A 38-year-old woman comes to the urgent care clinic with a 2-day history of sore throat. It is associated with fever and cervical lymphadenopathy, but not rhinorrhea, sneezing, or coughing. On examination, erythema and edema involving the posterior pharynx and a purulent tonsillar exudate are present. Rapid bedside streptococcal antigen testing is positive, and the patient is started on oral penicillin V. She returns the following day with a pruritic skin rash that came on suddenly after starting the antibiotic. The skin lesions observed on physical examination are shown in the image below. What is the most likely finding on biopsy of these lesions?

Question

A 38-year-old woman comes to the urgent care clinic with a 2-day history of sore throat.  It is associated with fever and cervical lymphadenopathy, but not rhinorrhea, sneezing, or coughing.  On examination, erythema and edema involving the posterior pharynx and a purulent tonsillar exudate are present.  Rapid bedside streptococcal antigen testing is positive, and the patient is started on oral penicillin V.  She returns the following day with a pruritic skin rash that came on suddenly after starting the antibiotic.  The skin lesions observed on physical examination are shown in the image below.  What is the most likely finding on biopsy of these lesions?

Quizplus · Accepted Answer

Urticaria ("hives") is a common, transient hypersensitivity disorder characterized by intensely pruritic, raised, erythematous plaques (wheals) that arise suddenly and resolve over several hours. They are most often caused by IgE-mediated degranulation of mast cells. They can also be due to non-IgE-mediated degranulation (eg, opiates, radiocontrast agents, physical urticaria) or mast cell-independent mechanisms (eg, aspirin, hereditary angioneurotic edema). Urticaria is due to increased permeability of the microvasculature, leading to edema of the superficial dermis. Involvement of the deep dermis and subcutaneous tissue is termed angioedema. Biopsy is rarely required for diagnosis. Findings on histopathology would typically include a mixed inflammatory infiltrate (mononuclear cells, neutrophils, and eosinophils) surrounding superficial dermal venules. Lymphatic channels may be engorged with transudative fluid. The overlying epidermis typically appears normal. (Choice A) Acantholysis is the loss of cohesion between keratinocytes in the epidermis. It is a characteristic finding in the pemphigus family of disorders. (Choice B) Acanthosis is a diffuse increase in thickness of the stratum spinosum (prickle cell layer) between the granular cell layer and the basal layer of the epidermis. Common conditions displaying acanthosis include psoriasis, seborrheic dermatitis, and acanthosis nigricans. (Choice D) Dyskeratosis describes the abnormal, premature keratinization of individual keratinocytes. Dyskeratotic cells are strongly eosinophilic and may have a small, basophilic nuclear remnant. Dyskeratosis can be found in diseases such as squamous cell carcinoma. (Choice E) Spongiosis is intercellular epidermal edema that histologically appears as an increase in the width of spaces between cells. Spongiosis is often associated with spongiotic dermatitis, which encompasses a number of conditions (eg, eczematous dermatitis). Educational objective: Urticaria is a transient hypersensitivity disorder characterized by pruritic erythematous plaques that arise suddenly and resolve over hours. They are most often caused by IgE-mediated degranulation of mast cells, leading to increased permeability of the microvasculature with edema of the superficial dermis. __________ References: Pathogenic intracellular and autoimmune mechanisms in urticaria and angioedema. (http://www.ncbi.nlm.nih.gov/pubmed/22674016)

A 38-Year-Old Woman Comes to the Urgent Care Clinic with a 2-Day