An 80-year-old man visited our clinic with a two-day history of multiple painful, erythematous eruptions of the skin that had evolved into blisters with a linear distribution over his left flank. We diagnosed herpes zoster involving the left T11–12 dermatomes and prescribed oral famciclovir. The eruptions dried and healed in two weeks but were followed by a painless, reducible bulge, measuring 15 × 10 cm, in the left flank (Figure 1A). The bulge became more prominent when the patient stood or coughed. Abdominal sonography showed no evidence of an intra-abdominal mass. Electromyography was consistent with denervation limited to the left lumbar paraspinal muscles (T11–12 myotomes). We diagnosed a postherpetic pseudohernia. After 10 weeks, the bulge had completely resolved (Figure 1B).
Herpes zoster is caused by reactivation of varicella-zoster virus, which usually involves a solitary posterior root ganglion and sensory nerve fibres. Its symptoms include pain, itchiness, sensitivity of the skin and rash in affected dermatomes.1 Clinically significant motor deficit is rare, although subtle involvement of the paraspinal muscles has been described in up to 35% of instances of thoracic herpes zoster.2 The pathogenesis may be related to direct spread of virus to anterior horn cells, ventral roots or both. Motor deficits related to infection with varicella-zoster virus have also been described in the distributions of cranial nerves (e.g., Ramsay Hunt syndrome caused by herpes zoster affecting the geniculate ganglion), peripheral motor nerves (paralysis of limbs) and visceral nerves (dysfunction of the bladder). Most patients with pseudohernia after herpes zoster will recover in one year, without substantial sequelae.3
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Footnotes
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Competing interests: None declared.
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This article has been peer reviewed.