was decreased in JDM [median 2.5 (1.4-4.3) loops/mm (p < 0.001)] and in MCTD [median 5.0 (4.1-7.0) loops/mm (p < 0.05)] compared to healthy controls [median 6.8 (5.3-8.0) loops/mm]. Median capillary loop area was increased in JDM [median 8.5 (3.0-15.8) 10(-3) mm(2) (p < 0.001)] and in MCTD [median 4.5 (3.0-6.0) 10(-3) mm(2) (p < 0.02)] compared to controls [median 2.5 (1.0-4.0) 10(-3) mm2]. Conclusion, Quantitative nailfold capillary microscopy is a sensitive indicator of JDM. In MCTD this technique is less discriminative.