When Hyaluronic Acid Alters its Rheology: Clinical, Ultrasonographic and Pathological Correlation

Abstract

Hyaluronic acid has demonstrated itself as a highly successful non-invasive medical procedure for mitigating facial aging changes. This success is primarily attributed to its biodegradable or temporary nature, the reproducibility of aesthetic results, and the potential for dissolution through hyaluronidase. Despite its virtues, changes in the rheology of the product can occur, leading to alterations in its structure, resulting in the formation of visible, palpable nodules that are challenging to degrade with hyaluronidase. We present a case series of 9 patients in whom high-resolution ultrasound detected changes in the normal echographic appearance of hyaluronic acid suggestive of pseudosolidification, including increased echogenicity, a hyperechoic band inside the periphery of the deposits, the absence of degradation changes, and persistent, well-defined oval morphology. All cases showed no inflammatory activity on Doppler. In one case, the deposit was surgically removed during blepharoplasty, and histopathological analysis provided useful information to understand the mechanisms behind such complications.