Psoriasis, Psoriatic Arthritis Linked to Increased Polyneuropathy Risk

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Psoriasis and psoriatic arthritis may be linked to an increased polyneuropathy risk, according to recent findings, though factors contributing to polyneuropathy rather than a direct increase in risk were specifically associated with psoriatic disease.¹

These findings were the conclusion of new research led by Pietro E. Doneddu, MD, of the Neuromuscular and Neuroimmunology Unit at the IRCCS Humanitas Research Hospital in Milan, Italy. Doneddu and colleagues noted that there was a possible link between neurologically-mediated inflammation and psoriasis, though risk of neuropathy had continued to be unclear.²

Therefore, the study’s investigators sought to assess patients’ risk levels and provide descriptions of the features of peripheral neuropathy among those with psoriasis and psoriatic arthritis.

“Understanding the prevalence and clinical characteristics of peripheral neuropathy in patients with psoriasis or psoriatic arthritis would expand our knowledge of the pathogenetic mechanisms underlying these diseases, potentially enabling the implementation of targeted diagnostic and therapeutic approaches and improving the accuracy of prognosis,” Doneddu and colleagues wrote.¹

Background and Methods

The investigators enrolled study participants from January 2020 - December 2022, looking specifically at those with psoriasis and/or psoriatic arthritis diagnosis from the rheumatology and dermatology outpatient clinics of Humanitas Research Hospital in Milan, Italy.

Individuals who were shown to have these conditions were monitored every 3 to 6 months, though this depended on their clinical needs as well as their level of disease activity. Confirmation of psoriasis occurred through dermatologists, but psoriatic arthritis diagnosis was determined using a specific classification criteria.

The research team included patients with psoriasis and psoriatic arthritis who can sometimes undergo treatments such as anti-tumor necrosis factor (TNF) α agents, with the goal being to comprehensively assess their risk of developing peripheral neuropathy. Such patients can develop comorbidities such as diabetes and cancer, which can increase their risk of peripheral neuropathy.

Those determined to be control subjects were subjects without psoriasis or psoriatic arthritis who had also attended the dermatological clinic for the purposes of mole mapping. They were also enrolled in the study consecutively.

Those in the control arm had not been shown to have either melanoma or other neoplastic skin lesions. Patients and controls were given extensive assessments, with detailed medical histories and neurological assessments being done through the help of neurologists specializing in peripheral neuropathies.

Information was also supplemented through the use of medical records. The investigators determined that a clinical diagnosis of peripheral neuropathy would be made using an evaluation of the presence of symptoms and signs. Confirmation of diagnoses involved the utilization of skin biopsies, electrophysiological exams, and nerve ultrasounds for confirmed polyneuropathy occurrences.

Findings

Overall, it was found that 9 individuals were given a polyneuropathy diagnosis. This was not present in any of the control arm subjects, demonstrating a relative risk (RR) of 19.00 to the investigators, with a 95% confidence interval (CI) of 1.12 - 322.11.

Individuals with psoriasis had an RR of 22.09 (95% CI of 1.17 - 416.43) when the research team evaluated the specific relative risks, and subjects known to have psoriatic arthritis were found to have an RR of 18.75 (95% CI of 1.07 - 327.62). The team reported that the polyneuropathy seen in all 9 subjects had led to minimal or no disability and been characterized as symmetrical, length-dependent, and predominantly sensory.

The investigators also found that comorbidities and exposure to treatments known to raise patients’ risk of polyneuropathy had been shown to be more common among those who had diagnoses of psoriasis and/or psoriatic arthritis versus those in the control arm (42% versus 4%, P = .0001).

Following their exclusion of potential contributory factors, the research team’s analysis of the data showed that participants’ risk of polyneuropathy among those with psoriasis and/or psoriatic arthritis had not been statistically significant.

“If confirmed by additional studies, polyneuropathy should be included among the potential comorbidities associated with psoriasis and psoriatic arthritis,” they wrote. “Our study also suggests that psoriasis and psoriatic arthritis are not associated with an elevated risk of nerve entrapments.”

References

1. ^{Doneddu PE, Borroni R, Ceribelli A, et al. Risk of peripheral neuropathy in patients with psoriasis and psoriatic arthritis. A prospective cohort study. Muscle & Nerve. 2024; 1-8. doi:10.1002/mus.28196.}
2. ^{Naukkarinen A, Nickoloff BJ, Farber EM. Quantification of cutaneous sensory nerves and their substance P content in psoriasis. J Invest Dermatol. 1989; 92(1): 126-129.}