## 1 Introduction  
Since the advent of HIV antiretroviral therapies at the end of the 20 th century, the morbidity and mortality rates associated with HIV infection have decreased dramatically [1, 2]. Unfortunately, these benefits are associated with substantial morphologic changes in the body, such as abnormal fat distribution with peripheral lipobyperthrophy (gynecomastia, buffalo hump, etc.) and facial wasting, as well as potential systemic adverse effects. Facial lipoatrophy, defined as flattening or indentation of normally convex facial contours, is the major stigma for human immunodeficiency virus-infected people [3, 4]. It can have dramatic effects on their self-esteem and socialization, and it may result in reduced antiretroviral adherence [5]. During the years, an increasing number of HIV patients receiving highly active antiretroviral therapy had medical consultations requesting an option to correct their resulting deformities, such as buffalo hump and facial wasting [6]. Surgical and non-surgical strategies have been introduced to restore facial features in the patient population. The use of peripheral hypertrophied fat to restore the facial lipoatrophy with lipofilling theoretically seems to be the best option. In fact, during the same operation not only can facial wasting be treated, but body contouring procedures can also be performed [7; 8]. On the other hand, not all patients present both facial lipoatrophy and body lipobhypertrophy. Moreover, as for the procedures performed only for cosmetic purposes, not all patients are prone to a surgical approach [9; 10]. The request for non-surgical aesthetic procedures has increased during the last 20 years. Statistics released by the American Society for Aesthetic Plastic Surgery in 2016 showed a dramatic increase in surgical and non-surgical cosmetic procedures throughout the preceding 20 years [11]. The number of plastic surgery procedures doubled from 1995 to 2015 and the quantity of non-surgical cosmetic procedures increased by 12-fold, which demonstrates that an increasing number of subjects are seeking cosmetic improvements and that non-surgical procedures are preferred over surgical interventions [10]. Aesthetic procedures to improve facial wrinkles and folds have been widely described in the literature: filler injection has been among the most frequently used treatments in facial recontouring, restoring a smoother and more youthful looking appearance [12]. Hyaluronic acid (HA) filler is an attractive substance to be used as filler, which is because of its features such as the ability to bind to large amounts of water and the natural presence of HA in the skin. It is synthesized on cell membrane of fibroblasts and keratinocytes, and also plays an important role in skin hydration facilitating cellular movement in inflammation and wound healing and its decrease is associated with skin aging [12; 13]. HA injection was the second most popular nonsurgical cosmetic with a 60% increase from 2014 to 2018 and this could be explained by its affordability, minimal downtime, immediate results, minimal invasiveness and good safety profile, deriving from the feature that HA can be dissolved easily with hyaluronidase in case of complications [14]. Deep injections may yield an enduring result: [PERSON] demonstrated that semi-permanent volumizing effects can be achieved if the target area has an underlying bony floor, hypothesizing that periosteal stem cells, activated by HA, potentiate the volumizing effect [15]. Calcium hydroxyapatite (CaHA)filer is an injectable, biocompatible, nontoxic, non-irritating and nonantigenic material composed of synthetic calcium hydroxyapatite microspheres suspended in an aqueous carrier gel [16]. In 2006, its use was approved by Food and Drug Administration for the restoration and correction of the signs of lipoatrophy in individuals with HIV. After injection, the carrier gel is gradually absorbed and the CaHA particles remain.