Characterization of acne-prone skin with reflectance confocal microscopy and optical coherence tomography and modifications induced by topical treatment and probiotic supplementation

The evaluation of acne-prone skin and absent-to-mild acne is difficult because this condition is not associated with a clinically definable situation. Previous studies showed that apparently healthy skin in patients with previous episodes of acne shows microcomedos and infundibular hyperkeratosis upon reflectance confocal microscopy (RCM) evaluation. Our aim was to characterize the subclinical and microscopic characteristics of acne-prone skin by means of RCM and dynamic optical coherence tomography (D-OCT) and evaluate microscopic changes induced by treatment. A group of 20 patients received a daily combined treatment over a period of 3 months, consisting of probiotic supplementation with three strains of 109 colony-forming units of Lactobacillus (Lactobacillus reuteri, Lactobacillus casei subsp. rhamnosus, Lactobacillus plantarum) and a combined topical product of azelaic and hydroxypinacolone retinoate (HPR). Clinical evaluations and non-invasive imaging acquisitions using VISIA® System, RCM, and D-OCT were performed at baseline, and after 4 and 12 weeks. The total number of clinically evident non-inflammatory lesions decreased during treatment from 11.5 to 7.3 (p < 0.05). There was also an evident reduction in microscopic acne features at RCM and D-OCT, such as the number of small bright follicles, large bright follicles and vascular threshold density at 300 μm and 500 μm depths. The types and extent of microscopic alterations in acne-prone skin patients may not be evident by clinical scores. Patients with low investigator global assessment (IGA) grades are a heterogeneous population, characterized by different microscopic skin features. Acne-prone skin is susceptible to treatment, and RCM and D-OCT imaging are sensitive tools to objectively monitor subclinical skin changes.