Cutaneous pseudolymphoma (CPL) is a reactive polyclonal T- or B-cell lymphoproliferative process. CPL may appear as localized or disseminated skin lesions. While most cases of CPL are idiopathic, they may also occur as a response to, for example, contact dermatitis, arthropod reactions, and bacterial infections. CPL can be classified based on its clinical features, but all variants have similar histopathological patterns of either predominantly B-cell infiltrates, T-cell infiltrates, or mixed T/B-cell infiltrates. The prognosis of CPL is good, but the underlying disease process should be taken into account. If an antigenic stimulus is identified, it should be removed. In patients with idiopathic CPL, a close follow-up control strategy should be adopted. The aim of this systematic review is to summarize all reported treatments for CPL. The review was based on articles from the PubMed database, using the query "skin pseudolymphoma treatment", English and German, about "human" subjects, and published between 1990 and 2015 documenting adequate treatment and/or aetiology. Mainly individual case reports and small case series were found. Treatment options include topical and intralesional agents, systemic agents, and physical modalities. The final part of the review proposes a treatment algorithm for CPL according to each aetiology, based on the literature of the last 25 years. Future research should focus on randomized controlled trials and studies on long-term outcomes, which were not identified in the current review.

SummaryNecrobiosis lipoidica (NL) is a rare granulomatous disease of hitherto unclear etiology frequently seen in patients with diabetes. Characterized by its potential for ulcerations, it often presents a serious burden for those affected. There are currently neither German nor European guidelines for the treatment of NL. At the same time, standard treatment with topical or intralesional corticosteroids does not always show satisfactory results. We therefore set out to evaluate whether the various treatment regimens published since 2000 have actually expanded the therapeutic armamentarium in a relevant manner. Included were all publications that described more than one patient being treated with any given therapeutic modality. Overall, we analyzed data for 16 different treatment regimens reported in 49 publications.The largest amount of data exists for topical PUVA therapy, photodynamic therapy (PDT), and systemic treatment with fumaric acid esters. Remarkably, our analysis showed that with an increase in the number of documented patients treated with a given therapeutic modality, the proportion of those achieving a complete or partial response actually decreased. This was interpreted as publication bias. Thus, no clear recommendation can be given for second-line therapy in case topical or intralesional corticosteroids fail.

Eosinophilic cellulitis is an inflammation of, until now, unknown etiology that was first described by George Wells in 1971. Its dominating histological hallmarks are so-called "flame figures" and an eosinophilic infiltrate. Here, we report the case of a 46-year-old man who initially presented with excoriated papules that were histologically interpreted as consistent with "arthropod reactions." Later on, the clinical presentation changed to erythematous plaques, partially with cockade-like aspects. At this time, new biopsies were performed showing a superficial and deep perivascular lymphocytic and heavily eosinophilic infiltrate and flame figures, thus allowing to establish the diagnosis of Wells' syndrome. Under treatment with oral prednisolone and dapsone, the patient showed a rapid improvement of the condition. The presented case demonstrates both the clinical and histopathologic life of lesions of Well's syndrome in the course of the disease from unspecific to distinctive. The need for repeated biopsies is discussed. Current understanding of the pathogenesis of Wells' syndrome and its correlating histological features are elucidated.

Summary Eosinophilic dermatoses are a heterogeneous group of diseases, characterized by an eosinophil‐rich infiltrate and/or degranulation of eosinophils. Blood eosinophilia may be an associated feature. Typical, albeit not specific histological findings include ‘flame figures’, which are caused by the accumulation of cationic proteins released by eosinophils and subsequent collagen denaturation. “Classic” eosinophilic dermatoses include eosinophilic cellulitis (Wells syndrome), granuloma faciale, eosinophilic fasciitis (Shulman syndrome) and eosinophilic folliculitis (Ofuji disease). In addition, there is a multitude of skin diseases that present with varying degrees of eosinophilic infiltration. These include atopic dermatitis, bullous pemphigoid, urticaria, allergic contact dermatitis, prurigo nodularis, arthropod bite reaction, parasitic infections, and drug hypersensitivity. Even though these disorders share a common characteristic (tissue eosinophilia), they differ greatly in their clinical presentation.

In general, there are only few studies investigating the histological features of factitious skin disorders. Another problem arises from the fact that, even if clinical and histological findings are suggestive of dermatitis artefacta, subsequent confirmation of the exact mechanism of injury is frequently not possible, thus leaving room for speculation. This complicates defining specific histological patterns based on the various types of injuries. Overall, the results of the present study suggest that a factitious disorder should be considered if histological findings include blistering with a mild inflammatory infiltrate, rupture of collagen fibers, multinucleated keratinocytes, or elongated and vertically aligned keratinocytic nuclei.