Diabetes mellitus is a widespread endocrine disease with severe impact on health systems worldwide. Increased serum glucose causes damage to a wide range of cell types, including endothelial cells, neurons, and renal cells, but also keratinocytes and fibroblasts. Skin disorders can be found in about one third of all people with diabetes and frequently occur before the diagnosis, thus playing an important role in the initial recognition of underlying disease. Noninfectious as well as infectious diseases have been described as dermatologic manifestations of diabetes mellitus. Moreover, diabetic neuropathy and angiopathy may also affect the skin. Pruritus, necrobiosis lipoidica, scleredema adultorum of Buschke, and granuloma annulare are examples of frequent noninfectious skin diseases. Bacterial and fungal skin infections are more frequent in people with diabetes. Diabetic neuropathy and angiopathy are responsible for diabetic foot syndrome and diabetic dermopathy. Furthermore, antidiabetic therapies may provoke dermatologic adverse events. Treatment with insulin may evoke local reactions like lipohypertrophy, lipoatrophy and both instant and delayed type allergy. Erythema multiforme, leukocytoclastic vasculitis, drug eruptions, and photosensitivity have been described as adverse reactions to oral antidiabetics. The identification of lesions may be crucial for the first diagnosis and for proper therapy of diabetes.

No definitive recommendation of preferable treatment procedures can be made based on the analyzed literature. Randomized controlled trials are needed to offer patients an evidence-based therapy with high-quality standardized treatment regimens for PLCA.

Necrobiotic xanthogranuloma (NXG) is an uncommon non-Langerhans cell histiocytosis involving skin and extracutaneous tissues. The lesions are usually asymptomatic and commonly appear in the periorbital area. Paraproteinemia is closely associated with NXG and its pathogenesis remains unclear. NXG prognosis is poor with several treatments showing variable results. Treatment of monoclonal gammopathy with alkylating agents does not necessarily influence the activity of the skin disease and vice versa. The aim of this systematic review is to summarize all reported treatments of necrobiotic xanthogranuloma of the skin, with or without underlying malignant condition and based on articles from the PubMed database using the query 'necrobiotic xanthogranuloma treatment', both in English and German, about 'human' subjects and published between 1980 and 2014, documenting adequate treatment for NXG. Mainly individual case reports, small case series and retrospective studies were found. Treatment options include topical and systemic corticosteroids, thalidomide, high-dose intravenous immunoglobulin (IVIG), chlorambucil, cyclophosphamide, fludarabine, rituximab, melphalan, infliximab, interferon alpha, cladribine, hydroxychloroquine, azathioprine, methotrexate, laser therapy, radiotherapy, surgery, PUVA, plasmapheresis and extracorporeal photopheresis. Randomized controlled trials and studies on long-term outcomes after treatment were not found and are necessary to focus on in the future.

To offer patients with PK an evidence-based high-quality standardized therapy, randomized controlled trials are needed.

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