PREVALENCE AND SIGNIFICANCE OF ACANTHOSIS NIGRICANS IN CHILDREN AND ADOLESCENTS

Acanthosis nigricans (AN) develops commonly in obese adults, yet its p revalence and metabolic significance in children and adolescents have not been determined. To address these issues, 100 obese children and a dolescents enrolled in the obesity clinic al the Royal Hospital, Musca t, Oman, were chosen at random and examined. AN was observed in 43 of the study children (43%). The frequency and severity of AN increased s ignificantly with increasing body mass index (BMI) in these children. Twenty patients with obesity and AN and 20 age-matched nonacanthotic o bese children, randomly selected from the study children, were investi gated. Their oral glucose tolerance and serum C-peptide responses to I V glucagon were evaluated. Circulating concentrations of fret thyroxin e (FT4), TSH, basal and ACTH-stimulated cortisol, testosterone, leutin izing hormone (LH), follicle-stimulating hormone (FSH), and prolactin were measured by radioimmunossay (RIA). Children with AN exhibited hig her basal and glucagon-stimulated C-peptide concentrations than the no nacanthotic obese group. Two hours after the oral load of glucose (1.7 5 g/kg), serum glucose concentration (6.3 +/- 1.4 mmol/L) was higher i n the acanthotic group versus the nonacanthotic group (5.2 +/- 0.8 mmo l/L). Impaired glucose tolerance was detected in two children with AN (10%), and in none of the nonacanthotic controls. Hypothyroidism was d iagnosed in two (10%) children with AN (TSH = 109 and 18 mIU/mL and FT 4 = 4.6 and 13.5 pmol/L respectively). while all the nonacanthotic chi ldren were euthyroid. Serum testosterone concentration was insignifica ntly lower in the acanthotic group (6.5 +/- 3.9 ng/dL) versus the nona canthotic children (8.3 +/- 4.5 ng/dL). Basal serum LH, FSH and prolac tin concentrations and basal and ACTH-stimulated cortisol levels did n ot differ between the two study groups. Plasma triglyceride concentrat ion was significantly higher in the acanthotic group (1.43 +/- 0.5 mmo l/L) versus the nonacanthotic group (1.05 +/- 0.45 mmol/L), and was co rrelated significantly with BMI (r = 0.466, P < 0.05). In conclusion, obesity is a significant risk factor for the development of AN in chil dren. AN is a reliable skin marker of hyperinsulinemia in obese childr en and adolescents, The prevalence of impaired glucose tolerance (10%) and primary hypothyroidism (10%) appears to be higher in obese acanth otic children than in those without AN.