|
Wegener’s granulomatosis: Wegener’s granulomatosis is manifested in patterns of inflammation and
repair. Much of the tissue response is non-specific with zones of necrosis alternating with areas of inflammation and repair. A prominent neutrophilic component in the absence of demonstrable organisms is a common
feature. The patterns, in such areas, take on the qualities of necrotizing, neutrophilic collagenosis. Regardless of the site of involvement; such a lesion has pyodermatous qualities. A second common feature is a
necrotizing angiitis; the features include thrombosis and necrosis and mixed inflammatory infiltrates. If, in addition, the infiltrates include a granulomatous component, the reaction begins to acquire specificity.
Finally, the presence of a zone of palisaded histiocytes at the periphery of zones of necrosis (with no demonstrable organisms) offers support for a diagnosis of Wegener’s granulomatosis (S15C3P1-1-6 ).
Pigmented purpuras: The pigmented purpuras have an identity at a clinicopathologic level. Attempts
have been made to discredit this category. It has been proposed that a variety of common inflammatory processes may masquerade as a pigmented purpura. In this approach, common inflammatory processes are predisposed
to the leakage of blood into the superficial portion of the dermis. The hemodynamics of the anatomic site, being different from those in most other anatomic sites, promotes the extravasation of red blood
cells. Most examples of pigmented purpuras are characterized by infiltrates that extend along the vascular plexus of the papillary dermis beyond the perivenular plexus of the upper portion of the reticular dermis.
This extension of the infiltrates has been characterized as “capillaritis.” The classic leukocytoclastic (and even the controversial lymphocytic) vasculitides usually are characterized by infiltrates that are
relatively confined to the perivenular plexus of the reticular dermis. Often the papillary dermis and the epidermis are relatively spared. The pigmented purpuras share with the dermatitides of the superficial
reactive unit of the skin the quality of inflammatory infiltrates along vascular structures of the papillary dermis. Commonly, the infiltrates involve the basal layer of the epidermis to produce variations of a
lichenoid reaction (the combination qualifies as a superficial lichenoid lymphocytic vasculitis) (S15C3P2-1-4).
|
