[How to explore the microangiopathy of collagen diseases]

Numerous methods for the exploration of the microangiopathy of collagen disease exist, but their perspective differs as a function of their use to assist early diagnosis, to establish a prognosis, to provide follow-up data or to attempt better understanding of the mechanism of these affections. Progressive systemic sclerosis is a very suitable collagen disease with which to illustrate these methods, since in this affection the microangiopathy is frequent, diffuse, of early onset and also formally implicated in the pathogenic rank. Biopsy specimens provide details of morphologic anomalies of the microcirculation. Capillary changes have been demonstrated in muscle and the choroid but in clinical practice histology samples involve mainly the digital pulp, subungual fold and accessory salivary glands. Isotopic and fluorescent angiography are, on the contrary, in vivo methods for dynamic exploration of skin microcirculation, but the invasive nature of these methods is an obstacle to their repetition in a same patient and to follow-up of the microangiopathy. Non-invasive vascular explorations avoid this pitfall. Thermometry, thermography, digital plethysmography under hot and cold conditions, videomicroscopy of the nailbed, percutaneous PO2 and laser-doppler tests measure functional parameters, the hemodynamic significance of which require discussion. Capillaroscopy, mainly oriented towards the study of capillary morphologic changes, also allows, together with plethysmography, measurement of digital systolic pressure. Exploration of the microangiopathy of collagen disease requires a judicious combination of currently available morphologic and functional techniques which, far from being superimposable are on the contrary complementary.