Histologic features of granulomatous skin diseases. Part 1: Non-infectious granulomatous disorders

Therapie des nekrobiotischen Xanthogranuloms - Fallserie und aktuelle Literatur: Therapy of necrobiotic xanthogranuloma - case series and review of the literature

Das nekrobiotische Xanthogranulom ist eine seltene Erkrankung, die zu den Nicht‐Langerhans‐Zell‐Histiozytosen gehört. Charakteristisch sind gelbliche Hautveränderungen, die typischerweise periorbital lokalisiert sind. Extrakutane Manifestationen aller Organe sind möglich und können potenziell lebensbedrohliche Komplikationen verursachen. Die Erkrankung gehört zu den fakultativen Paraneoplasien und zeigt eine hohe Assoziation zu Paraproteinämien. Diese Aspekte sollten in der Umfelddiagnostik berücksichtigt werden. Da die Erkrankung sehr selten ist, gibt es bislang keine standardisierten Richtlinien zur Therapie. Als erfolgreiche Therapieregime haben sich insbesondere die Kombination aus Prednisolon und Chlorambucil sowie die intravenösen Immunglobuline herausgestellt. Wir präsentieren vier Fälle aus unserer Klinik sowie die aktuellen Ergebnisse der Literatur in diesem Mini‐Review und möchten damit die therapeutische Herausforderung sowie die Relevanz der Erarbeitung von Richtlinien unterstreichen.

Therapy of necrobiotic xanthogranuloma - case series and review of the literature

Necrobiotic xanthogranuloma is a rare disease that is part of the non-Langerhans cell histiocytoses. It is characterized by yellowish skin lesions, which are typically periorbitally localized. Extracutaneous manifestations of all organs are possible and can cause potentially life-threatening complications. The disease also belongs to the facultative paraneoplasias and is often associated with paraproteinemia. These aspects should be considered regarding further diagnostics. Due to the rarity of the disease, there are no standardized guidelines for therapy so far. The combination of prednisolone and chlorambucil as well as intravenous immunoglobulins seem to be effective therapeutic options. We present four cases from our clinic as well as the current results of the literature in this mini-review and would like to highlight the therapeutic challenge as well as the need for the development of guidelines.

Ring-shaped plaque on the face

Granulomatosis Miescher is a very rare, chronic, granulomatous (non-necrobiotic) disease. Clinical characteristics are a slowly centrifugally growing brownish plaques with partly yellowish parts and telangiectasias. Histology shows perivascular epithelioid cell granulomas with few giant cells and only isolated necrobiosis lesions.

Dermatoscopy of Cutaneous Granulomatous Disorders

Cutaneous granulomatous disorders represent diseases with underlying granulomas on histology and are broadly divided into infectious and noninfectious disorders. Although histology is sine qua non in diagnosis of granulomatous disorders, lately dermoscopy has come up as a useful tool assisting in diagnosis of granulomatous disorder. Dermoscopy of granulomatous disorder is characterized by localized or diffuse, structureless yellowish-orange areas, along with vessels. Dermoscopic features of granulomatous disorders can be overlapping among various disorders, but detailed accurate assessment of various findings and their pattern may be useful in differentiating among them. In addition to this, peculiar dermatoscopic findings seen can also prove useful in distinguishing between various disorders. Hereby, we discuss dermatoscopic findings of various granulomatous disorders.

Non-infectious granulomatous dermatoses

Granulomatous dermatoses comprise a wide range of etiologically and clinically distinct skin diseases that share a common histology characterized by the accumulation of histiocytes include macrophages. While the pathogenesis of these disorders is not fully understood, the underlying mechanism is thought to involve a reaction pattern caused by an immunogenic stimulus. Antigen-presenting cells and the effect of various cytokines play a key role. Our understanding of granulomatous reaction patterns has been advanced by insights drawn from observations of such reactions in patients on immunomodulatory therapy and in individuals with genetic immunodeficiency. Traditionally, a distinction is made between infectious and non-infectious granulomatous dermatoses. The present CME article addresses granulomatous skin diseases for which there is no evidence of a causative infectious agent. Common representatives include granuloma annulare, necrobiosis lipoidica and cutaneous sarcoidosis. Granulomatous dermatoses may be part of the clinical spectrum of various systemic disorders or may be associated therewith. Some neoplastic disorders may mimic granulomatous dermatoses histologically. Given the pathogenetic diversity involved, the clinical presentation, too, is quite varied. Overall, however, each disorder is characterized by typical clinical features. The diagnosis always requires thorough clinicopathologic correlation. Treatment is preferably based on the underlying pathogenesis and frequently involves anti-inflammatory agents. In most cases, however, there is insufficient study data. The dermal nature of these disorders frequently poses a therapeutic challenge, especially with respect to topical treatment.

[Granulomatous reaction pattern of the skin : Interstitial granulomatous dermatitis - lymphoma - vasculitis]

A particular diagnostic situation in the classification of a granulomatous dermatitis results when no circumscribed granulomas but instead a diffuse interstitial histiocytic inflammatory infiltrate, a granulomatous vasculitis or a neoplastic lymphocytic infiltrate is found. Interstitial granulomatous dermatitis was originally described in patients with arthritis. Later, it was recognized that there are also associations with other usually immunological diseases. Differentiating between interstitial granulomatous dermatitis and the interstitial form of granuloma annulare, early morphea and variants of borreliosis or scleromyxedema as well as interstitial granulomatous drug reaction can be very difficult. In long-standing cutaneous granulomatous infiltrates, T‑cell lymphoma should be excluded. Occasionally only a small number of atypical lymphocytes can be found. The detection of a monoclonal T‑cell expansion is then particularly helpful. Only recently, a CD8-positive granulomatous cutaneous T‑cell lymphoma was described which occurred in patients with immunodeficiencies. A granulomatous vasculitis in the skin is extremely rare. According to the Chapel Hill classification from 2012, systemic granulomatous vasculitis is equated with giant cell arteritis. Extracutaneous large arteries are involved. On rare occasions, involvement of the temporal artery can result in skin necrosis. More commonly granulomatous infiltrates in combination with vasculitis can be observed, whereby various infectious diseases, sarcoidosis and nodular vasculitis should be considered. Granulomatosis with polyangiitis (formerly Wegener's granulomatosis), presents in the skin as leukocytoclastic vasculitis. Here granulomas are extremely rare.

[Differential diagnosis of granulomatous diseases]

Despite advances in the understanding of the pathophysiology, granulomatous diseases remain a diagnostic challenge for the clinician as well as for the pathologist. However, establishing the correct diagnosis of these diseases is a crucial prerequisite of targeted therapy. It is particularly essential to distinguish between an infectious and a non-infectious cause, since anti-infectious and anti-inflammatory or immunosuppressive approaches are opposing. Failure to establish the correct diagnosis can lead to adverse consequences for the patient. An interdisciplinary approach and a critical assessment of clinical, laboratory-chemical, microbiological, imaging, and anatomical-pathological findings are crucial for the evaluation of granulomatous disorders. This overview summarizes important landmarks and their value in the interplay of arriving at the correct diagnosis.

[Clinical and histological spectrum of palisaded granulomatous dermatitides : Granuloma annulare, necrobiosis lipoidica, rheumatoid nodules, and necrobiotic xanthogranuloma]

The palisading granulomatous dermatitides comprise a group of different skin diseases with similar histomorphologic forms of granuloma in the skin. Histopathologically characteristic are areas in the reticular dermis and subcutaneous fat with degenerated bundles of collagen surrounded by histiocytes and multinucleate giant cells aligned in a palisade (necrobiotic granuloma). Within the center of palisaded granulomas, mucin or fibrin can be found. The skin diseases presenting histologically with palisading granuloma are granuloma annulare and necrobiosis lipoidica. Palisading granuloma may also be an expression of systemic disease in rheumatoid nodules and necrobiotic xanthogranuloma. Little is known about the pathogenesis. The clinical presentation of the diseases is variable. Therapy is challenging and may not be satisfying.

[Non-infectious granulomatous inflammation: Focus on the lungs and skin]

Whereas a granulomatous reaction represents a physiologically useful immune defense mechanism against many infections, in autoimmune diseases granuloma formation and the concomitant inflammatory mechanisms may provoke a potentially organ-threatening reaction. Morphologically, several defined sub-types of granuloma have long been known, e.g. foreign body granuloma, tuberculous granuloma,sarcoid, pseudosarcoid, rheumatoid and rheumatic fever granulomas. However, in practice, assigning granulomas to a certain etiology from a biopsy or resection specimen can be a challenging diagnostic process. This article gives a practically oriented overview of the clinically most relevant non-infectious granulomatous diseases. The etiology, epidemiology, clinical correlation and morphology of granulomatous diseases are discussed, focussing on the lungs and skin.