Nailfold capillary abnormalities in childhood-onset systemic lupus erythematosus: a cross-sectional study compared with healthy controls

Objectives: For selection of high-risk systemic lupus erythematosus (SLE) patients it is necessary to obtain indicators of disease severity that predict disease damage. As in systemic sclerosis, nailfold capillary abnormalities could be such a biomarker in SLE. The primary objective of this cross-sectional study is to describe capillary abnormalities in childhood-onset SLE (cSLE) cohort (onset < 18 years) and compare them with matched healthy controls. The secondary objective is to correlate the observed capillary abnormalities with demographical variables in both cohorts and with disease-specific variables in cSLE patients.

Methods: Healthy controls were matched for ethnic background, age and gender. Videocapillaroscopy was performed in eight fingers with 2-4 images per finger. Quantitative and qualitative assessments of nailfold capillaroscopy images were performed according to the definitions of the EULAR study group on microcirculation in Rheumatic Diseases.

Results: Both groups (n = 41 cSLE-patients and n = 41 healthy controls) were comparable for ethnic background (p = 0.317). Counted per mm, cSLE-patients showed significantly more 'giants' (p = 0.032), 'abnormal capillary shapes' (p = 0.003), 'large capillary hemorrhages' (p < 0.001) and 'pericapillary extravasations' (p < 0.001). Combined 'abnormal capillary shapes and pericapillary extravasations' (in the same finger) were detected in 78% (32/41 patients). By qualitative analysis, 'microangiopathy' was detected in 68.3% (28/41) and a 'scleroderma pattern' in 17.1% (7/41) of the cSLE-patients (without scleroderma symptoms). The difference of percentage positive anti-RNP antibodies in the group with or without a scleroderma pattern was not significant (p = 0.089). The number of 'abnormal capillary shapes per mm' was significantly correlated with treatment-naivety. The number of 'large pathological hemorrhages per mm' was significantly correlated with SLEDAI score and presence of nephritis. Compared to healthy controls, 'pericapillary extravasations' were found in significantly higher numbers per mm (p < 0.001) as well as in percentage of patients (p < 0.001).

Conclusions: Our observations confirm that giants, abnormal capillary morphology and capillary hemorrhages are also observed in cSLE, as was already known for adults with SLE. Number of capillary hemorrhages in cSLE was significantly correlated with disease activity. A high frequency and total amount of "pericapillary extravasations" was observed in cSLE patients, possibly revealing a new subtype of capillary hemorrhage that might reflect endothelial damage in these pediatric patients.