Diagnosis: Lichen planus pemphigoides of the penis
Lichen planus pemphigoides (LPP) is an uncommon skin disorder, generally considered a clinical, histopathological, and immunological coexistence of lichen planus (LP) and bullous pemphigoid (BP). However, growing evidence suggests that it should be considered as a separate disease entity (1–4).
Its prevalence is unclear, with male predominance and onset mainly in the 45th decade of life.
Aetiology is idiopathic in most cases; however, onset of LPP has been associated with ultraviolet (UV) exposure, hepatitis B virus, Castleman’s disease, chronic lymphocytic leukaemia, and several drugs, such as cinnarizine, angiotensin-converting enzyme (ACE) inhibitors, simvastatin, paracetamol, and ibuprofen (1–4).
LP usually precedes the onset of the bullous dermatosis; according to this, some authors have suggested an epitope spreading phenomenon, in which a primary inflammatory damage at the level of basal cell layer during LP causes antigenic exposure and a secondary autoimmune response against hemidesmosomal unit. IgG autoantibodies to either 1 or both the 230-kDa and 180-kDa BP (type XVII collagen) antigens have been demonstrated (5, 6). Clinical features of LPP classically include vesicles, tense bullae or erosions affecting both normal skin and skin previously affected by lichenoid dermatosis; this contrasts with bullous LP, which presents with bullae that are limited to longstanding LP lesions (1–4).
Diagnosis may be confirmed by the histopathological evidence of subepidermal bullae with a band-like leukocyte infiltrate, composed mainly of lymphocytes, plasma cells, and eosinophils in the dermis. DIF reveals a linear IgG and C3 deposit along the DEJ (1–4).
Most cases respond well to systemic corticosteroids, alone or in association with tetracyclines and nicotinamide (2–4). Other drugs include azathioprine, mycophenolate mofetil and dapsone, as used in the treatment of BP. Also, various patients with LPP presented a good response to cyclosporine or methotrexate, although they are usually poorly effective in the management of autoimmune bullous diseases (7–9). The prognosis of LPP is usually good, with a low rate of recurrence (approximately 20%). LPP of genital mucosae is uncommon and appears mostly when other sites are involved, on skin or oral mucosae. Mangin et al. (7) reported a case of LPP with erosion of the glans penis and diffuse cutaneous involvement, and Loyal et al. (8) described a case of vulvar and oral LPP. Therefore, isolated LPP could be a real challenge for clinicians, mostly in its early stage.
In particular, penile LPP should be distinguished from clinically similar conditions, such as bullous or erosive LP, mucous membrane pemphigoid, genital pemphigus, or penile fixed drug eruption (10).
Due to the patient’s poorly controlled diabetes and hypertension, systemic corticosteroids and cyclosporine were avoided, and methotrexate 15 mg/week was prescribed with significant improvement after 8 weeks.
To our knowledge, this is the first description of LPP clinically limited to the glans. This case suggests that this uncommon disease should be taken into consideration in the differential diagnosis of lichenoid or erosive balanoposthitis.
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