Autoimmune blistering disorders (AIBD) are a diverse group of chronic disorders characterized by developing skin and mucosal blisters due to immune mediated destruction of epidermal and dermo-epidermal structures. Dermatitis Herpetiformis (DH) and Bullous Pemphigoid (BP) are of particular clinical significance due to their prevalence, morbidity, increased mortality, and association with systemic conditions. 

The thesis relies on Swedish National Patient Register (NPR) data which was established by the Swedish National Board of Health and Welfare in 1964. Since 1987, it has provided nearly complete coverage of all inpatient care in Sweden, including public and private sectors. 

This abstract illustrates findings from four recent studies conducted in Sweden. These studies sought to investigate various epidemiological aspects of DH and BP, including associated cancer, mortality rates, comorbidities and incidence trends, and the validity of DH diagnosis code in the NPR. 

Study I investigated the national incidence of DH in Sweden between 2005 and 2018. We also evaluated the validity of DH diagnoses recorded in the Swedish NPR using the International Classification of Diseases, 10th Revision (ICD-10) diagnostic code L13.0.The results show that DH's estimated mean annual incidence was 0.93 per 100,000 individuals (95% CI: 0.79–1.08). The condition exhibited an equal gender distribution, with a female-tomale ratio of 1:1, and the mean age at diagnosis was approximately 61 years. While the accuracy of DH diagnoses in the NPR was validated by reviewing medical records alongside histopathological and immunopathological findings, yielding a positive predictive value (PPV) of 62.5%. 

Study II, a nationwide cohort analysis of 5,739 BP patients and 17,168 matched controls, investigated the association of malignancy in patients with BP in Sweden from 2005 to 2016. Overall, the study found no evidence of an increased occurrence of cancer in patients with BP. Notably, men with BP had fewer cases of genital cancer in the year preceding diagnosis. In contrast, BP was associated with an increased occurrence of lymphoma and squamous cell carcinoma of the skin (cSCC). 

In study III, we had a similar setting as in study II; we retrospectively investigated the 1- and 10-year mortality and overall all-cause mortality in patients with BP in Sweden. All-cause mortality was significantly higher in the BP cohort, with 1-year mortality at 21.2% and 10- year mortality at 80.2%. Cardiovascular diseases (CVD) was the leading cause of death (25.3%). Notably, patients treated with combined methotrexate (MTX), prednisolone, and 4 potent topical steroids showed better survival outcomes compared to those receiving other treatments. 

In study IV, with a similar setting as in Studies II and III, we retrospectively studied the comorbidities associated with BP before and after BP diagnosis. Before BP diagnosis, patients had significantly higher odds of neurological and psychiatric disorders, including dementia, Parkinson’s disease, epilepsy, amyotrophic lateral sclerosis (ALS), multiple sclerosis (MS), schizophrenia, unipolar/bipolar disorders and suicide. Metabolic, CVD, autoimmune and dermatological diseases such as diabetes, stroke, systemic lupus erythematosus (SLE), systemic sclerosis, psoriasis, lichen planus, alopecia areata and vitiligo were also more common, especially in the year prior to diagnosis. After diagnosis, the overall hazard ratio (HR) for developing comorbidities was 2.88 (95% CI: 2.68–3.10) within the first year and remained elevated at 1.57 (95% CI: 1.44–1.71) thereafter. BP patients continued to experience higher rates of neurodegenerative, psychiatric, autoimmune, metabolic, CVD, and dermatological conditions, indicating a substantial and persistent comorbidity burden in this population. 

Collectively, these studies highlight critical gaps in epidemiological knowledge and emphasize the need for further research, particularly in Sweden, where data remains limited. Understanding the incidence, cancer occurrence, mortality rates, and comorbidities associated with these blistering disorders can reform healthcare strategies, improve patient outcomes, and guide future research efforts into these debilitating conditions.