Ultrasonography reveals nail thickening in patients with chronic plaque psoriasis

Nail psoriasis is usually investigated and diagnosed by clinical examination. Ultrasonography is a non-invasive imaging technique for studying soft tissue involvement. The objective of this study was to estimate nail involvement in patients with chronic plaque psoriasis by ultrasonography. Prevalence, clinical type and severity of nail involvement according to nail psoriasis and severity index (NAPSI) were investigated in 138 patients with psoriasis. The thickness of the plate and bed of the fingernails was measured in 54 patients with psoriasis, 46 healthy controls and 37 patients with chronic eczema, using an ultrasonographic system equipped with a frequency transducer of 18 MHz. The prevalence of nail psoriasis was 73 % (102 out of 138). Onycholysis and thickening of the nail plate were the most common clinical type affecting 56 and 50 % of patients, respectively; splinter haemorrhages was the less common involving 10 % of patients. The mean NAPSI score was 18.4 ± 17.5 (SD; range 0-107). The thickness of fingernail plate and bed was significantly higher in patients with psoriasis with nail disease compared to healthy controls and patients with chronic eczema (p < 0.001). There was a linear correlation between NAPSI and plate and bed nail thickness (r = 0.52 and r = 0.38, p = 0.001). Increased nail plate and bed thickness was observed also in patients with psoriasis without clinically apparent nail involvement. In conclusion, thickening of the nail is a common feature of nail psoriasis also in patients without clinically apparent nail involvement.