Musculoskeletal and nail ultrasound findings in children with psoriasis: a case-control study

BACKGROUND: Children with psoriasis can develop juvenile psoriatic arthritis. Musculoskeletal ultrasound is a helpful imaging modality in the early recognition of joint inflammation. This pilot study aims to describe clinical and subclinical joint and nail abnormalities in children with psoriasis. METHODS: Children with psoriasis and healthy controls underwent ultrasound examination of various joints, entheses, and nails. Using a standard acquisition protocol, images were obtained in both B-mode and PD-mode. Differences between psoriasis and control groups were examined. RESULTS: Fifteen psoriasis patients who were not on systemic therapy and did not have clinical signs of arthritis and thirteen age- and sex-matched healthy controls were enrolled. While patients with psoriasis demonstrated subclinical synovitis in the finger, knee, and ankle joints more frequently than the control group (p = 0.047), no statistically significant difference was observed in the comparison of each specific joint. PD positivity was detected at the entheses in two patients with psoriasis and at three entheseal sites of two healthy children. Nail ultrasound examination demonstrated significantly thicker nail beds (1.6 vs. 1.4 mm, p < 0.001) and more frequent abnormal nail structure (70% vs. 21.2%, p < 0.001) in the psoriasis group compared to control group while the thickness of the nail plate and nail matrix were similar. Type II nail morphology changes were the most frequently detected type according to the Wortsman classification. Positive PD-mode findings in the nail bed and nail matrix were more common in the control group (both p < 0.001). Among the psoriasis cohort, nails with abnormal exam findings had significantly thicker nail plate (0.4 vs. 0.35 mm, p = 0.003) and nail bed (1.8 vs. 1.6 mm, p = 0.006) measurements compared to nails with normal examination. CONCLUSIONS: Ultrasound is a useful tool for evaluating inflammatory joint and nail findings that may help delineate subclinical joint inflammation in children with psoriasis.