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

IntroductionPeripheral 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). MethodsSSc 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. Results109 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 {micro}m IQR 3.0; p=0.01). Regarding thermoreceptor impairment, they presented with signifiantlly higer cold and warm thresholds (27.0 {degrees}C, IQR 3.0; vs 28.2 {degrees}C, p<0.001; 38.4 {degrees}C IQR 4.6, p=0.003 respectivelly), greater warm-cold threshold range (11.2 {degrees}C, IQR 6.9, p<0.001), and higher heat-induced pain threshold (44.8 {degrees}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. ConclusionFoot 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 .