This patient is a 30-year-old Chinese male with Fitzpatrick Skin Type IV and a hypertrichotic BN that had gradually spread across almost his entire right face since puberty. Prior to our intervention, he had undergone several laser treatments, including the Q-switched 755 nm laser and CO2 ablative laser with minimal improvement and obvious adverse events, such as hypopigmentation and scarring (Fig. 2a). Significant improvement was seen in the lesions after 21 LFQS 1064 nm laser treatments (Fig. 2b). Then the patient underwent 21 subsequent LFQS 1064 nm laser treatments with 5 sessions of LP Nd: YAG laser depilation. Encouragingly, more than 75% of the lesions were eliminated and it is important to note that our treatment avoids the depigmented part of the lesion, which fortunately improves spontaneously (Fig. 2c). This patient had a satisfaction score of 5.

Representative photographs of Case 2. (a) Before treatment (hypopigmentation and scarring on the surface of the lesion remaining after several unsuccessful treatments in other hospitals); (b) Two weeks after 21 sessions of LFQS 1064 nm laser and before laser depilation; (c) Two weeks after 41 sessions of LFQS 1064 nm laser and five sessions of LP 1064 nm laser

Previous studies have indicated that the conventional high-energy and small-spot QS 1064 nm laser therapy for BN fell far short of expectations [2]. And LFQS 1064 nm laser is effective in treating various pigmentary diseases with minimal side effects [3]. Our clinical practice showed two patients with BN achieving significant improvement with LFQS 1064 nm laser treatments. The reason may be that the LFQS 1064 nm laser can effectively treat hyperpigmentation by causing only the fragmentation of melanin granules and reducing the number of melanosomes through subcellular-selective photothermolysis without destroying the cells [4]. Meanwhile, short wavelength lasers can significantly damage keratinocytes, leading to the release of cytokines and inflammatory factors, which promotes the production of melanin and leads to recurrence [5, 6]. The long wavelength LFQS 1064 nm laser can protect keratinocytes, which may explain for the low recurrence rate of lesion.

In our two cases, the LFQS 1064 nm indeed demonstrated a mild improvement in hair overgrowth, but to meet patients’ expectations, we also applied LP Nd: YAG laser to alleviate hypertrichosis. No side effects or relapses were observed during our treatment, further suggests that LFQS 1064 nm laser could serve as a novel effective and safe therapeutic option for BN resistant to other lasers.