Wolf's isotopic response: Trichophyton rubrum folliculitis appearing on a herpes zoster scar

A 37‐year‐old man was first seen in November 1998 with a unilateral painful eruption of grouped small vesicles at the right side of his thorax. His general health was good. He was diagnosed as having herpes zoster, which was successfully, treated with oral acyclovir 800 mg, five times a day. Five months later, and after complete resolution of the herpes zoster, he developed a pustular eruption on exactly the same area of his first herpetic lesion. There was a diffuse distribution of pustules on the dorsal part of the dermatome, and a grouped pattern on the ventral side ( Fig. 1). A punch biopsy was performed for differential diagnosis of recurrent herpes zoster and folliculitis. Methicillin‐resistant Staphylococcus aureus colonies were isolated from the bacterial culture of the pustular content. Cefadroxil monohydrate 500 mg twice a day and the application of fucidic acid ointment were prescribed. There was no improvement at the end of the second week of therapy. 1 Clinical appearance A histopathologic study demonstrated hyperkeratosis, acanthosis, focal accumulation of neutrophils and bacteria in the epidermis, and a perivascular and perifollicular infiltration of eosinophils, lymphocytes, and histiocytes in the dermis ( Fig. 2). After the diagnosis of eosinophilic pustular dermatosis was histopathologically confirmed, fungal folliculitis and immunosuppressive conditions were investigated. Routine blood tests were within the normal ranges. The human immunodeficiency virus (HIV), hepatitis C virus (HCV), and anti‐hepatitis B surface antibody (anti‐HBs) tests were negative, but the hepatitis B surface antigen (HBsAg) test was positive. Abundant fungal hyphae were seen in potassium hydroxide under direct microscopic examination of the pustule content, and a fungal culture was performed. Although no evidence of fungal infection was demonstrated in repeated periodic acid–Schiff (PAS) staining of punch biopsy specimens, Trichophyton rubrum was isolated from fungal culture. The patient was then given a regimen of itraconazole pulse therapy (400 mg/day, for 7 days a month, repeating the monthly cycle three times) and cycloproxolamine cream. Two months later, at the end of therapy, only a few pustules remained, and these completely disappeared after another 5 months. 2 Eosinophilic pustular folliculitis: dense eosinophilic infiltration within and around the hair follicle (hematoxylin and eosin, × 400)