Microscopic examination of the biopsy specimen showed hyperkeratosis, mild parakeratosis, acanthosis, and elongation of rete ridges. A subcorneal pustule consisting of granulocytes, mononuclear cells, and fibrin was seen. The upper dermis contained mild edema and a mild perivascular mononuclear infiltrate.
Based on the clinical and histologic findings in this case, the diagnosis was ACH. Treatment with multiple topical regimens, including potent topical corticosteroids, calcipotriene ointment, tretinoin cream, and 5% fluorouracil cream, was initiated, with no significant improvement. Systemic treatments with colchicine (1.5 mg/d) and acitretin (0.75 mg/kg for 3 months) were unsuccessful as well.
Chronic Pustular Eruption of the Thumbs. Arch Dermatol. 2000;136(7):925-930. doi: