Case Report: Certolizumab pegol as a potential rescue option for severe erythema multiforme associated with pustular psoriasis during pregnancy

BackgroundSevere erythema multiforme (EM) and pustular psoriasis presenting during pregnancy (PPP) are rare inflammatory dermatoses that may adversely affect maternal and fetal outcomes. Their coexistence during pregnancy is exceptionally uncommon, and therapeutic decisions are challenging because of limited evidence and concerns regarding fetal safety.Case presentationA 37-year-old woman at 30 weeks of gestation presented with rapidly progressive targetoid erythema, papulovesicular lesions, blisters, pustules, acral edema, and mild oral mucosal erosion. Severe EM was initially suspected based on the presence of targetoid lesions and mucosal involvement. During hospitalization, the development of sterile pustules and pustular plaques suggested concomitant PPP. Histopathological examination demonstrated interface dermatitis with focal epidermal necrosis in the arm lesion, consistent with EM, and intraepidermal pustule formation with neutrophilic infiltration in the abdominal lesion, supporting PPP. Potential EM triggers were investigated. HSV-I/II IgM was positive, whereas Mycoplasma pneumoniae testing was negative; however, no definitive infectious trigger was identified. Hydroxychloroquine, initiated approximately 2 weeks before disease onset by an external obstetrician, was discontinued because drug-associated EM was considered possible, although causality could not be confirmed. Despite treatment with intravenous methylprednisolone, intravenous immunoglobulin (IVIG), and corticosteroid pulse therapy, the disease continued to progress. Histopathological examination supported the diagnoses of EM and PPP. Genetic analysis revealed wild-type IL36RN and a heterozygous IL36G c.404T > C variant of uncertain significance.Intervention and outcomeAfter infection was excluded and informed consent was obtained, a single dose of certolizumab pegol 400 mg was administered subcutaneously during the early corticosteroid tapering phase following methylprednisolone pulse therapy Cutaneous lesions showed marked improvement within 72 h after certolizumab administration. Corticosteroids were successfully tapered. The patient delivered a healthy male infant vaginally at 39 weeks and 1 day of gestation. No maternal or neonatal adverse events were observed, and remission was maintained during one year of postpartum follow-up.ConclusionThis case highlights the diagnostic complexity and therapeutic challenges of concurrent severe EM and PPP during pregnancy. Although the contribution of previous corticosteroid and IVIG therapy cannot be completely excluded, the temporal association between certolizumab pegol administration and clinical improvement suggests that TNF-α blockade may represent a potential option. Further clinical experience and registry-based studies are required to clarify its efficacy and optimal clinical application.