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Pemphigus defines a group of blistering diseases characterized by autoimmunity against intraepidermal adhesion proteins and subsequent flaccid blister formation, two major subtypes of which are pemphigus foliaceus (PF) and pemphigus vulgaris (PV). Of these, PF is typically more benign and characterized by IgG autoantibodies against desmoglein-1 (DSG-1) with exclusive cutaneous involvement. In contrast, PV is typically more severe and characterized by IgG autoantibodies against desmoglein-3 (DSG-3) in the mucosal predominant form and against both DSG-3 and DSG-1 in the mucocutaneous form 1 .July 2017 Volume I Issue I Copyright 2017 The National Society for Cutaneous MedicineThe phenotypic expression of pemphigus subtypes is mediated by differences in desmoglein (DSG) autoantibody profiles, a concept that is demonstrated in rare cases of transition between pemphigus subtypes. Diagnosis of transition is made on the basis of changes in classic phenotypic expression in conjugation with changes in immunofluorescence and/or antidesmoglein ELISA.We report a 54-year-old male with a history of severe mucocutaenous pemphigus vulgaris (PV) brought into remission by treatment with systemic steroids and adjuvant rituximab infusions who re-presented approximately 1 year following steroid discontinuation with new crusted erosions covering the upper trunk and proximal extremities and notable absence of mucosal involvement. Antidesmoglein ELISA profile revealed an isolated rise in DSG-1 antibodies. Previous antidesmoglein ELISA profiles showed dual elevation in both DSG-1 and DSG-3 antibodies during active PV and absence of both DSG-1 and DSG-3 during disease remission.The current case describes a rare transition from PV to pemphigus foliaceus (PF) following rituximab therapy as suspected clinically by classic phenotypic expression and confirmed serologically by antidesmoglein ELISA. This is only the second reported case of pemphigus transition following rituximab adjuvant therapy, and there are less than thirty cases of PV to PF transition reported in the literature. There is currently not a satisfactory explanation for the autoantibody shifting that is observed in transition between pemphigus types. ABSTRACT INTRODUCTION

Extraskeletal osteosarcoma (ESOS) is a rare variant of osteosarcoma that arises without attachment to the underlying skeleton. These cancers are typically found embedded in deeper tissues, most commonly the muscle or fascia, and are rarely found within the skin or subcutis. Most tumors are large in size upon initial presentation, and carry a poor prognosis. We discuss the case of a 48-year-old Caucasian woman who presented to a dermatology clinic with an asymptomatic, small, mobile, subcutaneous mass that appeared clinically benign. After elective removal and histopathologic examination, the patient was diagnosed with ESOS. ESOS presenting in this manner is exceedingly rare, and this case highlights the importance of sending all excised specimens, even those with a benign presentation, for pathologic examination. K E Y W O R D Sdermatology, extraskeletal osteosarcoma, neoplasm, pathology, skin