Professional tattoo removal with a sequence of three 1064-nm QS nanosecond-picosecond laser passes per session – one fractional mode, followed by two full-beam mode passes at 5-minute intervals, has shown to be an effective and safe treatment protocol to achieve almost full removal of dark and red tattoo inks in fewer sessions than single QS laser pass-per-session treatments [4]. According to the Kirby-Desai tattoo removal scale, which estimates the number of expected laser treatments required to achieve complete tattoo removal according to specific parameters such as patients skin phototype, tattoo anatomical location, colour, amount of ink, presence of scarring and/or tattoo layering, the approximate number of QS laser treatments to obtain complete tattoo fading in this clinical case would have been 11 [6]. However, utilising this innovative combination technique only 6 sessions were required for near complete tattoo fading (Fig. 2, image f).

However, overall outcome is significantly affected by post-treatment skin care regimes. An example of adaptive three stage post-laser skin repair protocol was described by L. Marini et al. in 2022 [4]. One of the most-important aims in effective post-treatment wound healing protocols includes the prevention of pathologic scarring, skin textural chromatic modifications and reduction of post-inflammatory hyperpigmentation.

Normal wound healing consists of four consecutive and overlapping phases [7]. Initially, during the haemostatic phase, clot’s formation alongside local accumulations of cytokines and chemokines attracting neutrophils, monocytes, and T-lymphocytes are the rule. The agglomeration of immune cells within wounded tissues initiates the inflammatory phase. The proliferation phase shortly follows and is characterised by the activation and migration of fibroblasts into wounded areas. Fibroblasts activate to produce neo-collagen, particularly collagen I and III, progressively reconstituting an efficient extracellular matrix. A portion of these activated fibroblasts differentiate into actin-containing myofibroblasts capable of contracting wounds. Simultaneously, epidermal basal cells also migrate to wounded sites and start to proliferate, initiating a re-epithelialisation process to resurface wounded skin. Finally, the remodelling phase induces progressive tissue normalisation and colour uniformity [7, 8].

Our patient developed eschar-like skin alterations one week after her first laser-tattoo removal session despite following precise post-operative skin care instructions. It can be presumed that this exaggerated skin reaction was due to a prolonged inflammatory phase following a set of moderately high laser parameters. Prolonged post-treatment inflammation leads to excessive neo-angiogenesis, fibrosis, and possible abnormal scarring [9]. In order to control this hyperactive inflammatory process, a pulsed regime of potent topical corticosteroids (clobetasol 0.05%) was applied. After approximately 30 days, as seen in the Fig. 1a and i, a complete re-epithelisation was achieved.

The rationale behind the use of pulsed topical application of class 1 corticosteroids is based on their anti-neoangiogenic and anti-inflammatory properties combined with a significant minimization of their tissue atrophying effects. These actions result in long-term beneficial tissue effects such as preventing or reducing PIH during the proliferating and remodelling phases of wound healing. Clinical photographs (Fig. 2b and f) demonstrate an overall successful healing process in the long-run.

Potential risk factors explaining the abnormal modification of post QS laser healing process observed in our case include a darker photogenetic skin type (Fitzpatrick III) and a previous history of PIH reported after a controlled cosmetic chemical peel. Literature confirms darker photogenetic skin type patients are more prone to develop hypo- and hyper-dyspigmentations following accidental or iatrogenic injuries [10]. These individuals are also at higher risk of developing hypertrophic scarring [10]. Additionally, heavily pigmented tattoos, with higher concentrations of localized superficial and deep dermal exogenous pigments, might be at risk of potential complications even if QS lasers are used. This is due to the photo-acoustic laser-tissue interaction in close proximity to the dermal-epidermal junction during the first tattoo removal sessions [11]. In our case, treated tattoo was highly pigmented and a fluence of 4 J/cm2, even if considered a relatively safe choice for majority of tattoos, might have been too aggressive, particularly when selected for the first tattoo removal procedure in a darker photo-genetic skin type patient.

Microscopically, the pathologic healing process observed in our patient may have triggered an abnormal, premature activation of myofibroblasts with a consequent, irregular retraction of wounded tissue leading to a less uniform tissue response. Eschar-like wound-healing alterations rapidly responded to continuous and intermittent topical class 1 corticosteroid treatment as demonstrated in Fig. 1c and e. Gradual reduction of topical corticosteroids made treated skin progress towards a smooth and chromatically acceptable skin complexion in 13 weeks.

In conclusion, this case demonstrated the importance of a thorough preliminary clinical evaluation of tattoos before planning a QS laser assisted tattoo removal procedure on which to base an appropriate choice of energy parameters. Dynamic clinical assessment of wound healing processes during early, intermediate, and late post-treatment times are of utmost importance to recognize early signs of abnormal skin repair and initiate properly tailored, personalized skin care regimes. The use of pulsed highly potent topical corticosteroids is an effective strategy to re-route abnormal healing processes towards more controlled skin repair. Personalized, controlled reduction of application frequency schedules has shown to progressively restore a normal healing process resulting in gradual improvement of skin texture and concomitant prevention of PIH.