Secukinumab for Refractory Psoriasiform Cutaneous Manifestations in CTSC ‐Syndromic Epidermal Differentiation Disorder: A Pediatric Case Report

CTSC ‐syndromic epidermal differentiation disorder is a rare autosomal recessive genodermatosis caused by loss‐of‐function mutations in the cathepsin C gene. It is characterized by palmoplantar keratoderma and early‐onset periodontal destruction, and no standardized disease‐specific therapy has been established. We report a 3‐year‐old boy with disease onset in infancy, presenting with palmoplantar and generalized erythematous scaly lesions, severe pruritus, sleep disturbance, and nail roughness. Whole‐exome sequencing followed by Sanger sequencing identified compound heterozygous variants in the cathepsin C gene: c.774C>G inherited from his father and c.328G>T inherited from his mother. Treatment with cyclosporine combined with systemic retinoids failed to prevent disease progression. After pretreatment evaluation and written informed consent from his guardian, secukinumab was administered subcutaneously at a dose of 75 mg at weeks 0, 1, 2, 3, and 4, followed by once every 4 weeks thereafter. After 12 weeks of treatment, the patient showed marked improvement in clinical manifestations, quality‐of‐life scores, and disease severity scores, with no infectious complications during treatment at our institution. After secukinumab was continued locally, an infection involving the right foot and ankle led to treatment discontinuation, and a pulmonary infection was reported during later follow‐up.