Frequency and Characteristics of Delayed-Onset Inflammatory Nodules After Hyaluronic Acid Injections in Japan.

Background: No studies in Japan have investigated delayed-onset inflammatory nodules as an adverse event following hyaluronic acid (HA) injections. Our institution, located in a rural area with no nearby aesthetic clinics, allows for comprehensive follow-up of HA-treated patients. This study analyzed complications from 673 cases over 6 years, focusing on delayed-onset inflammatory nodules.

Methods: A retrospective review of medical records was conducted for patients treated with AbbVie-Allergan HA products between January 2018 and December 2023. Adverse events were categorized as acute complications or delayed-onset inflammatory nodules. Statistical analysis assessed product type, time to onset, patient history, and treatment approaches.

Results: One acute allergic reaction and seven cases (1.07%) of delayed-onset inflammatory nodules were identified. Volbella was involved in 4 cases, Volift in 1 case, Voluma in 1 case, and Ultra Plus in 1 case. Statistical analysis revealed a significantly higher incidence with Volbella (p = 0.0484). The average onset was 144 days, with no seasonal pattern. Among affected patients, three had a history of non-HA-related allergies, and one had a preceding infection. Treatments included oral antibiotics (2 cases), oral antihistamines (5 cases), topical steroids (3 cases), hyaluronidase injections (4 cases), oral steroids (2 cases), and surgical intervention (1 case).

Conclusions: Delayed-onset inflammatory nodules occurred in approximately 1% of cases, with Volbella showing the highest incidence. Patients with allergies or prior infections may have an increased risk. Comprehensive informed consent should emphasize potential delayed complications to ensure patient understanding.

Level Of Evidence Iv: This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .