Prevalence and impact of foot peripheral neuropathy in Systemic Sclerosis (SSc): results from a single centre cross-sectional study.

Introduction: Peripheral Sensory Neuropathy (PSN) is an under-recognized feature in systemic sclerosis (SSc). Moreover, SSc foot involvement is frequent but poorly investigated. We aimed to provide a detailed characterization of foot peripheral neuropathy in a large cohort of SSc patients, describing its associations with disease-specific features, physical disability and Quality of Life (QoL). Methods: SSc patients and healthy controls (HC) comparable for age and gender, were enrolled in a cross-sectional observational case-control study. All subjects underwent a detailed quantitative sensory testing (QST) of feet evaluating touch, vibratory, thermal, and pain sensitivity; ultimately investigating the presence of large and small fiber neuropathy. Neuroptahtic symptoms were captured through a numerical rating scale assessing the presence of paraesthesia, numbness, burning, and stabbing pain. While the Manchester Foot Pain and Disability Index (MFPDI), SSc Health Assessment Questionnaire Disability Index (HAQ-DI), and the Systemic Sclerosis Quality of Life (SScQoL) needs-based questionnaire were used to capture the impact of the PSN on foot disability and QoL. Results: 109 SSc patients (88.1% female, median age 59.0 years) and 51 HC were enrolled. SSc patients presented with a significant median reduction of areas with preserved tactile sensitivity (14 IQR 4; p<0.001), and a delayed vibration perception threshold (1.7 μm IQR 3.0; p=0.01). Regarding thermoreceptor impairment, they presented with signifiantlly higer cold and warm thresholds (27.0 °C , IQR 3.0; vs 28.2 °C, p<0.001; 38.4 °C IQR 4.6, p=0.003 respectivelly), greater warm-cold threshold range (11.2 °C, IQR 6.9, p<0.001), and higher heat-induced pain threshold (44.8 °C, IQR 3.5; p<0.001),. At group level, 85.3% patients showed PSN on the feet, with 80% having small fibre involvement and 57% having large fiber neuropathy; while the coexistence of the two was present in 51.4% of the cases. Leaving only 14% without neuropathy. From those patients with PSN, 80.6% reported at least one neuropathic symptom, while 18% were asymptomatic. PSN was associated with age, smoking, foot ulceration,disease duration and corticosteroids use. Patients with neuropathic symptoms reported worse physical function, worse foot disability, and poorer QoL. Conclusion: Foot PSN presents as common and disabling manifestation in patients with SSc, involving both large and small fibers, often co-existing. Clinically, the presence of neuropathic symptoms might serve as an indicator of PSN, although it can have a subclinical presentation. Hence, PSN assessment should be included as part of the workup of the SSc patient .