Delayed-onset Nodules (DONs) and Considering their Treatment following use of Hyaluronic Acid (HA) Fillers.

Delayed-onset nodules (DONs) represent a poorly understood and generally neglected group of complications. It is not a diagnosis. The underlying pathologies and their incidences are largely unknown due to the lack of specificity in clinical signs and the challenges in accessing diagnostic tests, cost implications, or reluctance from patients to undergo them. A lack of presumptive clinical diagnosis, coupled with management ranging from "scatter-gun" polypharmacy to clinical inertia, is believed to result in chronicity and increased morbidity. This paper provides guidance on the identification and understanding of the underlying pathologies and encourages the increased utilization of a medical model of care. The more routine adoption of histopathology, inflammatory markers, and ultrasound will permit a more targeted management and a greater understanding of the incidences and evolution of the pathologies.