Calcium Hydroxylapatite‐Carboxymethylcellulose as a Treatment for Forearm Dermatoporosis: A Prospective, Delayed‐Start, Contralateral Case Series

BACKGROUND: Dermatoporosis is a chronic cutaneous fragility syndrome marked by dermal thinning, collagen loss, and recurrent purpuric lesions. Effective treatments remain limited. Calcium hydroxylapatite-carboxymethylcellulose (CaHA-CMC) is a regenerative biostimulator with demonstrated skin extracellular matrix-restorative effects, but its usefulness in forearm dermatoporosis has not been established. OBJECTIVES: To evaluate the efficacy, durability, and safety of hyperdiluted CaHA-CMC for reducing lesion burden, increasing dermal thickness, and enhancing collagen density in dermatoporotic forearms. METHODS: In this prospective, delayed-start, contralateral case series, six patients with bilateral dermatoporosis received a single treatment of 1:2 CaHA-CMC. The more clinically affected arm was treated at Day 0, and the contralateral arm served as a 45-day untreated control before receiving identical treatment. Lesion coverage was quantified from standardized photographs using an ImageJ-based workflow. Dermal thickness was measured by high-frequency ultrasound, and collagen content was assessed from Masson's Trichrome-stained punch biopsies. Early effects (Day 0-45) were evaluated using paired testing and a subject-level difference-in-differences (DiD) estimator. Durability was assessed by aligning post-treatment follow-ups by time-since-treatment (TST), focusing on TST45 and an ~1-year window (320-365 days). RESULTS: From Day 0 to Day 45, lesion coverage decreased in treated forearms from 5.60% ± 4.47% to 1.92% ± 2.07% (p = 0.041), while changes in untreated contralateral forearms were not significant. In pooled participant-level analyses aligned by post-treatment timing, lesion coverage decreased from 4.27% ± 1.88% at baseline to 1.16% ± 1.10% at TST45 (p = 0.0313) and remained reduced at the ~1-year window (1.14% ± 0.68%, p = 0.0313), corresponding to a 73.4% reduction at ~1 year. Collagen area increased by 69.7% at 45 days post-treatment (p = 0.0009), and dermal thickness increased by 36.05% (p = 0.0007). Treatment was well tolerated; one transient nodule resolved with massage. CONCLUSIONS: A single session of hyperdiluted CaHA-CMC produced rapid and durable clinical, histologic, and ultrasonographic improvement in forearm dermatoporosis. Findings warrant further evaluation in larger controlled trials.