Another Great Imitator: Allergic Contact Dermatitis Differential Diagnosis, Clues to Diagnosis, Histopathology, and Treatment

Mimics of Dermatitis

Dermatitis is a common condition frequently encountered by dermatologists. The diagnosis of dermatitis can be challenging because this condition is often multifactorial, and many skin diseases that can mimic dermatitis should be considered in the differential diagnosis. It is important to recognize and be familiar with these conditions because some of them can represent signs of systemic disease or malignancies and misdiagnosis can lead to mismanagement and adverse outcomes for the patient.

Patch Test Clinic Start-up: From Basics to Pearls

Allergic contact dermatitis is a prevalent burdensome condition affecting millions of Americans. Patch testing, the criterion-standard allergic contact dermatitis diagnostic tool, is underused by US dermatologists. Incorporating patch testing into modern dermatology practices is achievable with utilization of accurate resources and sustainable support. This review focuses on the basics of patch testing and provides practical pearls to assist novice providers in establishing a contact dermatitis specialty practice.

Protein Causes of Urticaria and Dermatitis

Protein contact dermatitis is a cutaneous hypersensitivity reaction after chronic, recurrent exposure or chronic irritation to animal or plant protein. Although the pathophysiological mechanisms underlying protein contact dermatitis are not well characterized, protein contact dermatitis is thought to be caused by combined type I/IV-mediated, type-1 mediated, or a Langerhans cell immunoglobulin E-mediated delayed hypersensitivity reaction. This chapter reviews the epidemiology, pathogenesis, clinical features, common protein allergens, diagnostic process, treatment options, and prognosis of protein contact dermatitis.

Allergic Contact Dermatitis and Concomitant Dermatologic Diseases: A Retrospective Study

BACKGROUND

Allergic contact dermatitis (ACD) can exist in the setting of other dermatologic conditions. It is known that the treatment of these conditions can cause ACD, increasing both diagnostic and treatment difficulty.

OBJECTIVE

The aim of this study was to determine the frequency of common dermatologic conditions in the setting of ACD and in specific patient populations.

METHODS

A retrospective database study was completed using Truven Health to collect information on patch-tested ACD patients. Demographics and diagnostic information were retrieved. Of those with ACD, the presence of 15 dermatologic diagnoses was investigated. Subanalyses were conducted for each condition, including International Classification of Diseases, 10th Revision code specificity, demographics, and diagnostic information.

RESULTS

A total of 6380 patients (76.83% female) were given a diagnosis of ACD via patch testing. Of those with concomitant disease, those most common include atopic dermatitis (23.98%), urticaria (16.69%), and acne (11.51%). Eight of the concomitant conditions were found to have statistical significance in comparing the average age of ACD diagnosis with the selected diagnoses (α = 0.05).

CONCLUSIONS

Common dermatologic diseases can exist concomitantly with ACD, many of which can be treated by compounds that precipitate or worsen preexisting ACD. The average age of the diagnosis varies from concomitant diagnoses, which can contribute to difficulty in ACD diagnosis and treatment.

Adverse cutaneous reactions to chemotherapeutic drugs

Drug reactions resulting from chemotherapy agents are common and frequently affect the skin. Although often benign, a select few of these cutaneous reactions may necessitate immediate changes to the antineoplastic regimens. Given the diversity of chemotherapeutic skin reactions and their complex implications on patient management, an organized conceptual schema is imperative for proper patient care. We evaluate a number of commonly seen chemotherapy-induced skin toxicities organized by pathogenic mechanism and drug class, providing a framework for the identification and categorization of adverse events to prevent unrecognition. Groupings of these reactions include direct cytotoxicity and/or drug accumulation, immunologic hypersensitivity, and aberrant molecular signaling.

Clinical and histopathological characterization of paradoxical head and neck erythema in patients with atopic dermatitis treated with dupilumab: a case series

Dupilumab is the first biologic registered for the treatment of atopic dermatitis (AD). We report on seven patients with AD presenting with a paradoxical head and neck erythema that appeared 10-39 weeks after the start of dupilumab treatment. The patients presented with a relatively sharply demarcated, patchy erythema in the head and neck area that showed no or less scaling compared with their usual eczema. Only one patient experienced symptoms of itch and burning, although this was notably different from his pre-existent facial AD. Except for a notable 'red face', eczema on other body parts had greatly improved in six of the seven patients, with a mean numerical rating scale for treatment satisfaction of 9 out of 10 at the time of biopsy. Treatment of the erythema with topical and systemic drugs was unsuccessful. Despite the presence of this erythema, none of our patients discontinued dupilumab treatment. Lesional skin biopsies showed an increased number of ectatic capillaries, and a perivascular lymphohistiocytic infiltration in all patients. In addition, epidermal hyperplasia with elongation of the rete ridges was observed in four patients, resembling a psoriasiform dermatitis. Additional immunohistochemical stainings revealed increased numbers of plasma cells, histiocytes and T lymphocytes. Interestingly, spongiosis was largely absent in all biopsies. We report on patients with AD treated with dupilumab developing a paradoxical erythema in a head and neck distribution. Both clinically and histopathologically we found a heterogeneous response, which was most suggestive of a drug-induced skin reaction.