๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
Contact pemphigus
Contact pemphigus
Differential diagnosis The differential diagnosis includes subcorneal pustular dermatosis, typical p. foliaceus, and infections such as bullous impetigo. Although clinically subcorneal pustular dermatosis tends to be more restricted to the flexural sites, absolute distinction from the subcorneal variant of IgA pemphigus depends
Clinical features There is a growing body of literature documenting contact with topical substances preceding the onset of pemphigus. The pathogenesis is not understood, but in some cases the exposure is thought somehow to trigger or induce pemphigus. The term โcontact pemphigusโ has been proposed as a designation for this phenomenon, which has been described in the vulgaris, vegetans, foliaceus, and erythematosus variants.1,2 Substances that have been implicated include nickel, pesticides, chromium sulfate, tincture of benzoin, phenol, diclofenac, dihydrodiphenyltrichlorethane, ketoprofen, feprazone, and imiquimod.1โ15 Clearly, further study is necessary to elucidate the relationship between exposure to topical agents and contact pemphigus.
Pathogenesis and histologic features Whether this phenomenon relates to systemic absorption, contact allergy, or a direct โtoxicโ effect on epidermal antigens is as yet unknown. It is
188 Acantholytic disorders
interesting to note that in the majority of documented cases, the patient has been exposed to the offending agent for a considerable length of time before the onset of the blistering eruption.6,15
Biopsy of contact pemphigus shows histologic features similar to those of p. vulgaris, although one patient developed features more reminiscent of p. vegetans. Immunofluorescent studies show intercellular IgG and sometimes C3.
Differential diagnosis The main differential diagnosis is with classic pemphigus. Only clinical information will allow distinction of contact pemphigus from other members of the pemphigus family of disorders.
An exceptional case of a patient developing the disease while on efalizumab for psoriasis has been reported.26 Symptoms often improve or even disappear during winter, but tend to worsen in summer.1,27 Mucosal involvement is unusual. Anogenital disease, however, occasionally presents as multiple 3โ5-mm-diameter warty papules.28 This occurs most often in females, particularly blacks, and sometimes may be a presenting feature. In such instances, there is overlap with papular acantholytic dyskeratosis of the genitocrural area.29โ31
Asymptomatic white longitudinal bands may be present on the fingernails in up to 70% of affected patients.1,32โ34 The other nail changes of Darier disease are absent.