Background: Hyaluronic acid and calcium hydroxylapatite fillers are generally safe, efficacious, and well tolerated. However, complications are inevitable, as with any medical procedure. Nodules at the site of filler implantation may pose the greatest challenge, as treatment is often empiric and can be influenced by misconceptions.
Methods: Hyaluronic acid and calcium hydroxylapatite filler nodules, with or without inflammation, may form at various times during and after injection. The probable causes of these complications are described. Clinicians can benefit from a problem-oriented approach to their diagnosis and management. The need to consider common causes—notably, infection—before rare ones, such as hypersensitivity to filler material, is discussed.
Results: Better understanding of the possible causes of hyaluronic acid and calcium hydroxylapatite filler nodules effectively guides treatment and prevents underestimation of the role of contamination—including mycobacteria—in the pathogenesis of inflammatory nodules. It can also inform preventative strategies. The authors advocate ultrasonographic imaging for patients with persistent nodules, to help determine the precise nature and location of the implanted materials.
Conclusions: When used appropriately, hyaluronic acid and calcium hydroxylapatite fillers have low complication rates. Filler nodules are often treated without full evaluation of possible causes. A problem-oriented approach that does not overlook the most common causes could improve the outcome of these unfortunate events and help prevent their occurrence and/or recurrence. Complications from currently available hyaluronic acid and calcium hydroxylapatite fillers are typically related to aspects of the injection procedure, such as suboptimal technique and bacterial contamination, rather than to the products themselves.