Mexametry as a way to dynamically monitor therapy in vitiligo patients

Dear Sir,

Vitiligo is a multifactorial depigmenting skin disorder which results in achromic macules and patches. First-line treatment includes narrow-band ultraviolet B (NB-UVB) phototherapy, alone or in combination with corticosteroids, calcineurin inhibitors, and immunosuppressants.^[1] Micro-needling is a new, minimally invasive procedure that promotes keratinocyte and melanocyte migration and enhances drug delivery.^[2,3] According to the literature, microneedling combined with 5-fluorouracil may cause repigmentation by overstimulation follicular melanocytes, increasing the number of melanosomes around the hair follicles.^[2] Although therapeutic response is highly variable, and repigmentation may not persist.^[4] Considering the variability of clinical outcomes, there is a growing requirement for objective tools for monitoring therapeutic response in vitiligo. This study evaluates the expediency of using mexametry.

In the period from October 2023 to September 2024, we conducted a prospective randomized study in the Department of Dermatology and Venereology of our institution to assess the melanin levels in hypopigmentation patches in vitiligo patients before and during treatment using mexametry, as well as on the surrounding healthy skin, to study the possibility of using this method as a control of response to therapy. A total number of 17 patients (10 women and 7 men) aged 18–70 years with non-segmental stable vitiligo were included in the study. The study was carried out on the device “Soft Plus.” The principle of mexametry is based on the ability of the skin to absorb light. Since melanin absorbs light in a wide range of wavelengths from ultraviolet to infrared, a special hand-held sensor-measurer conducts light waves in the green (λ = 568 nm ± 3 nm), red (λ = 660 nm ± 3 nm), and infrared (λ = 870 nm ± 10 nm) spectra. The wavelength is selected to match the spectral absorption peak of melanin.

Measurements were performed in 19 localizations: On the face (forehead, eyelids, lips, chin, cheeks, and neck); on the trunk (chest, axillae, back, buttocks, and groin folds); on the upper extremities (shoulders, elbows, forearms, and back of hands); and on the lower extremities (thighs, knees, shins, and back of feet). Measuring ranged from 0 to 100 units (u.u.) were taken in the same area before the start of treatment and after 3 months of combined therapy by determining the average. The lesion area relative to the body surface area before and after therapy was evaluated using the vitiligo extent score (VES) on a vitiligo calculator.

All 17 patients received the same treatment protocol: Microneedling procedure once per week, NB-UVB (311-nm) 3 times/week. The course of treatment was administrated in two courses of 20 sessions during 7 weeks, with a 4-week apart (18 weeks in total). Microneedling was followed by topical application of 5% 5-fluorouracil. NB-UVB (311-nm) was performed on the same days as microneedling.

The response rate to treatment in different body parts also based on the G score is visual analogue repigmentation scale (G0–G4): G0-no response, G1-poor response (0–25% repigmentation), G2-good response (25–50%), G3-very good response (50–75% repigmentation), and G4-excellent response (repigmentation >75%).

Melanin levels increased in vitiligo patches according to mexametry 3 months after therapy, especially in the elbows – from 2.1 u to 13.4 u, back of hands – from 1.4 u to 17 u, and knees – from 5.5 u to 18 u. For more detailed information about melanin concentration in each area, you can look up Table 1. In the same areas, lower VES values were recorded from 2.36% to 24.8% before treatment to 1.13–18.2% after 3 months of treatment. The increase in melanin levels according to mexametry correlated with categories: G4 and G3 were observed in these areas on a visual analogue scale of repigmentation. Although VES provides a subjective estimation that depends on clinical experience, on the other hand, mexametry offers a standardized, objective method for measuring pigmentation changes. The observed strong equivalent outcomes between mexametry and VES scores do not diminish the justification for this study. On the contrary, this alignment reinforces the validity of mexametry and highlights its potential to complement VES. Thus, the observed concordance with VES serves to validate, rather than undermine, the utility of mexametry in clinical trials.

This study demonstrates that mexametry is a reliable and objective method for monitoring repigmentation in vitiligo. It allows for digitized, quantitative tracking of treatment response. Further studies are needed.