Erythema measurements may allow early diagnosis of diabetes mellitus in adult psoriatics

ABSTRACT Background We have observed that the erythema in subjects with psoriasis vulgaris associated with non‐insulin‐dependent diabetes mellitus (NIDDM) presents a mostly deep‐red to purple hue instead of the typical pink to red tones. We carried out a descriptive clinical study, including 141 patients with psoriasis vulgaris to quantify these colour differences. Methods Mean erythema index values were established for the psoriatic plaques of adult subjects using an optoelectronic method. Non‐diabetic psoriatics underwent an oral glucose tolerance test (OGTT), and based on the results of the oral OGTTs, the subjects were divided into three groups: 18 psoriatics with NIDDM, 16 psoriatics with impaired glucose tolerance (IGT) and 107 psoriatics with normal glucose tolerance. The mean erythema index value was calculated for each group and the findings were compared. Results The differences in the erythema were found to be highly significant between the group of subjects with psoriasis having normal glucose tolerance and both those with IGT and those with NIDDM (P