When mycosis fungoides seems not to be within the spectrum of clinical and histopathological differential diagnoses

The most prevalent primary cutaneous T-cell lymphoma, mycosis fungoides (MF), is characterized by the development of plaques and nodules after an erythematous patchy phase that is non-specific. An infiltrate of atypical small- to medium-sized cerebriform lymphocytes in the superficial dermis, with variable epidermotropism, is the histopathological hallmark of the disease. In more advanced stages of the illness, large-cell transformation may be seen. Early diagnosis of MF can be very challenging based only on histopathologic or clinical findings, so it is critical to have a clinical-pathological correlation. Many atypical variants of MF that deviate from the classic Alibert-Bazin presentation of the disease have been described over the past 30 years, sometimes with different prognostic and therapeutic implications. Clinically or histopathologically, they can mimic a wide range of benign inflammatory skin disorders. To make a conclusive diagnosis in these cases, it is recommended to take multiple biopsies from various lesions and to carefully correlate the clinical and pathological findings. We have outlined the various facets of the illness in this review, positioning MF as a “great imitator”, with an emphasis on the more recently identified variations, differential diagnosis, and its benign mimics

Autoimmune bullous dermatoses in cancer patients treated by immunotherapy: a literature review and Italian multicentric experience

Cutaneous immune-related adverse events are frequently associated with immune checkpoint inhibitors (ICIs) administration in cancer patients. In fact, these monoclonal antibodies bind the cytotoxic T-lymphocyte antigen-4 and programmed cell death-1/ligand 1 leading to a non-specific activation of the immune system against both tumoral cells and self-antigens. The skin is the most frequently affected organ system appearing involved especially by inflammatory manifestations such as maculopapular, lichenoid, psoriatic, and eczematous eruptions. Although less common, ICI-induced autoimmune blistering diseases have also been reported, with an estimated overall incidence of less than 5%. Bullous pemphigoid-like eruption is the predominant phenotype, while lichen planus pemphigoides, pemphigus vulgaris, and mucous membrane pemphigoid have been described anecdotally. Overall, they have a wide range of clinical presentations and often overlap with each other leading to a delayed diagnosis. Achieving adequate control of skin toxicity in these cases often requires immunosuppressive systemic therapies and/or interruption of ICI treatment, presenting a therapeutic challenge in the context of cancer management. In this study, we present a case series from Italy based on a multicenter, retrospective, observational study, which included 45 patients treated with ICIs who developed ICI-induced bullous pemphigoid. In addition, we performed a comprehensive review to identify the cases reported in the literature on ICI-induced autoimmune bullous diseases. Several theories seeking their underlying pathogenesis have been reported and this work aims to better understand what is known so far on this issue

Blisters and Milia around the Peritoneal Dialysis Catheter: A Case of Localized Bullous Pemphigoid

We report on the appearance of multiple tense blisters surrounding the exit site of a Tenckhoff catheter in a 79-year-old woman with end-stage renal disease in peritoneal dialysis. The differential diagnoses included a contact allergic or irritative dermatitis to peritoneal dialysis catheter material and antiseptic agents, bacterial infection, and herpes virus infection, but milia were a clue for a subepidermal blistering disease and lead to appropriate investigations. The laboratory findings, the histopathological examination and the direct immunofluorescence assay confirmed the diagnosis of localized bullous pemphigoid. The disorder typically occurs in elderly people and may be related to drugs, hematological malignancies or neurological conditions but it can also be a complication of hemodialysis or peritoneal dialysis

Erosive pustular dermatosis of the scalp: A neutrophilic folliculitis within the spectrum of neutrophilic dermatoses: A clinicopathologic study of 30 cases

BACKGROUND: It is general opinion that histopathology is nonspecific and of little value in diagnosing erosive pustular dermatosis of the scalp (EPDS). OBJECTIVES: Clinicopathologic correlation of erosive pustular dermatosis of the scalp. METHODS: We reviewed the clinical and pathologic records of patients with a clinicopathologic diagnosis of EPDS between 2011 and 2016 at the Dermatopathology Unit of Turin University. RESULTS: Thirty elderly patients with EPDS were identified (22 men and 8 women). Androgenetic alopecia was present in 19 of 30 patients. Triggering factors included mechanical trauma in 10 of 30 cases, surgical procedures in 4 of 30 cases, and herpes zoster in 1 of 30 cases. Three patients were affected by autoimmune disorders. The vertex was the most common location. Disease presentation varied markedly from tiny, erosive, scaly lesions to crusted and hemorrhagic plaques, mimicking pustular pyoderma gangrenosum. The pathologic changes differed according to lesion type and disease duration. Interestingly, a spongiotic and suppurative infundibulo-folliculitis was observed in 8 of 30 cases. LIMITATIONS: This was a retrospective study. CONCLUSIONS: We believe that the primary lesion of erosive pustular dermatosis of the scalp is a spongiotic, pustular superficial folliculitis. The clinicopathologic similarities with other neutrophilic dermatoses, such as pustular pyoderma gangrenosum, suggest this condition should be included in this spectrum, where pathergy plays a pathogenetic role. Copyright © 2018 American Academy of Dermatology, Inc. Published by Elsevier Inc. All rights reserved

Invisible dermatoses: clues and pitfalls to diagnosis

The phrase “invisible dermatoses” has been used in two different contexts: 1) Invisible dermatoses to the clinician, i.e., skin diseases with no significant clinical features, 2) invisible dermatoses to the pathologist, i.e., clinical evident skin diseases that show subtle or hidden histological features resembling normal skin. The list of such diseases, originally comprising only few entities, has been gradually expanded over decades and now is a large one. This paper will focus on entities that fall into this category of subtle or “invisible” dermatoses histopathologically and offers to the dermatopathologist a strategy for their diagnosis, based mainly on proper awareness, recognition of subtle features, liberal use of special stains, immunofluorescence and immunohistochemistry and proper clinicopathologic correlation. The presentation of a series of “invisible dermatoses” will hopefully familiarize the reader with the diagnostic problems and pitfalls associated with and unique to the interpretation of biopsies from this category o

Atypical exanthem with acral involvement in adult patients associated with human herpesvirus 7 active replication: A case series

An "atypical exanthem" (AE) is an eruptive skin eruption that differs in morphology and etiology from classical exanthems and is often a reason for urgent medical evaluation. The most frequent cause of AEs is a viral infection, but an accurate etiology cannot be established basing on the sole clinical features. Human herpesviruses (HHV) have been often suspected as etiologic agents or cofactors in atypical rashes. We performed a retrospective analysis of adult patients presenting an atypical exanthem associated with HHV-7 active replication in our center. The charts of patients were reviewed and the demographic, clinical and laboratory data collected. Nine patients (six males and three females) were included in the study, with a mean age of 43 years for men and of 26 years for women. All patients presented active HHV-7 replication in plasma during the rash, which turned negative after the exanthem resolved. The exanthem displayed a maculopapular pattern involving the trunk, limbs and, notably, the acral regions, in six patients. In three cases the exanthem was confined to only the acral sites. In most cases, there was no fever and the inflammatory indices remained unchanged. Antihistamines, topical and systemic corticosteroids were used as treatment, with excellent symptom control. We propose adding skin manifestation associated with HHV-7 to the concept of atypical exanthems, in particular those localized to the acral regions