Hyaluronidase for Sclerodactyly in Systemic Sclerosis Trial (HASSc)

Systemic sclerosis (SSc) is a chronic autoimmune disease characterized by progressive fibrosis of the skin and internal organs. Sclerodactyly, a key manifestation, results in skin thickening, joint contractures, reduced digital range of motion, and significant functional impairment. There are currently no effective localized therapies to improve hand mobility in affected patients.

Hyaluronidase is an enzyme that degrades hyaluronic acid within the extracellular matrix and is widely used in dermatology with a well-established safety profile. Emerging evidence suggests that reduced endogenous hyaluronidase activity in SSc may contribute to impaired matrix turnover and persistent fibrosis. Intradermal hyaluronidase has demonstrated preliminary efficacy in improving tissue flexibility in SSc-associated microstomia, supporting its potential as a localized antifibrotic therapy.

This pilot study will evaluate the feasibility, safety, and preliminary efficacy of serial intradermal hyaluronidase injections for SSc-associated sclerodactyly. In an open-label, prospective design, 10 participants will undergo monthly treatment of two affected digits over 28 weeks. Outcomes will include change in digital range of motion measured by standardized goniometry and patient-reported hand function using the Cochin Hand Function Scale-6 (CHFS-6). Feasibility and safety will be assessed through recruitment, adherence, and systematic adverse event monitoring with predefined stopping criteria.

As an early-phase pilot, this study is not powered for hypothesis testing but is designed to generate the data necessary to inform a "go/no-go" decision for future trials. Results will provide critical estimates of feasibility, safety, and clinical signal to support the design of a subsequent randomized controlled trial and may establish a novel, localized therapeutic strategy for improving hand function in patients with systemic sclerosis.