Psoriasis Alba (White Psoriasis) of the Perianal Region

A 40-year-old man presented with pruritic perianal lesions existing for 18 months, accompanied by frequent burning sensation on defecating. He had received oral fluconazole 150 mg weekly for a presumptive diagnosis of candidosis earlier. There was no history of other mucocutaneous lesions or comorbidities. The patient denied any unprotected sexual exposure or having anal intercourse. Examination revealed a well-defined perianal, horseshoe-shaped, white-colored macerated plaque with fissures on the gluteal cleft (Figure 1) with tenderness. Examination of scalp, nail, and oral mucosa was unremarkable. Routine investigations, including complete blood counts and chemical profile, were within normal limits. His fasting glucose level was 85 mg/ dL and glycated hemoglobin (HbA1c) was 5.3. The Venereal Disease Research Laboratory (VDRL) test and testing for human immunodeficiency virus (HIV)-1 and 2 were nonreactive. A 10% potassium hydroxide (KOH) examination was negative for fungal elements. Differential diagnoses of flexural psoriasis, Hailey-Hailey disease, and lichen sclerosus were considered, and a skin biopsy for pathology and direct immunofluorescence was performed. The pathologic features showed epidermal acanthosis, hyperkeratosis with elongated rete ridges, and focal hypogranulosis. The upper part of the dermis showed a moderate perivascular mononuclear inflammatory infiltrate with a few melanophages (Figure 2). Direct immunofluorescence was negative. Based on pathologic features, a diagnosis of psoriasis alba was confirmed, and the patient was started on desonide lotion (0.05%) to be applied in the morning and tacrolimus cream (0.1%) at night, plus oral antihistamines. At the follow-up visit 3 weeks later, the lesions diminished to a great extent (Figure 3).