CHAPTER 67 ■ RASH: VESICULOBULLOUS MARISSA J PERMAN INTRODUCTION Basic to all vesiculobullous (blistering) disorders is the disruption of cellular attachments Blister formation, therefore, follows intracellular degeneration, intercellular edema (spongiosis), or damage to the anchoring structures associated with the basement membrane (hemidesmosomes, basal lamina, anchoring fibrils) The location of these changes can help the physician ascertain a specific diagnosis When histologic information is not readily available or nondefinitive, however, the historical and clinical features of the case must be relied on This chapter will discuss the following entities: infestations, mastocytosis, inherited blistering disorders, acquired autoimmune bullous disorders, friction blisters, and frostbite, as well as the differential and workup for these blistering skin disorders ACQUIRED BLISTERING ERUPTIONS Infestations Insect Bites Insects generally bite exposed skin surfaces Therefore, heaviest involvement occurs on the head, face, and extremities Mosquito bites occur in the warm weather months, whereas flea (Pulex irritans ) bites and bed bug (Cimex lectularius ) bites occur throughout the year Historical information should address contact with pets, recent camping trips or involvement in outdoor activities, and known exposure in close contacts When blisters are present, the more characteristic urticarial papules are usually present in nearby locations, often clustered together or aligned linearly This linear arrangement is often referred to as “breakfast, lunch, and dinner.” The differential includes bullous impetigo, which can easily be ruled out with a Gram stain or bacterial culture In the case of bullous insect bites, the lesions should be negative for bacteria but can occasionally become secondarily infected If there is concern for flea bites, all pets should be evaluated by a professional Bed bugs can be very difficult to locate but may be detected by turning on the lights late at night and inspecting along the mattress seams and legs of the bed Symptomatic treatment for insect bites includes mild to moderate potency topical corticosteroids and antihistamines such as diphenhydramine Scabies While scabies in older children and adults most commonly presents as numerous ill-defined scaling, erythematous papules, interdigital scaling, and lesions in folds such as the umbilicus, groin, and axillae, infants and very young children can have vesiculobullous lesions on the palms ( Fig 67.1 ), soles, head, and face It is important not to be misled by this distribution and appearance Occasionally, the lesions can be nodular and often involve the genitals and axillae in young children Generally, the parents or other close family contact are also affected and exhibit the typical appearance and pruritus of this disorder First-line therapy for scabies includes permethrin cream (from the head down in infants age >2 months and older, neck down in older children and adults) applied twice, week apart, and washing all fomites in hot water followed by drying on high heat Fomites not amenable to washing may be dry-cleaned or placed in an airtight bag for several days All close contacts should be treated Ivermectin has also been used successfully Acropustulosis of Infancy The appearance of pruritic vesicopustules in infants and young children on the palms and soles ( Fig 67.2 ) may also suggest acropustulosis of infancy Vesicles often involve the lateral aspects of the fingers, palms, and soles This condition may be misdiagnosed as dyshidrotic eczema and is similarly pruritic Some speculate a relationship with antecedent scabies infestation in a subset of patients and may refer to this phenomenon as postscabetic pustulosis in this setting Cyclic eruptions occur every to weeks, lasting to 10 days Spontaneous disappearance occurs at to years of age Treatment with topical steroids may moderate some of the pruritus For a complete differential of acute vesiculobullous eruptions involving the palms and soles, see Table 67.1 MASTOCYTOSIS Cutaneous mast cell disease (mastocytosis or urticaria pigmentosa) may cause blistering in young children and may be associated with activating c-KIT mutations Red-brown lesions ( Fig 67.3A ) that blister after stroking or trauma (Darier sign) indicate the release of histamine from mast cells ( Fig 67.3B ) This collection may be isolated (mastocytoma) or generalized (urticaria pigmentosa or bullous mastocytosis) In addition to stroking, other triggers include mast cell destabilizers such as nonsteroidal anti-inflammatory drugs (NSAIDs), polymyxin B, some anesthetic medications (both topical and systemic), venom from bees or wasps, and narcotics Additionally, extreme temperatures or sudden changes in temperature may lead to mast cell destabilization and histamine release Refer to www.mastokids.org for more information about common mast cell degranulation triggers Blistering of such lesions generally occurs in the first few years of life After this time, urticaria occurs more often than blistering Lesions may be generalized and are often associated with more severe cutaneous disease or rarely systemic mastocytosis When a presumed melanocytic lesion feels infiltrated, the physician should think of mastocytosis—Darier sign will confirm the diagnosis If asymptomatic and localized, active nonintervention is appropriate For symptomatic disease, primary treatment is aimed at preventing histamine release with H1 and H2 antihistamines The majority of patients have regression over time FIGURE 67.1 Blisters on hands of a child with scabies FIGURE 67.2 Note vesicles and pustules on a child’s palm with acropustulosis of infancy