Microcirculation in ankylosing spondylitis

It was interesting to read the paper by Beauvais et al reporting two cases of ankylosing spondylitis (AS) with cutaneous vasculitis and IgA nephropathy' emphasising the possibility of vascular involvement in AS. We wish to emphasise this aspect by the evaluation of microcirculation in AS using nailfold capillaroscopy.2 Forty six patients were enrolled in this prospective study, divided into 32 AS patients (fulfilling the revised New York criteria,3 mean age 38 years. Twenty eight were HLA B27 positive, and there were 14 control patients (disc herniation) mean age 34-6 years. Capillaroscopic findings evaluated by the same investigator (JCR) (unaware of the diagnosis in most of the cases) were classified into five groups:4 normal; minor dystrophia (characterised by more than 15% tortuosity); oedema (recognised by fuzziness of pericapillar environment); microangiopathy (this pattern associates-a qualitative element represented by major dystrophies like megacapillaries with irregular diameter, tortuous meandering or bushy capillaries-and quantitative element (reduction of loop number in the nailfold distal row less than 9 per mm), and stasis (characterised by a dark blood flow, sometimes granular, with low speed and regular enlargement of the two branches). Statistical analysis used Fisher's exact test for normal and minor dystrophies on the one hand, and oedema and microangiopathy on the other. The results, summarised in the table, show more frequent capillaroscopic abnormalities in the AS group compared with controls, for the oedema and microangiopathy patterns (p = 0 01), whereas there was no difference for minor dystrophies. No differences were found in terms of age, disease duration rheumatological and extra articular manifestations (skin, kidney, gut) or biological parameters (CRP, serum IgA) between AS patients with microangiopathy (n = 5) and AS patients with a normal capillaroscopy (n = 9). Nailfold capillaroscopy is a simple, non invasive and reproducible technique.2 In this study minor dystrophies are seen with the same prevalence in both groups. A specific capillaroscopic pattern of AS does not seem to exist. Conversely, this study shows an increase of abnormalities like pericapillar fuzziness (oedema) (due to an inflammatory reaction), and microangiopathy. These findings are in accordance with the reports of clinical vasculitis associated with AS, such as cutaneous microscopic vasculitis' 56 with renal or gut involvement, or large vessel vasculitis, Takayashu's arteritis7 8 or polyarteritis nodosa.9 1" Histological studies have also revealed the possibility of vascular involvement in AS, as well as in the skin,"1 12 with immune deposits'2 13 as in the kidney.'4 15 The significance of these capillaroscopic modifications remains to be clarified (none of our patients with capillaroscopic microangiopathy displayed extra articular manifestation) but the mechanism of such a microvascular involvement may be consistent with an immune complex disease'6 in AS.