Combined thermography and ultrasound in hidradenitis suppurativa: A preliminary study

Quantifying inflammatory activity in hidradenitis suppurativa (HS) remains challenging, since clinical assessment alone may underestimate subclinical inflammation. Ultrasound (US) is a validated imaging tool in HS,1 while medical infrared thermography (MIT) has been proposed as a complementary non-invasive biomarker of inflammation.2 However, data correlating imaging-based biomarkers with clinical severity indices remain limited, leaving their role in standardized assessment unclear. This preliminary observational study explored the relationship between thermographic findings, ultra-high frequency ultrasound (UHFUS) and disease severity in HS. An explorative cohort of patients affected by HS was evaluated in June 2025 at the Dermatology Unit of the University Hospital of Pisa. Clinical and demographic data were recorded, using the International Hidradenitis Suppurativa Severity Score System (IHS4) and Hurley score for disease severity. For imaging analysis, one or two clinically active target lesions per patient (inflammatory nodules, abscesses or draining tunnels) were selected. When multiple lesions were present, the most symptomatic was chosen. One atrophic scar served as control. Thermographic assessment was performed using a VarioCAM® HD Head 880 MED/30 mm camera (InfraTec, Dresden, Germany), a high-resolution long-wave MIT system designed for cutaneous temperature mapping. MIT acquisitions were performed on the selected lesion, the perilesional skin and, when clinically unaffected, the contralateral anatomical site. Measurement values were calculated as the mean of five repeated acquisitions per site. UHFUS was performed using a VEVO MD® system (FUJIFILM, Toronto, Ontario, Canada) equipped with a 70-MHz transducer, with a colour Doppler sensitivity threshold of 1.9 cm/s. Doppler signal intensity was classified on an ordinal scale (0 = absent, 1 = mild, 2 = moderate, 3 = severe). All examinations were performed by certified dermatologists and dermatology residents with specific training and experience in UHFUS, MIT and HS. Correlations between clinical and imaging parameters were assessed using Spearman's correlation (Jamovi software). Seven HS patients (3 male, 4 female; mean age 48.6 ± 17.5) were enrolled. Mean IHS4 score was 8.9 ± 11.3 with a mean disease duration of 9.8 ± 6.6 years. Three patients (42.8%) were active smokers. The most represented comorbidities were hypothyroidism and psoriasis (both 28.6%). A total of 10 lesions were analysed: three inflammatory nodules, three abscesses, three draining tunnels and one atrophic scar. Mean temperatures were 34.1 ± 1.4°C (lesional), 33.9 ± 1.2°C (perilesional) and 33.2 ± 1.1°C (contralateral non-affected skin). Lesional temperature showed a strong positive correlation with IHS4 (rho = 0.785; p = 0.012) and Hurley score (rho = 0.904; p < 0.001), as well as perilesional with both IHS4 (rho = 0.953; p < 0.001) and Hurley score (rho = 0.870; p = 0.002). Surprisingly, UHFUS showed no significant correlation with severity indices (Table 1). A representative example of multimodal evaluation is shown in Figure 1. Our preliminary analysis showed that lesional temperature demonstrated a strong and statistically significant correlation with IHS4 and Hurley score, confirming that focal hyperthermia reflects inflammatory burden in HS.3 Perilesional temperature also correlated with severity indices, supporting the hypothesis that the inflammatory process extends beyond the clinically visible lesions.2 Conversely, the lack of correlation between Doppler signal and severity suggests that vascular flow alone may inadequately reflect inflammatory activity, possibly due to technical limitations of conventional Doppler in detecting low-velocity microvascular flow.4 However, these findings should be carefully interpreted given the small sample size, exploratory design of the study, which precluded formal comparisons between different lesion subtypes and did not allow assessment of inter-observer variability. Overall, temperature-based diagnostics may better capture clinically meaningful inflammation in HS, while UHFUS remains essential for anatomical assessment and staging, particularly for identifying subclinical features, like microtunnels, that may significantly influence disease management.5 To conclude, our findings support the dual integration of UHFUS and MIT assessment into routine clinical evaluation and provide a rationale for future studies on larger cohorts with both patient-level and lesion-level analyses, validating comprehensive longitudinal monitoring strategies in HS. This article has no funding source. All authors have no relevant conflict of interest to declare. This study was conducted in accordance with the Declaration of Helsinki and was approved by the local Institutional Ethics Committee (IRB approval number: 20/16). The patients in this manuscript have given written informed consent to the publication of their case details. The data that support the findings of this study are available from the corresponding author upon reasonable request.