Copolyamide hydrophilic gel fillers have been used off-label for breast soft-tissue augmentation. Composed of approximately 98% saline and 2% copolyamide polymers, these fillers provide a minimally invasive and relatively low-cost alternative to surgery [1]. In Korea, due to increasing safety concerns, the Korean Society for Aesthetic Plastic Surgery issued a position statement advising against the use of Aquafilling for breast augmentation until its long-term safety could be confirmed [2]. Delayed complications, such as firmness, nodularity, asymmetry, filler migration, and infection, have been increasingly reported in the literature [3–7]. Although regional migration of copolyamide fillers has been documented [7], systemic dissemination resulting in multifocal abscess formation across several anatomical compartments is rare. Previous reports have described distant filler migration to the lower abdomen after mammographic compression without associated infection [8]. In contrast, the present case involved extensive soft-tissue involvement with recurrent abscesses affecting the thoracoabdominal wall, perineum, and anterior mediastinum, requiring repeated surgical drainage and prolonged systemic antibiotic therapy.

A 26-year-old woman presented with gradually worsening swelling and tenderness in the lower abdomen and perineal region (Fig. 1). Seven years earlier, she had undergone bilateral breast augmentation with an injectable filler composed of copolyamide gel mixed with autologous blood. One year before presentation, she received an additional hyaluronic acid filler injection to the medial aspect of each breast. She described recurrent swelling in the lower abdomen and vulvar area for 2 years, which had acutely worsened during the 2 weeks before presentation. Magnetic resonance imaging performed at an outside hospital revealed foreign material with peripheral enhancement and soft-tissue infiltration involving the left lateral abdominal wall, inguinal region, and perineum. Additional lesions were noted in the anterior thoracic wall and back (Fig. 2). These findings were interpreted as filler migration with secondary infection. Laboratory evaluation showed a mildly elevated C-reactive protein (CRP) level of 1.62 mg/dL.

One month after the initial visit, the patient underwent surgical management under general anesthesia, including ultrasound-guided liposuction of the breast and abdominal areas to remove filler material and associated fluid collections. Approximately 600 mL of grayish fluid was aspirated from the breast, lower abdomen, and vulvoperineal regions. Subsequent serial outpatient aspirations yielded an additional 315 mL of fluid, including a substantial amount from the vulvar area.

Four months after the initial visit, the patient developed new-onset swelling and pain in the same region following an upper respiratory illness. Initial aspiration drained 415 mL of fluid, and empiric oral cephalexin was prescribed. However, her symptoms rapidly progressed. Four days later, she presented to the emergency department with worsening swelling and tenderness of the left abdominal wall, and 510 mL of fluid was aspirated (Fig. 3). Inflammatory markers were markedly elevated (CRP, 18.25 mg/dL; procalcitonin, 0.65 ng/mL), although blood cultures and methicillin-resistant Staphylococcus aureus screening were negative. Contrast-enhanced computed tomography (CT) demonstrated multifocal abscesses in the thoracoabdominal wall and perineum, as well as encapsulated fluid extending into the anterior mediastinum (Fig. 4). She was admitted to the Infectious Disease Service, and broad-spectrum intravenous vancomycin therapy was initiated. After admission, approximately 700 mL of fluid was aspirated.

Although the patient’s systolic blood pressure transiently decreased to 99 mmHg, her Sequential Organ Failure Assessment (SOFA) score was 1, and she did not meet the Sepsis-3 criteria. The patient was subsequently transferred to our department for surgical intervention. Five months after presentation, debridement and irrigation of the affected areas were performed under general anesthesia, and approximately 630 mL of purulent fluid was evacuated intraoperatively. The patient’s condition steadily improved postoperatively. Her CRP level declined to 2.36 mg/dL on postoperative day 2 and to 0.62 mg/dL at discharge, at which time she was transitioned to oral moxifloxacin.

During outpatient follow-up (approximately 6 months after the first visit), her inflammatory markers normalized. However, she continued to experience intermittent swelling in the vulvar and groin regions. About 7 months after presentation, additional aspirations were performed, yielding serous fluid without overt signs of infection. One month later, follow-up CT showed interval improvement in abscesses of the right chest and left abdominal walls, along with resolution of a small reactive pleural effusion (Fig. 5). After consultation with the thoracic surgery team, continued observation was recommended, given the absence of systemic infection or compressive symptoms. The patient has since remained asymptomatic without recurrence and continues to undergo close clinical follow-up (Table 1).

Aquafilling and other copolyamide gel fillers have been used for breast augmentation despite lacking regulatory approval and formal safety evaluation [2]. The hydrophilic and non-biodegradable nature of these gels allows them to persist in tissues for years, increasing the potential for delayed complications [7,9]. Previous studies have documented various adverse outcomes associated with copolyamide fillers, including chronic inflammation, granuloma formation, filler migration, and abscess development (including galactocele formation in postpartum patients) [3,6,7]. Namgoong et al. [7] reported that induration or palpable masses occurred in more than 80% of patients treated for Aquafilling complications, with infection-related problems affecting a considerable subset. Even in the absence of overt clinical symptoms, histopathological analyses revealed inflammatory cell infiltration surrounding the injected filler [4]. Moreover, improper injection techniques—such as injecting a large volume without ultrasound guidance—have been implicated in unintended filler misplacement and subsequent complications [10].

This case is remarkable due to the progressive multifocal spread of infected filler across multiple anatomical compartments, including the unusual extension into the anterior mediastinum. Additionally, the copolyamide filler was mixed with autologous blood at the time of injection—a combination not previously reported in the literature. Although a direct causal mechanism cannot be confirmed, we hypothesize that the inclusion of autologous blood may have served as an inflammatory priming factor, amplifying local inflammatory responses and promoting subsequent filler dissemination. Such extensive migration with recurrent abscess formation is exceedingly rare, although a recent report described a patient who developed sepsis secondary to an Aquafilling-related breast abscess 6 years post-injection [11]. In the present case, the cumulative fluid volume drained across multiple interventions exceeded 3.0 L, reflecting a combination of residual gel filler, inflammatory exudate, and purulent material. The persistent inflammatory nidus likely resulted from the filler’s non-absorbable nature and may have been aggravated by the patient’s additional hyaluronic acid filler injection or by intercurrent infection. Similar studies have shown that the coexistence of other augmenting materials can provoke inflammatory reactions and complicate clinical management [5,12].

The latency period for Aquafilling-related complications is typically between 5 and 8 years post-injection [7,11,13]. This delayed presentation aligns with the slow degradation and chronic inflammatory behavior of copolyamide gels. In our case, the patient developed symptoms approximately 7 years after the initial procedure, consistent with prior reports.

The management of Aquafilling-related complications is challenging and often requires a multimodal approach [13]. Because no standardized treatment guidelines exist, management should be tailored to the patient’s clinical presentation. Minimally invasive procedures—such as image-guided aspiration or liposuction—can help debulk the filler and relieve symptoms [3]; however, definitive treatment frequently necessitates surgical removal of residual gel deposits. Adjunctive methods, including waterjet-assisted liposuction, have been reported to facilitate more complete removal of Aquafilling material from affected tissues [14]. When infection is suspected, broad-spectrum antibiotics are indicated; however, cultures are often sterile, and antibiotic selection remains empirical. In this case, vancomycin (for resistant gram-positive coverage) and moxifloxacin were used due to negative cultures but high clinical suspicion of persistent bacterial infection. Close collaboration among plastic surgery, infectious disease, and thoracic surgery teams was critical, given the mediastinal involvement and need for continued surveillance for new fluid collections.

Notably, similar late complications have been reported with other permanent fillers. For example, a 10-year review of polyacrylamide hydrogel breast injections—a precursor injectable gel used abroad—described numerous cases of severe long-term complications necessitating surgical intervention [15]. This case highlights the importance of thorough patient counseling and long-term follow-up after any off-label filler procedure. Patients should be clearly informed that serious delayed complications, including migrating abscesses and potentially life-threatening infections, can occur years after treatment. Clinicians should maintain a high index of suspicion when evaluating patients with a history of filler injection who present with unexplained soft-tissue swelling, pain, or inflammation. Early imaging and a multidisciplinary approach are essential for timely diagnosis, management, and prevention of systemic sequelae.

One limitation of this report is that the filler material was a nonstandard mixture of copolyamide gel and autologous blood, making it difficult to verify its precise composition and immunologic characteristics. The proposed role of autologous blood as an inflammatory priming factor remains speculative, as no histopathologic confirmation was obtained. Further research is needed to elucidate the biological behavior of such mixed materials.

Despite this limitation, this case illustrates a rare but severe complication of copolyamide breast filler injection, leading to extensive soft-tissue involvement and multifocal abscess formation, including anterior mediastinal extension. Although overt sepsis was not observed, the patient experienced a prolonged and complex clinical course requiring repeated aspirations, multiple surgeries, and long-term antibiotic therapy. The unpredictable nature of permanent fillers and the substantial morbidity associated with their complications underscore the need for extreme caution in their use. Long-term follow-up and coordinated multidisciplinary management are essential for early recognition and prompt treatment of delayed adverse events.