[Characteristics of the rash in Mediterranean boutonneuse fever]

The typical papulomacular picture of boutonneuse fever is described. A series of atypical exanthemas is presented: simply erythemato-macular and typhus-like, nodular, vesicular. Skin biopsies showing the endothelial, thrombotic and parietal aspects of periadventitial infiltration (this being sometimes moderately and extensively pericapillary) are also presented. The reason for the absence of extensive thrombisation in extensive, marked rickettsiotic endothelitis are discussed, and stress is laid to the hitherto little-discussed, but significant involvement of dermal collagen.