Pemphigus is a group of rare autoimmune bullous dermatosis of stratified squamous epithelia characterized by the presence of IgG autoantibodies directed against epithelial desmosomal adhesion molecules. This leads to the disruption of the cell to cell adhesion, resulting in acantholysis and intraepidermal blisters of the skin and mucosal surfaces. 1 It has been noted anecdotally in several case reports that the prevalence of rheumatoid arthritis (RA) and pemphigus may be coexisted, however, the significance of the association remains elusive. 2,3 We conducted a systematic review and meta-analysis to assess the association between pemphigus and RA. The systematic review and meta-analysis were conducted and reported in accordance with the recommended PRISMA guidelines, 4 using Ovid Medline, PubMed, Cochrane Central Register of Controlled Trials (CCTR), Cochrane Database of Systematic Reviews (CDSR), ACP Journal Club, Database of Abstracts of Review of Effectiveness (DARE) and EMBASE from their dates of inception to 12th October 2020. We combined the terms "pemphigus foliaceus", "pemphigus vulgaris", or "pemphigus" combined with "rheumatoid arthritis", "acantholysis", as either key words or MeSH terms. Eligible studies were those comparing RA cases in pemphigus vs controls. Pemphigus cases included pemphigus vulgaris, pemphigus vegetans, pemphigus foliaceus, pemphigus erythematosus, and drug-induced pemphigus identified by clinical diagnosis with either direct or indirect immunofluorescence staining or enzyme-linked immunosorbent assay. Abstracts, conference presentations, case reports, reviews and studies without controls were excluded. Odds ratio (OR) was used in statisti-3 Note: 9-7, low risk of bias; 4-6, moderate risk of bias; 0-3, high risk of bias. a Newcastle-Ottawa Scale (NOS). 10
Cutaneous collision tumours are the co-existence of two tumours of different histopathological morphologies that coincide at the same or adjacent anatomical sites. A large scalp nodule excised from a 70 year-old man revealed a collision tumour composed of cells of squamous carcinoma (SCC) and malignant melanoma. Immunohistochemistry using dual staining for melanoma and squamous cell carcinoma demonstrated an unusual pattern; nests of melanoma cells surrounded by a layer of squamous carcinoma cells. The unique architecture observed in the case suggested a relationship between the two tumours.
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