Background Underweight patients develop Raynaud's phenomenon (RP) more frequently.  In a small study, skin temperature and perfusion in RP patients was positively associated with body mass index (BMI).  In clinical practice, we frequently observe an abnormal nailfold capillary microscopy (NCM) in underweight subjects with presumably primary RP, from which the implications are unknown.
Objectives The aim is to study whether being underweight is associated with the presence of more abnormalities on NCM.
Methods NCM, assessed by widefield videocapillaroscopy, was retrospectively assessed in consecutive patients with suspected RP. Patients were included when they had negative serology and did not develop any definite connective tissue disease or organ involvement after a maximum of 5 years follow-up. NCM pattern was classified as normal, non-specific, early, active or late, based on the Cutolo patterns. Weight and height were measured for clinical practice and patients were divided by BMI category: underweight (BMI<18.5 kg/m2), normal weight (BMI 18.5–25 kg/m2), and overweight (BMI >25 kg/m2). Dilated and giant capillaries were counted as well as the total number of capillaries.
Results A total of 352 patients were included (median age 40.6 years (24.9–52.9), male/female: 111/241), of which 47 were underweight, 220 normal weight and 85 overweight. Patients who were underweight presented more abnormalities (dilated capillaries, capillary loss or giant capillaries) on NCM, as shown in figure 1. BMI was negatively associated with NCM pattern, number of dilated capillaries and number of giant capillaries (r=-0.247, r=-0.225 and r=-0.221 respectively, all p<0.001) and positively with the total number of capillaries (r=0.260, p<0.001).
Conclusions In addition to well-known thermoregulatory abnormalities, clear NCM pattern abnormalities are more frequently observed in underweight patients with primary RP. BMI was negatively associated with the number of dilated capillaries and positively with capillary density. These data potentially suggest that damage to the microvasculature in underweight patients with primary RP may occur independently of the presence or development of a CTD and may be explained by other mechanisms.
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Disclosure of Interest None declared