A case of anti-laminin 332-type mucous membrane pemphigoid mimicking linear IgA bullous dermatosis

A 68-year-old man presented with erythematous lesions and tense bullae on the trunk and extremities, accompanied by oral mucosal erosions, after he suffered from a flu-like illness marked by high fever and sore throat.The patient denied any recent medication use, including antibiotics or nonsteroidal anti-inflammatory drugs.Upon referral to our hospital, physical examination revealed erosion of the oral and nasal mucosa, with hemorrhagic crusting on the lips and eyelids, and conjunctival involvement was absent.Annular erythematous plaques and bullae were widely distributed on the trunk, extremities, axillae, groins, palms, and soles (Fig 1, A). Histopathologic examination demonstrated subepidermal bullae (Fig 1, B), a mixed inflammatory infiltrate composed of lymphocytes and neutrophils, with scattered eosinophils.Question 1: Based on the clinical presentation and histopathologic findings, what is the most likely diagnosis?A. Erythema multiforme B. Bullous pemphigoid C. Pemphigus vulgaris D. Mucous membrane pemphigoid E. Linear IgA bullous dermatosis Answer:The correct answer is D, mucous membrane pemphigoid.Serum enzyme-linked immunosorbent assay results for anti-BP180 and anti-BP230 IgG were negative.Direct immunofluorescence revealed linear IgG deposition along the basement membrane zone, whereas IgA deposition was absent.Indirect immunofluorescence and salt-split indirect immunofluorescence results were negative.Immunoblotting using purified laminin-332 identified IgG reactivity against the a3 subunit (Fig 1, C ).Based on these findings, a diagnosis of anti-laminin 332-type mucous membrane pemphigoid (MMP) was established. DISCUSSIONMMP is a rare autoimmune subepidermal blistering disorder that predominantly involves mucosal surfaces, whereas cutaneous lesions are usually limited and less extensive.1 Classic MMP is characterized by chronic