Impact and associates of digital pitting in patients with systemic sclerosis: a pilot study

Objective: Despite being a cardinal clinical sign of systemic sclerosis (SSc), digital pitting has been little studied. Our objective was to test, in a pilot study, the hypothesis that pitting is painful and associated with digital vascular disease severity.Method: Fifty patients with SSc were recruited: 25 with and 25 without digital pitting. Fingertip pain was assessed on a 0-10 scale. Thermography of both hands assessed surface temperature, allowing calculation of the distal-dorsal difference (temperature gradient) for each finger. Nailfold capillaroscopy was performed in each finger using a dermatoscope, and graded on a 0-3 scale (0 = normal; 3 = grossly abnormal).Results: In the 25 patients with digital pitting, 65 fingers in total were affected (mainly the index and middle fingers). Pain scores were higher in 'pitting' patients [median 4 (interquartile range 3-8) vs 0 (0-2), p < 0.001], and pitting patients reported that pitting impacted on activities of everyday living. Temperature gradients along the fingers did not differ significantly between patients with and without pitting (p = 0.248). Pitting patients were more likely to have 'grossly abnormal' capillaries than those without pitting, and less likely to have 'no/mild' nailfold capillary changes.Conclusions: Digital pitting is painful and impacts on hand function. Capillaroscopy findings provide further support for an association between pitting and severity of digital vascular change. Larger, more comprehensive studies are required to examine the pathophysiology of pitting and to pave the way to therapeutic intervention, ideally including preventive strategies.