Amplitude of the thermal hyperhemia in systemic sclerosis (SSc) and rheumatoid arthritis. (a) Patients with systemic sclerosis (SSc), primary Raynaud's phenomenon (RP) and healthy controls. (b) Patients with rheumatoid arthritis (RA) and primary RP. Data are expressed as box plots in which 50% of values lie within the box. The horizontal line depicts the median value and the whiskers indicate the 10th and the 90th percentiles of all values.