Collagenolytic (necrobiotic) granulomas: part 1 – the ‘blue’ granulomas

Abstract

A collagenolytic or necrobiotic non-infectious granuloma is one in which a granulomatous infiltrate develops around a central area of altered collagen and elastic fibers. The altered fibers lose their distinct boundaries and exhibit new staining patterns, becoming either more basophilic or eosinophilic. Within the area of altered collagen, there may be deposition of acellular substances such as mucin (blue) or fibrin (red), or there may be neutrophils with nuclear dust (blue), eosinophils (red), or flame figures (red). These color distinctions can be used as a simple algorithm for the diagnosis of collagenolytic granulomas, i.e. 'blue' granulomas vs. 'red' granulomas. Eight diagnoses are included within these two groupings, which are discussed in this two-part article. In this first part, the clinical presentation, pathogenesis, and histologic features of the 'blue' collagenolytic granulomas are discussed. These are the lesions of granuloma annulare, Wegener's granulomatosis, and rheumatoid vasculitis. In the subsequent half of this two-part series, the 'red' collagenolytic granulomas will be discussed; these are the lesions of necrobiosis lipoidica, necrobiotic xanthogranuloma, rheumatoid nodules, Churg-Strauss syndrome, and eosinophilic cellulitis (Well's syndrome).Lynch JM, Barrett TL. Collagenolytic (necrobiotic) granulomas: part 1 -the 'blue' granulomas.

Neutrophil clearance: when the party is over, clean-up begins

“…If enough disintegrate in a given locale, tissue liquefaction results in formation of a puss-filled abscess [1]. In other instances, failure of neutrophil removal results in the so-called “nuclear dust” characteristic of lesions of ANCA positive polyarteritis [73]. Significantly, autoimmunity is often associated with clearance defects, and in particular, the production of anti-neutrophil antibodies [18,67].…”

Cutaneous Vasculitis Update: Diagnostic Criteria, Classification, Epidemiology, Etiology, Pathogenesis, Evaluation and Prognosis

“…Fig. 56 Interface dermatitis associated with either a neutrophilic or lymphocytic small vessel vasculitis can be found in entities such as perniosis (chilblains) or CTD such as (Fig. [50][51][52][53][54] Extravascular granulomas exhibiting eosinophilic debris around degenerated collagen bundles due to tissue eosinophilia and flame figures (so-called red granuloma) are found in CSS, 55 whereas extravascular granulomas with basophilic debris (''blue'' granuloma due to mucin, neutrophilic nuclear dust) are found in WG and rheumatoid vasculitis.…”

A granuloma annulare case without annular lesion: A rare variant

“…Immune mechanisms which develop secondary to delayed type hypersensitivity are held responsible for the pathogenesis of GA. CD4 (+) Th1 lymphocytes which are in the lesions and which release TNF with gamma interferon enable macrophages to stay in the lesion area. TNF, elastas, collagenase and matrix metalloproteinases released by these macrophages cause collagen destruction [6][7][8]. While the role of immunological mechanisms is reported in the pathogenesis, vascular damage caused by nonimmunogenic mechanisms has also been reported to be effective.…”