Our study represents a significant advancement in the genetic characterization of HAE-nC1-INH, particularly in underrepresented populations. The identification of four novel MYOF variants provides the first evidence that MYOF-associated vascular permeability dysfunction may play a distinct role in HAE pathogenesis. While previous reports have suggested that MYOF variants may contribute to endothelial dysfunction, our findings establish a direct clinical correlation with persistent swelling, late-onset disease, and allergic comorbidities, further expanding the genetic heterogeneity of HAE-nC1-INH [10]. These findings suggest that disease mechanisms may extend beyond the bradykinin pathway to involve VEGF-mediated endothelial regulation, which has not been widely recognized in HAE pathophysiology [11].

Importantly, our study is the first to systematically analyze MYOF variants in an Asian cohort, revealing a higher frequency of MYOF variants compared to previous European reports [10]. This suggests potential ethnic and population-specific genetic predispositions, warranting further investigation into genetic-environmental interactions in HAE pathogenesis. Expanding genetic screening efforts across different populations will be essential to defining the true genetic landscape of HAE-nC1-INH and determining whether specific variants contribute to distinct phenotypic variations observed across geographic regions [12]. Given the growing evidence that MYOF plays a role in vascular permeability, further studies using functional validation approaches will be necessary to understand the pathogenic mechanisms of these variants and their implications for targeted therapies.

The discovery of HS3ST6 variants in HAE-nC1-INH further highlights alternative mechanisms of vascular permeability dysregulation, reinforcing the complex genetic architecture of this condition. HS3ST6, involved in heparan sulfate biosynthesis, has been linked to vascular integrity and inflammatory signaling, suggesting that mutations in this gene may promote non-bradykinin-dependent pathways of angioedema [7]. Our study found that patients with HS3ST6 variants displayed persistent swelling resistant to icatibant, reinforcing the need for further research into alternative therapeutic targets in HAE-nC1-INH cases that do not fully respond to traditional bradykinin-targeted therapies.

Our real-world evaluation of lanadelumab in a genetically diverse HAE cohort provides compelling evidence for the importance of personalized treatment approaches in HAE-nC1-INH. While lanadelumab effectively reduced attack frequency in most patients, its efficacy varied significantly across different genetic backgrounds, particularly in carriers of MYOF, KNG1, and HS3ST6 mutations. This variability in response underscores the necessity of tailoring HAE treatment strategies based on individual genetic profiles, as kallikrein inhibition alone may not be universally effective across all HAE-nC1-INH subtypes. Patients with HAE-FXII, one of the more extensively studied forms of HAE-nC1-INH, often exhibit bradykinin-mediated angioedema, and account for approximately 30% of cases in European cohorts [4]. The most frequently reported FXII mutations include c.983 C > A (p.Thr328Lys) and c.983 C > G (p.Thr328Arg) [21], a large deletion mutation spanning 72 base pairs (c.971_1018 + 24del72) [22], and a duplication mutation (c.892_909dup) [23]. HAE-FXII predominantly affects women, with attacks often triggered by estrogen fluctuations, and typically involves the skin, gastrointestinal tract, and occasionally the upper airway.

However, our HAE-FXII case presented with a distinct clinical phenotype, diverging from the classical hormonally influenced exacerbations commonly described in the literature. Unlike previous reports, our patient exhibited persistent, non-cyclical swelling, with no clear exacerbations linked to menstruation, pregnancy, or oral contraceptive use. Furthermore, despite initial resistance to therapy, her symptoms resolved abruptly following multiple lanadelumab administrations, suggesting a possible delayed therapeutic response in certain HAE-FXII carriers. This atypical disease progression and treatment response raises important questions regarding pathophysiological heterogeneity within FXII mutation carriers and suggest that additional molecular mechanisms beyond bradykinin dysregulation may contribute to persistent angioedema. Further research is warranted to elucidate whether FXII-driven HAE subtypes may involve alternative pathways or additional genetic modifiers influencing disease severity and treatment outcomes.

Another notable observation in our study was the patient harboring an HS3ST6 variant, who exhibited persistent edema resistant to conventional therapies. This clinical presentation contrasts with previous reports of HS3ST6-associated HAE, particularly the case of a c.430 A > T (p.Thr144Ser) mutation, where affected individuals displayed episodic swelling primarily involving the skin, throat, and gastrointestinal mucosa [6]. Our patient, however, presented with chronic, non-resolving edema rather than the acute, recurrent attacks typically seen in HAE, raising the possibility that different HS3ST6 variants may contribute to distinct angioedema phenotypes.

The biological function of HS3ST6 in heparan sulfate biosynthesis has been well-documented, with established roles in regulating endothelial function and inflammatory responses [7]. Disruption of heparan sulfate biosynthesis could impair the normal endocytosis of kininogen, leading to increased bradykinin production and subsequent excessive vascular permeability. However, the failure of icatibant to alleviate symptoms in our HS3ST6 patient, despite its well-established efficacy in bradykinin-mediated angioedema, suggests that this variant may also contribute to non-bradykinin-driven angioedema pathways. We hypothesize that HS3ST6 variants could alter endothelial barrier function via mechanisms beyond direct kallikrein-kinin system activation, warranting further functional studies to confirm its role and identify potential therapeutic targets.

MYOF mutations are an uncommon but emerging genetic cause of HAE, with a limited number of cases documented in the literature. One previous study described three affected female relatives in an Italian family harboring a c.651G > T (p.Arg217Ser) mutation, with episodic swelling of the face, lips, and oral mucosa [24]. However, our study significantly expands upon prior findings by identifying four distinct MYOF variants across multiple unrelated patients, including both male and female carriers, each displaying heterogeneous clinical phenotypes. This genetic and clinical diversity suggests that MYOF variants may not represent a single disease entity but rather a broader category of vascular permeability disorders with variable expressions.

Although HAE is traditionally classified as a bradykinin-mediated disorder, the presence of MYOF variants in our cohort suggests that other regulatory pathways, such as VEGF signaling, may also play a role in disease pathophysiology [10]. MYOF (myoferlin) is a critical regulator of VEGFR2, and its dysfunction could lead to excessive vascular permeability and abnormal endothelial barrier function. The co-occurrence of pruritic rashes and angioedema in certain MYOF carriers further suggests that histamine and other inflammatory mediators may also contribute to edema formation, distinguishing MYOF-associated HAE from classical bradykinin-mediated angioedema. The potential involvement of multiple mediators underscores the need for further in vitro and in vivo studies to determine whether MYOF-driven HAE could benefit from alternative therapeutic approaches beyond bradykinin-targeted treatments.

MYOF mutation-associated HAE has rarely been reported worldwide, making our cohort particularly valuable in understanding the genetic and clinical diversity of this HAE subtype. Among our patients with MYOF variants, one individual also harbored a SERPING1 variant and was diagnosed with HAE-2, demonstrating that MYOF mutations may coexist with other pathogenic variants and contribute to complex disease presentations. Interestingly, we observed a notably high prevalence of MYOF variants in our Chinese cohort, raising questions about whether genetic predisposition, environmental factors, or population-specific variations contribute to this increased frequency.

In addition to its potential role in bradykinin-independent vascular permeability regulation, MYOF mutations may also lower the threshold for endothelial dysfunction, leading to exaggerated edema responses even under normal concentrations of vasoactive substances. The partial but incomplete response to lanadelumab in one of our HAE-MYOF patients suggests that MYOF-associated angioedema may not be fully dependent on kallikrein activation and may require alternative treatment strategies targeting VEGF or endothelial barrier function. Although lanadelumab significantly reduced attack frequency, our findings emphasize the importance of considering genetic background when selecting long-term prophylactic therapies. Future research should explore whether combining kallikrein inhibitors with VEGF-targeted agents could provide a more effective therapeutic approach for MYOF-driven HAE.

Diagnosing HAE-nC1-INH remains challenging, as current diagnostic approaches rely heavily on clinical manifestations, including recurrent, unexplained angioedema episodes affecting the skin, airway, and gastrointestinal tract, in the setting of normal C1-INH levels and function. However, HAE-nC1-INH is a genetically and phenotypically heterogeneous disorder, and reliance on phenotypic assessment alone often leads to diagnostic uncertainty and delays in appropriate treatment [25]. In our study, we observed substantial clinical heterogeneity among patients, including unusual presentations such as persistent swelling in HAE-FXII, MYOF, and HS3ST6 variant carriers, further underscoring the limitations of a purely phenotype-driven approach. In these cases, standard biochemical testing was insufficient to establish a definitive diagnosis, highlighting the need for integrating genetic testing into clinical workflows.

Genetic testing, while valuable, does not always provide clear-cut answers, as the relationship between genotype and phenotype in HAE-nC1-INH is complex and not fully understood. Different mutations within the same gene can lead to highly variable clinical presentations, complicating efforts to establish definitive diagnostic criteria. Some patients with known pathogenic variants remain asymptomatic, while others experience severe, refractory disease, indicating that additional genetic, epigenetic, or environmental factors may contribute to disease expression. Given this variability, our findings support the integration of genetic testing into existing diagnostic algorithms, not as a standalone tool, but as a complementary approach alongside clinical and laboratory assessments to refine the classification of HAE-nC1-INH and improve individualized patient management. We hope that our insights will contribute to updates in international diagnostic guidelines, ensuring that genetic findings are appropriately incorporated into standardized HAE evaluation protocols.

Since 2021, lanadelumab—a monoclonal antibody targeting plasma kallikrein—has been available in mainland China for the long-term prophylaxis of HAE. This availability provided us with a unique opportunity to evaluate its real-world efficacy among patients with genetically diverse forms of HAE, including HAE-1, HAE-2, and HAE-nC1-INH. To our knowledge, this is the first study to systematically assess lanadelumab’s performance in Eastern Asian HAE patients, with particular attention to its efficacy across different genetic backgrounds.

Among our HAE-1 and HAE-2 patients, all seven individuals achieved complete remission of edema episodes during biweekly lanadelumab therapy, supporting its high efficacy in conventional bradykinin-mediated HAE. However, its effects in HAE-nC1-INH were more variable, reinforcing the notion that some genetic subtypes may not be entirely driven by kallikrein overactivation. One patient with an HAE-FXII variant experienced an atypical response, requiring ten consecutive injections before achieving complete symptom resolution, suggesting that certain genetic backgrounds may influence the timeline and effectiveness of treatment.

Recognizing the high cost and limited accessibility of lanadelumab in China, we also explored the possibility of extending dosing intervals. After six months of stable disease control, one patient successfully extended the dosing interval to 16 weeks, while others maintained remission with a less-than-four-week interval. Although preliminary and limited by sample size, these findings suggest that personalized dose-interval adjustments may help optimize treatment efficiency while reducing financial burden, particularly in regions where high-cost biologics remain a significant barrier to care. Future larger-scale studies are warranted to determine whether individualized dosing schedules can maintain efficacy without compromising disease control, and whether biomarkers such as residual C1-INH activity or attack frequency could guide patient-specific treatment protocols.

The patient with the FXII gene variant in our cohort presented an intriguing clinical scenario, as her symptoms persisted for nearly five months despite ongoing lanadelumab therapy. Initially, she showed minimal improvement, but after ten consecutive injections, she achieved complete remission, with no further attacks reported over the next 12 months. This delayed but eventual full response suggests that certain HAE-FXII cases may require prolonged kallikrein inhibition before reaching maximum therapeutic benefit.

The variable responsiveness of HAE-FXII to lanadelumab reflects the complexity of HAE-nC1-INH and raises several critical questions regarding treatment mechanisms and patient selection. While kallikrein inhibition is highly effective for bradykinin-mediated angioedema, it is possible that other pathways—such as alternative contact system activation or endothelial barrier dysfunction—contribute to symptom persistence in certain genetic backgrounds. Although several reports have confirmed lanadelumab’s efficacy in HAE-FXII [14], treatment options for other HAE-nC1-INH subtypes remain limited, particularly for HS3ST6 and MYOF-driven disease. Our findings highlight the urgent need for further research into the molecular underpinnings of HAE-nC1-INH, as well as the development of precision medicine approaches tailored to specific genetic drivers.

Our study also provides an updated epidemiologic assessment of HAE in China, offering new insights into the distribution of HAE subtypes in Eastern Asian populations. In Western cohorts, HAE-2 accounts for approximately 15% of all HAE cases [26]. However, in our study of 27 Chinese HAE patients, only two were diagnosed with HAE-2, suggesting a notably lower prevalence compared to Western populations. These findings align with two prior large-scale Chinese studies, which reported HAE-2 prevalences of 2.26% (3/133) 26 and 1.27% (2/158) [27], respectively. Such discrepancies in subtype distribution across populations emphasize the importance of local epidemiologic surveillance, as regional genetic backgrounds, environmental influences, and referral biases may contribute to these variations.

Further supporting this geographic variability, data from South Korea indicate that 9.2% (6/65) of HAE patients have HAE-2 [28], while Danish reports suggest a prevalence of approximately 6.1% (5/82) [29]. These comparative analyses reinforce the need for country-specific epidemiological studies to ensure that HAE diagnostic and treatment guidelines are appropriately adapted to regional patient populations. The lower observed prevalence of HAE-2 in China raises the possibility that genetic variations unique to East Asian populations may influence disease susceptibility and subtype distribution, warranting further genomic studies to identify potential population-specific risk factors.

In addition to subtype distribution, our findings highlight important differences in disease onset and progression between Eastern and Western HAE cohorts. The mean age at first symptom onset in our Chinese cohort was approximately 26 years, which closely mirrors prior Chinese, Taiwanese, and South Korean reports. However, European and North American studies frequently report earlier disease onset, often in childhood or adolescence [26, 27, 29]. Earlier onset has been associated with more severe disease progression, potentially explaining why HAE appears to have a lower incidence and seemingly milder presentation in East Asian populations. These ethnic and regional differences further emphasize the importance of genetic and environmental modifiers in shaping disease expression, reinforcing the need for population-specific studies to refine clinical management strategies.

Despite advances in diagnostic awareness, diagnostic delay remains a critical challenge. Historical reports from mainland China indicate average delays of 13–16 years [26,27,28,29], whereas our study observed an average diagnostic delay of 8 years. While this suggests gradual improvement in early recognition, nearly a decade-long delay in diagnosis remains far from optimal for a potentially life-threatening condition. Enhanced education for healthcare professionals, increased availability of genetic and biochemical testing, and the development of standardized diagnostic workflows are urgently needed to further shorten diagnostic delays and ensure timely intervention for HAE patients.

Abdominal involvement is a common and often debilitating feature of HAE, frequently leading to severe pain that can mimic surgical emergencies, sometimes resulting in unnecessary medical procedures such as exploratory laparotomies or appendectomies [1, 12, 18]. In our cohort, 14 of 27 patients (51.85%) experienced abdominal attacks, underscoring the importance of recognizing gastrointestinal manifestations as part of the HAE disease spectrum. Notably, three patients with HAE-nC1-INH and MYOF variants presented with particularly severe abdominal symptoms, raising important questions about potential genotype-phenotype correlations in gastrointestinal involvement.

While it remains uncertain whether MYOF mutations have a direct mechanistic role in triggering abdominal symptoms, there is a growing body of evidence suggesting that MYOF dysfunction may contribute to increased vascular permeability, not only in cutaneous tissues but also in the intestinal vasculature [10]. MYOF is known to interact with VEGFR2 signaling, which regulates endothelial barrier integrity, and its dysfunction could increase susceptibility to intestinal edema and bowel wall thickening, similar to what is observed in bradykinin-driven abdominal HAE attacks. Awareness that certain genetic variants, particularly MYOF mutations, may predispose patients to gastrointestinal involvement could aid in earlier recognition and more targeted treatment strategies for these cases. Future studies investigating the role of MYOF in intestinal permeability could provide valuable insights into alternative disease pathways and potential therapeutic targets beyond kallikrein inhibition.

The association between HAE and autoimmune diseases has been well documented, with estimates suggesting that 11–12% of HAE patients also have concurrent autoimmune conditions, most commonly systemic lupus erythematosus (SLE) [30,31,32,33,34,35]. Our findings are consistent with this epidemiologic trend, as 7 of our 27 patients (26%) had coexisting autoimmune disorders, including both HAE-1 and HAE-nC1-INH cases. Although we did not identify a clear relationship between autoimmune disease activity and the frequency or severity of HAE attacks, it is possible that dysregulation of the complement system, heightened B-cell activity, or inflammatory mediators contribute to both conditions simultaneously [31, 32].

The pathophysiology linking HAE to autoimmunity remains poorly understood, but previous studies suggest that defective complement regulation, abnormal cytokine profiles, and chronic immune activation may be shared mechanisms between HAE and certain autoimmune conditions [34, 35]. Interestingly, a recent case report described a patient with multiple sclerosis (MS) who experienced significant improvement in HAE symptoms following MS-directed immunotherapy, suggesting that modulating immune dysregulation may influence angioedema severity and frequency. These observations highlight the need for further research into the immunological mechanisms underlying HAE, particularly in patients with coexisting autoimmune conditions, as such insights could facilitate the development of novel therapies targeting both immune dysregulation and vascular permeability [35, 36].

Another noteworthy finding in our study was that 11 out of 27 HAE patients (40.74%) also had allergic diseases, and 4 patients experienced angioedema episodes accompanied by pruritic rashes, which is uncommon in traditionally bradykinin-mediated HAE. This raises important questions about the role of mast cells, histamine release, and allergic pathways in specific HAE subtypes, particularly in HAE-nC1-INH. Among these cases, a patient with a MYOF variant reported significant improvement in symptoms following the avoidance of specific food allergens, which were identified through IgG4 testing.

Furthermore, an off-study case involving a patient with low C1-INH function and recurrent angioedema demonstrated a marked reduction in attack frequency and severity following treatment with omalizumab, an anti-IgE monoclonal antibody. These findings suggest that certain HAE subtypes—especially those with MYOF mutations—may involve additional inflammatory or mast cell-mediated pathways, rather than being exclusively bradykinin-driven [10]. While more rigorous investigation is needed, these preliminary observations point toward a possible overlap between HAE and allergic pathophysiology, expanding the potential therapeutic landscape to include anti-IgE therapies or allergen avoidance strategies in select cases. This new perspective on HAE pathogenesis could provide clinicians with additional treatment options, particularly for patients who exhibit partial responsiveness to bradykinin-targeted therapies.

This study contributes significantly to the understanding of HAE in an Asian context, particularly given the rarity and under-recognition of HAE-nC1-INH worldwide. As the first study to characterize both the genetic landscape and real-world treatment outcomes of HAE-nC1-INH in an Asian population, our findings highlight both the genetic diversity and therapeutic potential within this patient group. The identification of novel MYOF, KNG1, and HS3ST6 variants, along with the differential responses to lanadelumab, underscores the heterogeneity of HAE-nC1-INH and the necessity for a more individualized approach to diagnosis and treatment.

The classification of certain HAE-nC1-INH cases with persistent edema highlights a clinically relevant, genetically defined phenotype that diverges from classical recurrence-based definitions but remains consistent with the known pathophysiology and treatment profile of bradykinin-mediated angioedema. Recognizing this spectrum is essential for improving diagnosis and guiding appropriate therapeutic strategies, especially in populations with rare or novel variants.

Despite the significant contributions of this study, we acknowledge several limitations. The low incidence of HAE, combined with the limited sample size and single-center design, constrains the generalizability of our findings. Additionally, longitudinal follow-up is needed to further assess long-term treatment outcomes, particularly with adjusted lanadelumab dosing intervals. Nonetheless, these initial observations serve as a foundation for future multicenter collaborations, which will be critical for accurately delineating epidemiology, genotype-phenotype relationships, and treatment responses in diverse HAE populations.

Ultimately, advancing these research efforts will improve diagnostic precision, enhance therapeutic decision-making, and contribute to the development of more personalized management strategies. These efforts will not only optimize patient care within Asia but also provide broader insights into HAE pathogenesis worldwide, reinforcing the need for standardized diagnostic and treatment protocols tailored to regional and genetic variations. By leveraging multinational collaborations and cutting-edge genomic analysis, the field can move toward precision medicine approaches, ultimately enhancing patient outcomes and improving quality of life for individuals living with HAE.