Chapter 055. Immunologically Mediated Skin Diseases (Part 5)

Pemphigoid Gestationis Pemphigoid gestationis (PG), also known as herpes gestationis, is a rare, nonviral, subepidermal blistering disease of pregnancy and the puerperium. PG may begin during any trimester of pregnancy or present shortly after delivery. Lesions are usually distributed over the abdomen, trunk, and extremities; mucous membrane lesions are rare. Skin lesions in these patients may be quite polymorphic and consist of erythematous urticarial papules and plaques, vesiculopapules, and/or frank bullae. Lesions are almost always very pruritic. Severe exacerbations of PG frequently occur after delivery, typically within 24–48 h. PG tends to recur in subsequent pregnancies, often beginning earlier...
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Chapter 055. Immunologically Mediated Skin Diseases (Part 5) Chapter 055. Immunologically Mediated Skin Diseases (Part 5) Pemphigoid Gestationis Pemphigoid gestationis (PG), also known as herpes gestationis, is a rare,nonviral, subepidermal blistering disease of pregnancy and the puerperium. PGmay begin during any trimester of pregnancy or present shortly after delivery.Lesions are usually distributed over the abdomen, trunk, and extremities; mucousmembrane lesions are rare. Skin lesions in these patients may be quitepolymorphic and consist of erythematous urticarial papules and plaques,vesiculopapules, and/or frank bullae. Lesions are almost always very pruritic.Severe exacerbations of PG frequently occur after delivery, typically within 24–48h. PG tends to recur in subsequent pregnancies, often beginning earlier duringsuch gestations. Brief flare-ups of disease may occur with resumption of mensesand may develop in patients later exposed to oral contraceptives. Occasionally,infants of affected mothers demonstrate transient skin lesions. Biopsies of early lesional skin show teardrop-shaped subepidermal vesiclesforming in dermal papillae in association with an eosinophil-rich leukocyticinfiltrate. Differentiation of PG from other subepidermal bullous diseases by lightmicroscopy is difficult. However, direct immunofluorescence microscopy ofperilesional skin from PG patients reveals the immunopathologic hallmark of thisdisorder—linear deposits of C3 in epidermal basement membrane. These depositsdevelop as a consequence of complement activation produced by low titer IgGanti-basement membrane autoantibodies directed against BPAG2, the samehemidesmosome-associated protein that is targeted by autoantibodies in patientswith BP—a subepidermal bullous disease that resembles PG clinically,histologically, and immunopathologically. The goals of therapy in patients with PG are to prevent the development ofnew lesions, relieve intense pruritus, and care for erosions at sites of blisterformation. Many patients require treatment with moderate doses of dailyglucocorticoids (i.e., 20–40 mg prednisone) at some point in their course. Mildcases (or brief flare-ups) may be controlled by vigorous use of potent topicalglucocorticoids. Infants born of mothers with PG appear to be at increased risk ofbeing slightly premature or small for dates. Current evidence suggests that thereis no difference in the incidence of uncomplicated live births in PG patients treatedwith systemic glucocorticoids and in those managed more conservatively. Ifsystemic glucocorticoids are administered, newborns are at risk for developmentof reversible adrenal insufficiency. Dermatitis Herpetiformis Dermatitis herpetiformis (DH) is an intensely pruritic, papulovesicular skindisease characterized by lesions symmetrically distributed over extensor surfaces(i.e., elbows, knees, buttocks, back, scalp, and posterior neck) (see Fig. 52-8).Primary lesions in this disorder consist of papules, papulovesicles, or urticarialplaques. Because pruritus is prominent, patients may present with excoriations andcrusted papules but no observable primary lesions. Patients sometimes report thattheir pruritus has a distinctive burning or stinging component; the onset of suchlocal symptoms reliably heralds the development of distinct clinical lesions 12–24h later. Almost all DH patients have an associated, usually subclinical, gluten-sensitive enteropathy (Chap. 288), and >90% express the HLA-B8/DRw3 andHLA-DQw2 haplotypes. DH may present at any age, including childhood; onset inthe second to fourth decades is most common. The disease is typically chronic. Biopsy of early lesional skin reveals neutrophil-rich infiltrates withindermal papillae. Neutrophils, fibrin, edema, and microvesicle formation at thesesites are characteristic of early disease. Older lesions may demonstrate nonspecificfeatures of a subepidermal bulla or an excoriated papule. Because the clinical andhistologic features of this disease can be variable and resemble other subepidermalblistering disorders, the diagnosis is confirmed by direct immunofluorescencemicroscopy of normal-appearing perilesional skin. Such studies demonstrategranular deposits of IgA (with or without complement components) in thepapillary dermis and along the epidermal basement membrane zone. IgA depositsin the skin are unaffected by control of disease with medication; however, theseimmunoreactants may diminish in intensity or disappear in patients maintained forlong periods on a strict gluten-free diet (see below). Patients with DH havegranular deposits of IgA in their epidermal basement membrane zone and shouldbe distinguished from individuals with linear IgA deposits at this ...