Secukinumab Successfully Clears Rare Linear Psoriasis in Child With Loricrin Mutation: Case Report
A recent case report highlights how the biologic secukinumab successfully cleared a rare case of linear psoriasis. This clinical breakthrough uncovers a novel pathogenic link to a postzygotic loricrin mutation.
These findings are from the clinical report, published in the Indian Journal of Dermatology in January 2026 by Youcong Wang and colleagues of the Department of Dermatology, School of Medicine, Rui Jin Hospital, Shanghai Jiao Tong University in Shanghai, China.
Clinical Case Presentation
A 9-year-old girl with no significant family history of skin disease presented with a three-year history of a progressive, erythematous, scaly rash on her right upper limb that began without any apparent trigger. The skin lesions originated near her scapula and extended along Blaschko’s lines down to her hand, affecting her index nail. Histopathological analysis of a skin biopsy demonstrated hyperkeratosis, parakeratosis, epidermal acanthosis, and intraepidermal neutrophil infiltration, confirming isolated linear psoriasis. Prior treatments with topical corticosteroids and calcipotriol had failed to yield satisfactory results.
Following informed consent from her guardian, systemic biologic therapy with secukinumab was initiated. The patient received 150 mg subcutaneously weekly for the first month, followed by 150 mg every four weeks for maintenance. She exhibited rapid and significant clinical improvement, leaving only minimal residual erythematous plaques. After three months of therapy, due to the excellent clinical response, systemic treatment was discontinued at the patient's request, and she was maintained on topical moisturizers alone. The skin lesions remained stable and recurrence-free throughout a six-month post-treatment follow-up period.
Mechanistic Insights
To investigate the disease etiology, investigators performed comparative whole-exome sequencing on DNA extracted from peripheral blood and lesional scales collected via blade scraping. A somatic frameshift mutation in the loricrin gene (c.684dup: p.S229Vfs*107) was identified in the scale samples with a chimeric ratio of approximately 30.69%, but was absent in white blood cells. The finding was subsequently validated by Sanger sequencing. Immunofluorescence staining with an anti-loricrin antibody was negative in the patient's lesions, though strongly positive in both healthy and plaque psoriasis controls. This confirmed that the somatic mutation caused a loss of loricrin expression, disrupting the epidermal barrier and triggering interleukin-17A–mediated psoriasiform inflammation.
Implications for Clinicians
The case highlights the clinical utility of utilizing lesional scale scrapings rather than full-thickness skin biopsies to detect somatic mosaicism in epidermal disorders. Because somatic mutations are restricted to the epidermis, full-thickness biopsies dilute mutant DNA, whereas scale scraping offers a minimally invasive, high-yield diagnostic approach. Furthermore, combining interleukin-17A inhibitors with barrier-reinforcing emollient therapy represents a highly effective synergistic strategy for managing inflammatory dermatoses driven by primary epidermal barrier defects, paving the way for targeted clinical management.
Reference
Wang, Y., Zhang, L., Zheng, J., Li, X., & Chen, L. (2026). Linear psoriasis with postzygotic loricrin mutation successfully treated with secukinumab. Indian Journal of Dermatology, 2026.
