Nailfold capillary microscopy in connective tissue disease: a quantitative morphological analysis.

Photomicrographs were taken of front line nailfold capillary loops in 18 healthy women (controls) and 42 women with established connective tissue disease (14 rheumatoid arthritis, 19 systemic lupus erythematosus, nine scleroderma). Measurements were made of apex width, maximum limb and loop widths, capillary length, interpeak distance, and frequency per linear millimetre. A numerical index for assessing capillary dilatation was derived, based on the mean of the apex plus maximum limb widths. Results show considerable overlap in subject means. Statistical analysis showed no difference between rheumatoid arthritis and control groups. Patients with systemic lupus erythematosus had slightly larger loops at a lower frequency (not statistically significant); three patients with an abnormal capillary index also had high titres of ribonucleoprotein antibody. Six scleroderma patients had abnormal indices, two of whom had high titre ribonucleoprotein antibody. No relation between capillary morphology and clinical features was found.