BACKGROUND: We present a rare case of sunburn-induced chronic neuropathic pain that was successfully treated with onabotulinumtoxinA (Ona A).

CASE REPORT: Due to a sunburn, a 21-year-old man developed painful dysesthesias and allodynia lasting more than 2 years on a 15 cm x 12 cm area of his chest. He was treated with 100 units of Ona A which was repeated at 12 weeks and then 200 units at 24 weeks. His pain reduced from 6/10 to 4/10 after the first 2 injections and to 3/10 after the third. He continued to improve to near resolution.

CONCLUSION: Ona A’s effect may be primarily peripheral, due to a decrease in the local release of nociceptive neurotransmitters. However, Ona A can be taken up by the neuron and pass multiple synapses; this may have led to a reduction in pain at the dorsal root ganglion, or more proximally. Lastly, a toxin-induced decrease of afferent mechanical and nociceptive input may have led to a central “wind-down” phenomenon.

KEYWORDS: Onabotulinumtoxin, botox, case report, central sensitization, peripheral sensitization, sunburn-induced neuropathic pain