Dermatologic ultrasonography applications are rapidly growing in all skin fields. Thanks to very high spatial resolution, high-frequency and ultra-high-frequency ultrasound can evaluate smaller structures, allowing us to improve diagnosis accuracy and disease activity. Moreover, they can guide treatment, such as drug injection, and assess therapy efficacy and complications. In this narrative review, we evaluated high-frequency ultrasound and ultra-high-frequency ultrasound in infections, inflammatory dermatoses, metabolic and genetic disorders, specific cutaneous structure skin disorders, vascular and external-agent-associated disorders, neoplastic diseases, and aesthetics.

Psoriatic onychopathy is one of the clinical presentations of psoriasis and a well-known risk factor for the development of psoriatic arthritis. High-frequency ultrasounds (HFUS > 20 MHz) have recently been used to evaluate the nail apparatus of healthy and psoriatic subjects. The aim of our study was to detect by means of ultra-high-frequency ultrasound (UHFUS 70–100 MHz) alterations of the nail bed and matrix in patients with psoriatic onychopathy and to monitor these parameters during the treatment with monoclonal antibody (mAb). We enrolled 10 patients with psoriatic onychopathy and naive to previous biologic therapies. Patients were evaluated at baseline, after 1 month and after 3 months from the beginning of mAb therapy by a complete clinical assessment and US evaluation. A UHFUS examination with a 70 MHz probe was performed on the thumbnail (I), the index fingernail (II) and the nail with greater clinical impairment (W). The following measurements were analyzed: nail plate thickness (A), nail bed thickness (B), nail insertion length (C), nail matrix length (D) and nail matrix thickness (E). Among the various parameters analyzed, some measures showed a statistically significant decrease with p-value < 0.05 (t0 WA = 0.52 mm vs. t2 WA = 0.42 mm; t0 WB = 2.8 mm vs. t2 WB = 2.4 mm; t0 WE = 0.76 mm vs. t2 WE = 0.64 mm; t0 IIA = 0.49 mm vs. t2 IIA = 0.39 mm). In conclusion, UHFUS could represent a viable imaging technique for the real-time evaluation and monitoring of psoriatic onychopathy, thus supporting the clinical parameters and revealing any subclinical signs of early drug response.

Atopic dermatitis (AD) is a chronic multifactorial inflammatory disease characterized by intense itching and inflammatory eczematous lesions. Biological disease-modifying drugs, such as dupilumab are recommended for patients with moderate-to-severe AD, refractory to systemic immunosuppressive therapies. Disease monitoring is performed by clinical scores. Since 1970, however, the use of ultrasound and particularly high-frequency ultrasound (HFUS), has identified alterations in dermal echogenicity, called the subepidermal low-echogenic band (SLEB), that correlates with disease severity and response to treatment. We enrolled 18 patients with moderate-to-severe AD, divided into two groups: twelve patients in the dupilumab treatment (Group A) and six patients in standard treatment, from February 2019 to November 2019. We performed ultra-high frequency ultrasound (UHFUS) evaluation of lesional and non-lesional skin, focusing on SLEB average thicknesses measurement, epidermal thickness, and vascular signal in correlation with objective disease scores (EASI, IGA), patient’s reported scores (Sleep Quality NRS and Itch NRS), and TEWL and corneometry at baseline (T0), after 1 month (T1) and 2 months (T2). The SLEB average thickness measurement, vascular signal, and epidermal thickness showed a statistically significant reduction in lesional skin of the biological treatment group and no significant reduction in non-lesional skin in both groups. In the lesional skin of the standard treatment group, only epidermal thickness showed a statistically significant reduction. Our study demonstrates that SLEB measurement, vascular signals, and epidermal thickness could be used as objective parameters in monitoring the AD treatment response, while the presence of SLEB in non-lesional skin could be used as a marker of subclinical inflammation and could predict development of clinical lesions, suggesting a pro-active therapy. Further follow-up and research are needed to clarify the association of SLEB decrease/disappearance with a reduction of flares/prolongment of the disease remission time.

Dermal hyaluronic acid (HA) fillers are used for nasolabial fold correction, but no study is still available on the use of ultra-high-frequency ultrasound (UHFUS) with 70 MHz probes for the evaluation of HA distribution and wrinkle amelioration. We selected 13 patients who received HA filler, evaluated before (Time (T) 0) and after injection (T1), and after 24 weeks (T2). The dermal thickness and distribution of HA were registered, as well as the Wrinkle Severity Rating Scale (WSRS), Global Aesthetic Improvement Scale (GAIS), and wrinkle 3D fullness. The UHFUS dermal thickness was increased by 11% for both sides at T1 and by 7.4% and 6.8% for the right and left side, respectively, at T2 (p < 0.01). The 3D wrinkle fullness showed a T1 increase (+0.59 cc and +0.79 cc for the right and left side, respectively) with a T2 maintenance of 45% of the T1 fullness (p-value < 0.001). The only clinical score significantly modified was WSRS, with a reduction of 56% at T1 and of 47.1% at T2 (p-value < 0.001). Our study then demonstrated the efficacy of UHFUS in the assessment of nasolabial fold correction, representing also the first multi-modal evaluation of HA persistence and its visual subsequent aesthetic results.

Pyoderma gangrenosum (PG) is a neutrophilic dermatological disease, whose pathogenesis is still poorly clarified. Because of the lack of validated criteria for diagnosis and response, PG treatment is still challenging and should be differentiated in the inflammatory and non-inflammatory phases. Our study aimed to provide a new semi-quantitative approach for PG diagnosis and monitoring, identifying ultra-high-frequency ultrasound (UHFUS) early biomarkers associated with the transition between the two phases. We enrolled 13 patients affected by painful PG lesions evaluated during the inflammatory phase (T0) and during the non-inflammatory phase (T1): pain was measured by the Visual Analogue Scale (VAS); clinical features were recorded through digital photography; epidermis and dermis ultrasound (US) characteristics were evaluated by UHFUS examination with a 70 MHz probe (Vevo MD^® FUJIFILM VisualSonics). In T1 UHFUS examination, the presence of hyperechoic oval structures was lower compared to T0 (p value < 0.05). An hyperechogenic structure within the oval structure, suggestive of a hair tract, was evident in T0 and absent in T1 (p value < 0.05). In T0, blood vessels appear as U-shaped and V-shaped anechoic structures with a predominance of U-shaped vessels (p value < 0.05) compared to the more regular distribution found in T1. Finding early biomarkers of the transition from the inflammatory to the non-inflammatory phase could provide new insight in terms of therapeutic decision making and response monitoring. The differences found by this study suggest a potential use of UHFUS for the development of an objective standardized staging method. Further investigations will be necessary to confirm our preliminary results, thus providing a turning point in PG early detection, differential diagnosis and treatment monitoring.