Ehlers–Danlos syndromes (EDS) are inherited conditions that affect the body's connective tissue, which provides strength and support to the skin, joints, and blood vessels. People with EDS are often affected by stretchy skin, loose joints, and fragile tissues. Two common subtypes are classical EDS (cEDS) and hypermobile EDS (hEDS). While cEDS has an identifiable genetic biomarker, hEDS has no known genetic cause. Because diagnosis of hEDS depends entirely on physical exams, patient history, and ruling out other conditions, it can take more than ten years for patients to receive a confirmed diagnosis. Collagen, the main structural protein in connective tissue, is altered in both subtypes, but current laboratory methods for examining collagen are either not sensitive enough or too costly and complex for routine clinical use.
In a recent study by researchers in Toronto (Canada), scientists tested an optical method called Mueller matrix polarimetry to address this diagnostic gap. As reported in Biophotonics Discovery , the technique uses a microscope that shines polarized light through very thin, unstained skin biopsy samples, then measures how the light changes as it passes through. These changes reveal detailed information about tissue structure, including how much collagen is present and how well it is aligned. Unlike traditional staining or electron microscopy, this approach is label-free, relatively simple, and produces quantitative measurements that can be analyzed across samples.
The study included 19 participants: 3 healthy volunteers, 5 with cEDS, and 11 with hEDS. For each biopsy, the researchers recorded millions of polarization measurements and calculated 24 different parameters that describe how the tissue modifies polarized light. Several of these measurements—most notably linear polarizance (PL), β, and ψ—clearly distinguished healthy skin from EDS-affected skin. The team also found that five parameters (PL, rL, P1, P3, and Ptms) could differentiate classical from hypermobile EDS. These differences reflect variations in collagen organization that are not easily visible with conventional microscopy.
Although the study was small, it demonstrates that polarized‑light imaging can detect structural signatures of EDS in unstained biopsy samples, and it may even differentiate hEDS from cEDS and healthy tissue in a rapid, affordable, and quantitative manner. The researchers emphasize that larger, more balanced studies are needed before the method can move toward clinical use, but the findings point to a promising new avenue for objective evaluation of connective tissue disorders—especially for patients who currently wait years for answers.
For details, see the original Gold Open Access article by K. Tumanova et al., " Label-free differentiation of classical and hypermobile Ehlers–Danlos syndromes using Mueller matrix polarimetry ," Biophoton. Discovery 3(1), 015002 (2026), doi: 10.1117/1.BIOS.3.1.015002
