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Chronic Spontaneous Urticaria with Biochemical C1 Inhibitor Deficiency: A Case Report of Suspected Overlap with Hereditary Angioedema

Chen F, Yang F, Li X, Li T

Clinical, cosmetic and investigational dermatology, 2026

Abstract

Rationale: Chronic spontaneous urticaria (CSU) and hereditary angioedema caused by C1 inhibitor (C1-INH) deficiency are mechanistically distinct disorders. When persistent wheals coexist with recurrent throat or abdominal symptoms, however, assigning individual episodes to mast-cell- or bradykinin-mediated pathways can be difficult.

Patient concerns: A 36-year-old Chinese woman developed recurrent wheals and pruritus in 2020. Beginning in 2024, she also reported episodic throat tightness and intermittent abdominal pain despite high-dose H1 antihistamines, systemic corticosteroids, and omalizumab.

Diagnoses: Repeated complement testing in 2025 showed low C4, reduced C1-INH concentration, and impaired C1-INH function. Her mother had similar biochemical abnormalities. These findings supported biochemical C1-INH deficiency in a patient with active CSU, but the mechanism of individual throat and abdominal episodes remained uncertain. Whole-exome sequencing, including exome-based copy-number analysis, identified no reportable pathogenic or likely pathogenic variant in the prioritized angioedema-related genes; however, not all currently recognized HAE-associated genes were included, and gene-level coverage metrics were unavailable.

Interventions: Documented treatment included H1 antihistamines, systemic corticosteroids, cyclosporine, and omalizumab. Subcutaneous icatibant and lanadelumab were also administered, but the retrospective records did not permit reliable assessment of…

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