Subgroup analysis according to gestational age (< 50 vs. ≥ 51 days) showed that the GSTO1 levels were significantly higher in patients with EP whose gestational age ≥ 51 days compared to patients with IP whose gestational age ≥ 51 days (P = 0.01) and patients with EP whose gestational age < 50 days (P = 0.02). The gene discussed is GSTO1; the disease is incontinentia pigmenti.