BACKGROUND: The mean age of onset of hidradenitis suppurativa (HS) is between 20 and 24 years. Very few data about patients with early-onset HS exist. OBJECTIVE: To investigate the association of early-onset HS with the clinical characteristics: age, gender, body mass index (BMI), smoking, family history of HS, Hurley stage, and number of areas affected. METHODS: This was a retrospective study of the reported early age at HS onset (≤17 years old) with clinical characteristics and with the severity of HS at first consultation visit. RESULTS: In 166 patients, 42 patients (25.3%) reported early-onset HS. Compared to adult-onset HS, patients with early-onset HS were younger (mean age: 37 years vs. 27 years, P < 0.0001), had a significantly younger mean age of onset (28.2 years old vs. 14.5 years old, respectively, P < 0.0001), longer mean disease duration (8.8 years vs. 12.6 years, respectively, P = 0.011) and were less frequently smokers (P < 0.001), whereas there was no association with gender (P = 0.177) or BMI (0.086). Patients with a family history had increased risk for early-onset HS (OR: 2.45, 95% CI: 1.08-5.56). Early-onset HS was not associated with Hurley stage (OR: 1.12, 95% CI: 0.33-3.74) or with the number of body areas affected (OR: 1.54, 95% CI: 0.49-4.83). CONCLUSION: Early-onset HS was frequent and associated with a family history of HS. There was no difference in the severity of HS in adult life for patients with an onset of HS at ≤17 years, compared to patients with adult-onset, which may be reassuring information for these younger patients.