Acne keloidalis nuchae and thyroid diseases: a population‐based cohort study

Background The association between acne keloidalis nuchae (AKN) and thyroid diseases is yet to be investigated. Objective To evaluate the risk of developing hypothyroidism and hyperthyroidism among patients with AKN and to characterize the patients who have AKN and thyroid comorbidities. Methods A population‐based cohort study was conducted comparing AKN patients (n = 2,677) with age‐, gender‐, and ethnicity‐matched control subjects (n = 13,190) with regard to incident cases of hypothyroidism and hyperthyroidism. Adjusted hazard ratios (HRs) were estimated by Cox regression analysis. Results The incidence rates of hypothyroidism among patients with AKN and controls were estimated at 2.15 (95% CI, 1.49‐2.99) and 0.82 (95% CI, 0.66‐1.00) cases/1000 person‐years, respectively. The crude risk of developing incident hypothyroidism was 1.85‐fold greater in patients with AKN (HR, 1.85; 95% CI, 1.24‐2.78; P = 0.003). The elevated risk persisted following the adjustment for putative confounders (adjusted HR, 1.72; 95% CI, 1.03‐2.89; P = 0.040). The risk of hyperthyroidism was comparable in patients with AKN and controls both in the crude (HR, 1.55; 95% CI, 0.57‐4.22) and adjusted (adjusted HR, 1.92; 95% CI, 0.59‐6.21) analyses. Patients with coexistent AKN and thyroid diseases were significantly older at the onset of AKN, had more prominent female preponderance, and had a higher burden of comorbidity. Conclusions Patients with AKN are at an increased risk of hypothyroidism. Screening for hypothyroidism should be considered in AKN patients with a compatible clinical picture.