Eczema herpeticum and eczema vaccinatum in children

Histopathology of Cutaneous Inflammatory Disorders in Children

Inflammatory dermatoses encompass a variety of histologic patterns that affect different portions of the skin. In spongiotic, psoriasiform, lichenoid, pityriasiform, and blistering disorders, there are predominately epidermal and junctional activities with variable superficial dermal inflammation. Hypersensitivity reactions can show either epidermal or mostly dermal changes depending on whether the exposure of the exogenous allergen occurs through an external or internal route, respectively. Exceptions include erythema multiforme and Stevens-Johnson syndrome/toxic epidermal necrolysis, where the etiology is often due to infection or ingested medications, but the histologic features are almost exclusively confined to the epidermis and dermoepidermal junction. Autoimmune disorders are unique in that lesions typically incorporate a mixture of epidermal and dermal inflammatory patterns with periadnexal inflammation, while the vast majority of vasculitis/vasculopathy and alopecia have changes limited to only the vessels and hair follicles, respectively. It is critical to recognize that a relatively limited number of histologic patterns are seen in a large array of clinical entities. Therefore, clinicopathologic correlation and careful examination of histologic details are of the utmost importance when evaluating skin biopsies for inflammatory disorders.

Eczema

Atopic dermatitis, commonly known as eczema, is a common chronic, relapsing skin disease characterized by pruritus, disrupted epidermal barrier function, and immunoglobulin E-mediated sensitization to food and environmental allergens. Atopic dermatitis is a complex disease that arises from interactions between genes and the environment. Loci on several chromosomes have been identified, including a family of epithelium-related genes called the epidermal differentiation complex on chromosome 1q21. Mutations in filaggrin, a key protein in epidermal differentiation, have also been identified in early-onset and severe atopic dermatitis. There are 3 classical stages of eczema: infantile, childhood, and adulthood. The spectrum of eczema presentation varies widely from a variant that only affect the hand to major forms where a patient presents with erythroderma. The acute and subacute lesions of atopic dermatitis are often characterized by intensely pruritic, erythematous papules and vesicles with excoriations and a serous exudate. Chronic atopic dermatitis is exemplified by lichenified plaques and papules with excoriations. Atopic dermatitis patients are also at higher risk for skin infections, including bacterial and viral superinfections. Conventional therapy includes avoidance of irritants and potential allergens, as well as continued hydration of the skin with thick emollients. Topical corticosteroids and topical immunomodulators are often used primarily. Other therapies including phototherapy, antimicrobials, antihistamines, and systemic immunosuppressives are also options in certain situations.