Case report

A 70-year-old man with a history of right knee osteoarthritis presented with a painful eruption on the right lower extremity that began 5 days after intra-articular triamcinolone acetonide injection consisting of 2 mL of a 40 mg/mL solution (total dose 80 mg). He had no history of immunosuppression, malignancy, or chronic systemic corticosteroid use.

The eruption initially consisted of grouped vesicles that progressed over several days to hemorrhagic, crusted erosions in a dermatomal distribution along the anterior aspect of the right lower leg. The patient reported localized pain but denied fever, chills, or systemic symptoms. On physical examination, grouped hemorrhagic crusted erosions and vesicles were present on the anterior right lower leg in a dermatomal pattern (Fig 1).

Fig 1: Grouped hemorrhagic crusted erosions on the anterior surface of the right lower extremity.

A punch biopsy of a representative lesion was performed. Histopathologic examination demonstrated ulceration with epidermal necrosis and an associated superficial and deep dermal perivascular lymphocytic inflammatory infiltrate (Fig 2, A). Higher magnification revealed degenerated epithelial cells with viropathic changes, including multinucleation and chromatin margination (Fig 2, B). Immunohistochemical staining for VZV was strongly positive in lesional epithelial cells (Fig 2, C), supporting the diagnosis of herpes zoster. The diagnosis of leukocytoclastic vasculitis (LCV) was supported by the presence of fibrinoid vascular necrosis with leukocytoclasia and hemorrhage (Fig 3).

Fig 2: A, Low-power view (2×) demonstrating superficial and mid-dermal perivascular inflammatory infiltrates (yellow arrows). Hematoxylin and eosin stain. B, High-power view (30×) showing viral cytopathic changes, including multinucleation (light blue arrow) and chromatin margination (magenta arrow). Hematoxylin and eosin stain. C, Varicella-zoster virus immunostain highlighting viral antigen within lesional keratinocytes. 3,39-diaminobenzidine chromogen with hematoxylin counterstain.

Fig 3: High-power view (30×) showing fibrinoid vascular necrosis with leukocytoclasia and hemorrhage. Hematoxylin and eosin stain (yellow arrows).

Based on clinical, histopathologic, and immunohistochemical findings, a diagnosis of herpes zoster with associated cutaneous LCV was established. The patient was treated with a 7-day course of valacyclovir and triamcinolone 0.1% topical cream, and the eruption resolved completely within 2 weeks, without recurrence or postherpetic neuralgia at 3 months of follow-up.