Given the stability of gold and the ease of the procedure, gold thread rejuvenation therapy is often performed for skin care treatments such as skin rejuvenation. Importantly, gold therapy has been reported an effective treatment for the improvement of the appearance of the aging skin such as the elimination or reduction of facial wrinkles and improvement of skin elasticity. However, despite its noted efficacy, many side effects have been reported as well1. Here, we describe a case of macular pigmentation caused by using low fluence neodymium-doped yttrium aluminum garnet (Nd:YAG) laser (1064 nm) after gold thread implantation was performed for facial rejuvenation.

A 47-year-old female patient presented with asymptomatic brownish macules on her left cheek, which had persisted for one year. She had a history of gold thread insertion performed for a facial skin lift at these sites six years ago. In addition, low fluence (3 J/cm²) Nd:YAG (1064 nm) laser procedures were performed three times for facial skin toning at a local clinic. She felt some transient burning sensation shortly after the laser procedures and soon discovered pigmentation on the face. The number and size of the lesions remained almost constant afterwards. Physical examination revealed multiple, unilaterally distributed, well-demarcated round-shaped, firm, varying degrees of brownish macules on the left cheek (Fig. 1A, B).

Histopathological examination of the cheek revealed golden-brownish rod-shaped foreign material and some fine golden granules in the deep dermis (1.4 mm) that was suspected to be gold. There was little inflammatory reaction around the substance, although there was some fibrosis and collagen bundle enlargement. Additionally, there was no evidence of granuloma (Fig. 2A, B).

Gold has long been regarded as a safe and stable metal when in contact with skin and mucosal membranes2. Therefore, due to these non-allergic, non-infective, chemically stable characteristics, it has been widely used as dental filling material, as accessories which directly attach to the skin, and various other medical uses, including cardiac coronary artery stents. Since the first gold thread implantation was performed by Dr. Caux in France, with subsequent histologic changes in the skin confirmed by Adamyan and colleagues, gold thread rejuvenation has been frequently used for improving skin structure and appearance3. Furthermore, gold particles inserted into the dermis can stimulate collagen growth and angiogenesis of the surrounding area14.

In this case study, the Nd:YAG laser was initially thought to be the causal factor for the macular pigmentation given the seemingly immediate occurrence following the procedure. Although the Nd:YAG laser can cause post-inflammatory hyperpigmentation, no pigmentary incontinence or severe dermal inflammation was observed when the patient's biopsy was examined histologically. In addition, these lesions only appeared at the sites of previous gold thread implantations, and not in areas where she had undergone whole laser treatment.

In the six years after the gold thread insertion procedure and the appearance of the hyperpigmentation, there was no presence of any granuloma or severe inflammation in the dermis as seen by histology. Considering these points, her symptoms may not have arose as a result of a latent foreign body reaction to the gold itself nor from allergic contact dermatitis to the gold2456.

Therefore, we surmised that these lesions were not simply a response to the gold itself, but there may be a correlation between the laser's specific wavelength to the presence of the gold. Among the papers that have reported on the wavelength of the laser, Xing et al.7, concluded that the 1064 nm Nd:YAG laser could change the shape of gold. Surface melting of gold and the morphologic changes from rod to sphere occurs when gold nano-rods encounter high laser energy density nanosecond Nd:YAG laser (6~14 J/cm²). As the frequency of laser radiation increases, the likelihood of change may increase. Given this phenomenon, it is conceivable that the repeated Nd:YAG laser procedures might change the surface or the shape of the pre-inserted gold coated polydioxanone thread, triggering pigmentary changes on the face. Here, the patient underwent three such laser procedures which multiple-passes technique is usually used for skin toning8. The fact that no further developments or changes were observed after laser therapy also reduced the possibility of other causes. In 2009, a case of paradoxical darkening of tattoo ink after low fluence (2 J/cm²) 1064 nm Nd:YAG was reported that the interaction of ferric oxide and the laser is presumed to be the causative for the of the darkening8. It empowers our opinion that the interaction of the laser and the pre-inserted material in the skin is a key factor to the pigmentation. We note that further cases and in vivo experiments on the interaction between gold and the Nd:YAG laser are warranted to support this view.

Gold, which was considered relatively safe in the past, but has recently been reported to have side effects in the body such as allergic gold dermatitis and pseudolymphoma256. Allergic gold dermatitis may present as chronic eczematous papules, which have severe dermal involvement histologically2. Pseudolymphoma caused by gold, which is not uncommon in Asian countries may exhibit a benign course with microscopic appearance that resembles cutaneous lymphoma5. However, to our knowledge, this is the first case of skin lesions presenting as brownish macular eruptions caused by the addition of Nd:YAG laser procedures following gold thread insertion.

Recently, gold thread rejuvenation and laser therapy have been performed frequently to meet the demands of the growing interest in cosmetic therapies and the skin industry. Although gold or laser treatments alone may have minor known side effects, physicians should be aware of the possibility of interactions that may occur with gold and Nd:YAG laser that can lead to irreversible skin damage as well as potentially irreversible sequelae.