Epitope-spreading phenomena in dipeptidyl peptidase-4 inhibitor-associated bullous pemphigoid

From Molecular Insights to Clinical Perspectives in Drug-Associated Bullous Pemphigoid

Bullous pemphigoid (BP), the most common autoimmune blistering disease, is characterized by the presence of autoantibodies targeting BP180 and BP230 in the basement membrane zone. This leads to the activation of complement-dependent and independent pathways, resulting in proteolytic cleavage at the dermoepidermal junction and an eosinophilic inflammatory response. While numerous drugs have been associated with BP in the literature, causality and pathogenic mechanisms remain elusive in most cases. Dipeptidyl peptidase 4 inhibitors (DPP4i), in particular, are the most frequently reported drugs related to BP and, therefore, have been extensively investigated. They can potentially trigger BP through the impaired proteolytic degradation of BP180, combined with immune dysregulation. DPP4i-associated BP can be categorized into true drug-induced BP and drug-triggered BP, with the latter resembling classic BP. Antineoplastic immunotherapy is increasingly associated with BP, with both B and T cells involved. Other drugs, including biologics, diuretics and cardiovascular and neuropsychiatric agents, present weaker evidence and poorly understood pathogenic mechanisms. Further research is needed due to the growing incidence of BP and the increasing identification of new potential triggers.

Bullous pemphigoid in diabetic patients treated by gliptins: the other side of the coin

Bullous pemphigoid (BP) is the most common autoimmune bullous skin disease that affects primarily patients older than 60 years. The majority of BP cases are spontaneous, but BP can also be triggered by certain drugs’ exposures. Since 2011, a growing number of observations has been reporting cases of BP in Type 2 diabetic patients. These forms have been linked to the use of a new category of anti-diabetic drugs called dipeptidyl peptidase inhibitors (DPP-4i) or gliptins, but to date, the exact pathophysiological mechanisms underlying this association are not completely elucidated. Although conventional and gliptin-associated BP are thought to share similar clinical and histopathological features, our thorough review of the most recent literature, shows that these 2 forms are quite distinct: DPP-4-i-associated BP seems to appear at an earlier age than spontaneous BP, it may manifest either as a noninflammatory or inflammatory phenotype, while the conventional form presents with a typical inflammatory phenotype. Additionally, an important distinctive histological feature was recently shown in Gliptin-associated BP: these forms may present a less significant eosinophils infiltrate in the upper dermis of peri-blister lesions compared to the skin of patients with spontaneous BP, and this seems a specific feature of the clinically non-inflammatory forms. In accordance with previous literature, we found that the direct immunofluorescence (DIF) gives identical findings in both DPP-4i-associated and conventional forms of BP which is an IgG and complement C3 deposition as a linear band at the dermal–epidermal junction in perilesional skin. Indirect immunofluorescence shows the presence of IgG circulating autoantibodies in the patient's serum which titer does not differ between spontaneous and DPP-4i-associated BP, while the specificity of these autoantibodies, may be different in spontaneous, induced non-inflammatory and induced inflammatory forms, epitope spreading phenomenon seems to play a role in determining these specificities. Further research, based on integrated epidemiological, clinical, histo-immunological and pharmacogenomic approaches, may give more insight into these forms of BP. This combined approach will allow to better define BP endotypes and to unveil the mechanism of spontaneous or drug-induced breakage of the immunotolerance to skin self-antigens.

Defining dipeptidyl peptidase-4 inhibitors-related bullous pemphigoid: A single-centre retrospective study

BACKGROUND

Many studies have corroborated the association of dipeptidyl peptidase-4 inhibitors (DPP4i) use with bullous pemphigoid (BP). It has been speculated that this drug-induced variant presents with a different clinical spectrum than conventional BP.

OBJECTIVE

To determine the prevalence of DPP4i-induced cases of BP and to evaluate whether gliptin-related BP has specific clinicopathological and immunological features.

METHODS

We conducted a retrospective, observational study of BP cases attended at our centre between January 2000 and June 2020. Epidemiological, clinical, histopathological and laboratory data were collected.

RESULTS

A total of 257 cases of BP were collected; 51 (24.3%) were on treatment with DPP4i. When analysing DPP4i-induced BP cases, generalized BP was the predominant pattern and scalp/mucosal involvement was found in 13 patients. Gliptin-related BP cases were associated to a decrease in the eosinophilic infiltrate (p = 0.000) and both the detection rate and concentration of anti-BP180 IgG were lower (p = 0.004, p = 0.001, respectively) than non-DPP4i cases.

LIMITATIONS

Retrospective, single-centre study.

CONCLUSION

Our large DPP4i-induced BP case series has highlighted that DPP4i-induced BP is characterized by generalized lesions and scalp involvement. Lower titres of anti-BP180 antibodies and a decrease in eosinophils infiltrating into the skin may be distinct features of DPP4i-related BP.

Clinical, Laboratory and Histological Features of Dipeptidyl Peptidase-4 Inhibitor Related Noninflammatory Bullous Pemphigoid

Bullous pemphigoid (BP) is an autoimmune blistering disease of elderly patients that has shown increasing incidence in the last decades. Higher prevalence of BP may be due to more frequent use of provoking agents, such as antidiabetic dipeptidyl peptidase-4 inhibitor (DPP4i) drugs. Our aim was to assess DPP4i-induced bullous pemphigoid among our BP patients and characterize the clinical, laboratory and histological features of this drug-induced disease form. In our patient cohort, out of 127 BP patients (79 females (62.2%), 48 males (37.7%)), 14 (9 females and 5 males) were treated with DPP4i at the time of BP diagnosis. The Bullous Pemphigoid Disease Area Index (BPDAI) urticaria/erythema score was significantly lower, and the BPDAI damage score was significantly higher in DPP4i-BP patients compared to the nonDPP4i group. Both the mean absolute eosinophil number and the mean periblister eosinophil number was significantly lower in DPP4i-BP patients than in nonDPP4i cases (317.7 ± 0.204 vs. 894.0 ± 1.171 cells/μL, p < 0.0001; 6.75 ± 1.72 vs. 19.09 ± 3.1, p = 0.0012, respectively). Our results provide further evidence that DPP4i-associated BP differs significantly from classical BP, and presents with less distributed skin symptoms, mild erythema, normal or slightly elevated peripheral eosinophil count, and lower titers of BP180 autoantibodies. To our knowledge, this is the first case series of DPP4i-related BP with a non-inflammatory phenotype in European patients.

The role of Dipeptidyl Peptidase-4 in cutaneous disease

Dipeptidyl peptidase-4 (DPP4) is a multifunctional, transmembrane glycoprotein present on the cell surface of various tissues. It is present in multiple molecular forms including cell surface and soluble. The role of DPP4 and its inhibition in cutaneous dermatoses have been a recent point of investigation. DPP4 exerts a notable influence on T-cell biology, the induction of skin-specific lymphocytes, and the homeostasis between regulatory and effector T cells. Moreover, DPP4 interacts with a broad range of molecules, including adenosine deaminase, caveolin-1, CXCR4 receptor, M6P/insulin-like growth factor II-receptor and fibroblast activation protein-α, triggering downstream effects that modulate the immune response, cell adhesion and chemokine activity. DPP4 expression on melanocytes, keratinocytes and fibroblasts further alters cell function and, thus, has crucial implications in cutaneous pathology. As a result, DPP4 plays a significant role in bullous pemphigoid, T helper type 1-like reactions, cutaneous lymphoma, melanoma, wound healing and fibrotic disorders. This review illustrates the multifactorial role of DPP4 expression, regulation, and inhibition in cutaneous diseases.

Bullous pemphigoid associated with dipeptidyl peptidase-4 inhibitors. A case series and analysis of cases reported in the Spanish pharmacovigilance database

BACKGROUND

Bullous pemphigoid (BP) has been associated with dipeptidyl peptidase-4 inhibitors (DPP4i). Clinical features, outcomes, and risk of BP for new DPP4i (linagliptin, saxagliptin, and alopgliptin) are not well established. Comparison of risk of BP appearance for DPP4i and other oral antidiabetic drugs (OADs) such as sodium glucose cotransporter 2 inhibitors has not been studied to date.

OBJECTIVES

To describe the prevalence, sociodemographic, clinical, and histopathological characteristics, and outcome after drug withdrawal in DPP-4i-associated BP cases from our hospital. To review all Spanish spontaneous notifications of BP where DPP4i or OADs were included as suspected drugs and calculate the reporting odds ratios (RORs).

METHODS

A retrospective observational study was performed examining the association between DDP4i and BP. Clinical features and RORs were analyzed. Data from the Spanish Pharmacovigilance System (SEFV) are included.

RESULTS

In our center, 28 of 89 patients with BP (31.5%) were under DPP4i treatment; 53.6% were male, and mean age was 80.8 years. BP debuted the first year after DPP4i in 57.2%. BP control was achieved within 3.7 months after drug withdrawal. Regarding SEFV, 22 of 972 spontaneous notifications were related to BP and DPP4i. RORs were superior for DPP4i compared to other OADs. Vildagliptin had the highest ROR.

CONCLUSIONS

We present the largest DPP4i-induced BP case series in a single center, with a detailed study of the sociodemographic, clinical, and histopathological characteristics of each patient, and their treatment and outcome. Vildagliptin had the highest risk. DPP4i-associated BP does not seem to have specific clinical characteristics.

Dipeptidyl Peptidase-4 Inhibitor-Associated Bullous Pemphigoid

Bullous pemphigoid (BP) is an organ-specific autoantibody-mediated blistering skin disease that mainly affects the elderly. Typical clinical features include the widespread blisters, often preceded by and/or associated with itchy urticarial or eczema-like lesions. BP patients have circulating autoantibodies against BP180 and/or the plakin family protein BP230 both of which are components of hemidesmosomes in basal keratinocytes. Most BP autoantibodies particularly target the epitopes within the non-collagenous NC16A domain of BP180. Clinical findings and murine models of BP have provided evidence of a pathogenic role of anti-NC16A autoantibodies. However, it is largely unknown what triggers the breakage of immunotolerance against BP180 in elderly individuals. The incidence of BP has been increased over the past two decades in several countries. Aside from aging populations, the factors behind this phenomenon are still not fully understood. Neurodegenerative diseases such as multiple sclerosis, Parkinson's disease, and certain dementias are independent risk factors for BP. Recently several case reports have described BP in patients with diabetes mellitus (DM) patients who have been treated with dipeptidyl peptidase-4 inhibitors (DPP-4i or gliptins), which are a widely used class of anti-DM drugs. The association between the use of DPP-4is, particularly vildagliptin, and BP risk has been confirmed by several epidemiological studies. Evidence suggests that cases of gliptin-associated BP in Japan display certain features that set them apart from cases of “regular” BP. These include a “non-inflammatory” phenotype, targeting by antibodies of different immunodominant BP180 epitopes, and a specific association with the human leukocyte antigen (HLA) types. However, recent studies in European populations have found no major differences between the clinical and immunological characteristics of gliptin-associated BP and “regular” BP. The DPP-4 protein (also known as CD26) is ubiquitously expressed and has multiple functions in various cell types. The different effects of the inhibition of DPP-4/CD26 activity include, for example, tissue modeling and regulation of inflammatory cells such as T lymphocytes. Although the pathomechanism of gliptin-associated BP is currently largely unknown, investigation of the unique effect of gliptins in the induction of BP may provide a novel route to better understanding of how immunotolerance against BP180 breaks down in BP.