Clinical and Dermoscopic Features of Subungual Hemorrhage: A Retrospective Study of 420 Cases

Subungual hemorrhage (SH) may be difficult to distinguish from nail unit melanoma, onychomycosis, and other nail disorders. Dermoscopy enables non-invasive visualization of subtle subungual structures and provides useful information for differential diagnosis. This study aimed to analyze the clinical and dermoscopic features of SH and explore their associations with lesion location, disease course, and nail involvement.

Clinical and dermoscopic data of 420 patients diagnosed with SH between December 2018 and March 2024 were retrospectively collected from two tertiary hospitals in China.

Patients aged 18-45 years accounted for 65.5% of the cohort, and 84.3% of lesions were located on the toenails. Most patients (69.5%) had a single lesion, and 73.8% and 79.3% showed no nail margin involvement or nail plate damage, respectively. Toenail involvement was more frequent in female (p = 0.003) and young adult (p = 0.002) patients. The predominant dermoscopic features were purplish-red/black pigmentation (72.9%), irregular morphology (71.0%), and linear or striated pseudopods surrounding the lesion (56.7%). Irregular morphology was significantly more frequent in toenail lesions, whereas linear morphology was more common in fingernail lesions (both p < 0.001). Irregular shapes were predominant (73.6%) in cases with a short-term course (< 3 months), whereas linear lesions accounted for 31.6% of lesions in patients with a long disease course (≥ 12 months). Lesion morphology was significantly associated with disease course (p < 0.001). Irregular morphology was also significantly associated with nail margin involvement (p < 0.001) and nail plate damage (p = 0.007), while linear or striated pseudopod lesions showed a significant association with nail margin involvement (p < 0.001).

In this cohort, SH predominantly affected females and young adults and typically presented as a single toenail lesion. Dermoscopic features of SH varied according to lesion location and disease course, and irregular morphology was associated with nail margin involvement and nail plate damage. Recognition of characteristic dermoscopic features, together with clinical history and lesion evolution, may facilitate differentiation of SH from nail unit melanoma and other nail disorders, help avoid unnecessary biopsy in typical cases, and prompt further evaluation of suspicious lesions.