Intralesional botulinum toxin proven safe, effective in nail psoriasis

A single injection of intralesional botulinum toxin (BTX) demonstrates long-term efficacy and is well tolerated in patients with nail psoriasis, according to a randomized intraindividual controlled study presented at the recent WCD 2023. BTX is also as effective as multiple intralesional steroid injections.

“The treatment of nail psoriasis is considered challenging and difficult to treat,” said the researchers, led by Premjit Juntongjin from the Chulabhorn International College of Medicine, Thammasa University, Pathum Thani, Thailand.

“According to novel insights of cutaneous neurogenic inflammation in the pathogenesis of psoriasis, BTX has been proposed to play a potential role of neuromodulator for treatment,” they added.

Juntongjin and her colleagues examined the use of BTX injection in patients with at least four psoriatic fingernails in this study. Each nail had the target Nail Area Psoriasis Severity Index (NAPSI) score of at least 3 points.

Selected nails were randomly assigned to receive one of the four treatment regimens: (1) a single intralesional BTX injection at baseline, (2) intralesional triamcinolone acetonide (TA) injection twice at baseline at 8 weeks, (3) topical vitamin D or steroid application once daily for 16 weeks, and (4) no treatment, which served as the control group.

Juntongjin and her team evaluated the target NAPSI score of each affected nail and the adverse reactions every 8 weeks up until week 24.

Overall, 64 affected fingernails were included in the study. Statistically significant improvements were noted in both injections and topical medications. [Juntongjin P, et al, World Congress of Dermatology 2023]

At weeks 16 and 24, patients receiving the intralesional BTX injection achieved 36.3 percent and 41.1 percent of the target NAPSI score reduction, respectively, while those on TA attained 48 percent and 45.6 percent of the target score, respectively. No significant difference in overall improvement was observed between both injections.

“With all three treatment options, significant improvements [were observed] compared to baseline,” Juntongjin said. “However, there was no significant difference between [the] injection groups at any point of time.”

Nail bed improvement

On week 24, intralesional BTX injection resulted in a 61.3-percent nail bed improvement compared with 42.3 percent for TA (p=0.038). No significant difference in pain and adverse reactions was seen among all regimens involved.

“For our study … the single injection of BTX is comparable to multiple injections of intralesional corticosteroid, with long-lasting efficacy, especially in nail bed involvement,” Juntongjin said. “And we cannot see [a] significant difference in adverse reactions and pain.”

These findings were consistent with those of an earlier study that used a mouse model, in which significant improvements were observed as early as 2 weeks after a single intradermal injection of BTX. Moreover, the study showed that BTX reduced acanthosis, dendritic cells, and the number of T cells. [J Invest Dermatol 2012;132:1927]

“Nail psoriasis is refractory and difficult to treat,” said Juntongjin. “[The] number of nail involvement, the patients’ needs, and the impact of the disease on the quality of life should be considered to determine treatment. BTX could be a potential treatment for nail psoriasis via neuromodulatory effects.”