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Sequential Development of Herpes Zoster Duplex Unilateralis during Oral Famciclovir Treatment

To the Editor: Herpes zoster duplex is a rare subtype of herpes zoster which involves two noncontiguous dermatomes simultaneously or sequentially. The subtypes have been referred to as duplex unilateralis or bilateralis, depending whether one half or both halves of the body are involved (1). We report a case of herpes zoster duplex unilateralis that developed sequentially despite famciclovir treatment. A 50-year-old Korean woman presented with painful grouped vesicles on the left chest wall corresponding to the T2 dermatome. She had a history of infiltrating ductal cell carcinoma of the left breast and had undergone unilateral modified radical mastectomy nine years previously. Thereafter, she had had no adjuvant therapies and there was no sign of recurrence on regular follow-ups. With the diagnosis of herpes zoster, treatment was commenced with oral famciclovir 750 mg daily for seven days. After these seven days, the initial skin lesions had mostly improved and crusted, but newly developed grouped vesicles were noted on the left side of her abdomen corresponding to the T8 dermatome. (Fig. 1). An additional course of famciclovir was followed, and the second set of skin lesions were cleared up by 14 days thereafter. Although the pathogenesis of multiple dermatomal involvement is not clear, there are at least three possible explanations in our case. First, insufficient drug dosage may have been the cause of failure in preventing the sequential appearance. The national health insurance of some countries, including ours, limits the dosage of famciclovir for herpes zoster patients. Although nucleoside analogues only control symptoms of the disease or prevent outbreaks and cannot cure the infection (2), the restricted dosage could result in an insufficient effect on the disease. Secondly, as shown in a previous report (1), an association between a systemic condition, such as immunocompromised host status, and dissemination or multiplicity of the skin lesions can be presumed. Although no tests for immune function were performed, our patient neither received any immunosuppressive treatments nor showed any clinical features suggesting decreased immunity. Thirdly, resistance to the antiviral agents can be involved. Resistance is an emerging issue in conventional antiviral The Journal of Dermatology Vol. 32: 933–934, 2005