Increased natural autoantibody activity to cytoskeleton proteins in sera from patients with necrobiosis lipoidica, with or without insulin-dependent diabetes mellitus

The Intersection of Dermatological Dilemmas and Endocrinological Complexities: Understanding Necrobiosis Lipoidica-A Comprehensive Review

BACKGROUND

Necrobiosis lipoidica (NL) is a rare granulomatous skin disorder with a predilection for females, often associated with diabetes mellitus (DM). This paper aims to comprehensively review the literature on NL, focusing on its association with DM, thyroid disorders, and the metabolic syndrome.

METHODS

A systematic search was conducted in English-language literature from inception to October 2023, utilizing PubMed. We identified 530 studies and selected 19 based on clinical significance, statistical support, and relevance to the paper's goals.

RESULTS

The coexistence of NL and DM is prevalent, with rates ranging from 11% to 65.71%. NL may precede DM diagnosis and a correlation between NL and increased daily insulin requirements has been observed in such patients. NL is suggested as a potential prognostic marker for DM complications; however, recent studies question this association, highlighting the need for further research. Studies in the context of NL and Thyroid Disease indicate a correlation, especially with autoimmune thyroiditis. Regarding NL and Metabolic Syndrome, the prevalence of metabolic syndrome among NL patients is notably higher than in the general population. Additionally, DM patients with ulcerated NL commonly exhibit hypertension or obesity, raising questions about the potential influence of hypertension and obesity on NL ulcerations.

CONCLUSION

Additional research is required to untangle the complex connections between NL and various comorbidities.

TLR7 and IgM: Dangerous Partners in Autoimmunity

The B cell antigen receptor (BCR)-repertoire is capable of recognizing a nearly unlimited number of antigens. Inevitably, the random nature of antibody gene segment rearrangement, needed in order to provide mature B cells, will generate autoreactive specificities. Once tolerance mechanisms fail to block the activation and differentiation of autoreactive B cells, harmful autoantibodies may get secreted establishing autoimmune diseases. Besides the hallmark of autoimmunity, namely IgG autoantibodies, IgM autoantibodies are also found in many autoimmune diseases. In addition to pathogenic functions of secreted IgM the IgM-BCR expressing B cell might be the initial check-point where, in conjunction with innate receptor signals, B cell mediated autoimmunity starts it fateful course. Recently, pentameric IgM autoantibodies have been shown to contribute significantly to the pathogenesis of various autoimmune diseases, such as rheumatoid arthritis (RA), autoimmune hemolytic anemia (AIHA), pemphigus or autoimmune neuropathy. Further, recent studies suggest differences in the recognition of autoantigen by IgG and IgM autoantibodies, or propose a central role of anti-ACE2-IgM autoantibodies in severe COVID-19. However, exact mechanisms still remain to be uncovered in detail. This article focuses on summarizing recent findings regarding the importance of autoreactive IgM in establishing autoimmune diseases.

Adaptive tolerance: Protection through self-recognition

The random nature of immunoglobulin gene segment rearrangement inevitably leads to the generation of self-reactive B cells. Avoidance of destructive autoimmune reactions is necessary in order to maintain physiological homeostasis. However, current central and peripheral tolerance concepts fail to explain the massive number of autoantibody-borne autoimmune diseases. Moreover, recent studies have shown that in physiological mouse models autoreactive B cells were neither clonally deleted nor kept in an anergic state, but were instead able to mount autoantibody responses. We propose that activation of autoreactive B cells is induced by polyvalent autoantigen complexes that can occur under physiological conditions. Repeated encounter of autoantigen complexes leads to the production of affinity-matured autoreactive IgM that protects its respective self-targets from degradation. We refer to this novel mechanism as adaptive tolerance. This article discusses the discovery of adaptive tolerance and the unexpected role of high affinity IgM autoantibodies.

Comorbidity and Therapeutic Approaches in Patients with Necrobiosis Lipoidica

BACKGROUND

Necrobiosis lipoidica (NL) is a rare granulomatous disorder of unknown aetiology. Randomized controlled studies are not available due to it being an orphan disease.

OBJECTIVES

We evaluated patients in 2 dermatological centres to cluster data about epidemiology, the therapeutic approaches for NL, and their efficacy.

MATERIALS AND METHODS

Comorbidity and the efficacy of the applied treatment was assessed for 98 patients.

RESULTS

We identified 54% of patients with concomitant diabetes and 19% with thyroidal disorders. Topical steroids (85.7%) were predominantly used followed by calcineurin inhibitors (31%) and phototherapy (41.8%). Systemically, fumaric acid esters were more frequently applied (26.8%) than steroids (24.4%) and dapsone (24.4%). Steroids, compression therapy, calcineurin inhibitors, phototherapy, fumaric acid esters, and dapsone showed remarkable efficacy.

CONCLUSION

Therapeutic options were chosen individually in accordance with the severity of NL and presence of ulceration. Topical calcineurin inhibitors, systemic application of fumaric acid esters, and dapsone represent effective alternatives to the use of steroids.

Anti-cardiac troponin antibodies in clinical human disease: a systematic review

Anti-cardiac troponin antibodies have been studied in different types of clinical diseases and in healthy populations. A systematic review of published data on anti-troponin antibodies was carried out (search performed on PubMed, ISI Web of Knowledge and Scopus databases). From title and abstract analysis, thirty-three articles were included that met the pre-specified criteria; after full-text analysis, nine articles were excluded. Most studies assessed anti-troponin I antibodies. The prevalence of anti-cardiac troponin antibodies in healthy individuals ranged from 0.0% to 20.0%. The prevalence of anti-troponin I autoantibodies in dilated cardiomyopathy (DCM) ranged from 7.0% to 22.2%. Other conditions under study were myocardial infarction, ischemic cardiomyopathy (ICM), peripartum cardiomyopathy (PPCM), Chagas disease, Emery-Dreifuss muscular dystrophy (EDMD) and renal transplantation. In the different patient populations studied, anti-cardiac troponin antibodies have been shown to be either positively or negatively associated with prognostic and clinical features. In what concerns a possible value as biomarkers, these assays have not emerged up to the present moment as important aids for practical clinical decisions in cardiac or other types of patients. In what concerns pathophysiology, anti-cardiac troponin autoantibodies may play a role in different diseases. It can be speculated that these antibodies could be involved in perpetuating some degree of cardiac injury after an event, such as myocardial infarction or PPCM.

Risk factors for necrobiosis lipoidica in Type 1 diabetes mellitus

AIMS

To compare the clinical and metabolic characteristics of patients with Type 1 diabetes and necrobiosis lipoidica with those of patients with Type 1 diabetes who do not have necrobiosis lipoidica. A multicentre analysis was performed.

METHODS

Clinical and laboratory data were obtained from 64 133 patients (aged 0-25 years) with Type 1 diabetes with and without necrobiosis lipoidica who were registered in the German/Austrian Diabetes Prospective Documentation Initiative registry. Data were analysed using multivariable regression modelling. Age, diabetes duration, treatment year and sex were considered as confounding factors.

RESULTS

Results adjusted for demographic variables are presented. In patients with necrobiosis lipoidica, metabolic control was worse (HbA_1c 72 vs. 67 mmol/mol, 8.7% vs. 8.3%; P = 0.0065) and the duration of diabetes was longer [6.24 (3.28-9.97) vs. 5.11 (2.08-8.83) years; P = 0.014; not adjusted]. Patients with necrobiosis lipoidica required higher insulin doses than those without (1.02 vs. 0.92 U/kg/day; P < 0.0001). There was no significant difference in the frequency of microvascular complications (microalbuminuria and retinopathy) between the groups. Furthermore, 24.8% and 17.5% of patients with Type 1 diabetes with and without necrobiosis lipoidica, respectively, had elevated thyroid antibodies (P = 0.051). Necrobiosis lipoidica was correlated with coeliac disease in patients with Type 1 diabetes (3.4% vs. 1.0%; P = 0.0035).

CONCLUSIONS

Our data indicate a strong correlation between hyperglycaemia and the development of necrobiosis lipoidica. We postulate that the underlying pathogenic processes differ from those leading to microalbuminuria and retinopathy, and additional immunological mechanisms may play a role.

[Necrobiosis lipoidica. Variants on a theme]

A 69-year-old patient presented with different skin lesions all of which belonged to group of necrobiosis lipoidica. The initial histologic diagnosis was actinic granuloma O'Brien. A subsequent biopsy was interpreted as granulomatous necrobiosis lipoidica. The history of these necrobiotic variants is reviewed and exemplarily depicted with this case. Necrobiosis lipoidica is part of the spectrum of granulomatous skin disorders. Although its etiology is unclear, an association with diabetes mellitus is often discussed. Multiple therapeutic options exist, but standardized guidelines for treatment are missing.

Detection of spirochaetal microorganisms by focus floating microscopy in necrobiosis lipoidica in patients from central Europe

AIMS

Necrobiosis lipoidica (NL) is a chronic inflammatory skin disease with unknown aetiology. The aim was to determine the presence of spirochaetal microorganisms in NL.

METHODS AND RESULTS

Focus-floating microscopy (FFM) is a modified immunohistochemical technique that was developed to detect borrelial spirochaetes within tissue sections. It has proven to be more sensitive for the detection of spirochaetes than polymerase chain reaction (PCR). Fifty-six cases of NL as well as 44 negative and 33 positive controls were investigated for the presence of Borrelia within tissue specimens. Using FFM, Borrelia could be detected in 42 cases (75.0%) and were seen significantly more often in histologically active inflammatory-rich (38/41, 92.7%) than in inflammatory-poor (4/15, 26.7%) cases of NL (P < 0.001). Seven cases investigated with a Borrelia-specific PCR (23s-RNA) remained negative. In contrast, FFM was positive in 30 of 33 (90.9%) positive controls of acrodermatitis chronica atrophicans and 15 of the positive controls (45.5%) were also positive with PCR, whereas no negative controls revealed any microorganisms.

CONCLUSIONS

Detection of spirochaetes in NL points to a specific involvement of B. burgdorferi or other similar strains in the development of or trigger for this disease.

Evidence for intramolecular B-cell epitope spreading during experimental immunization with an immunogenic thyroglobulin peptide

Thyroglobulin (Tg) is a target autoantigen in autoimmune thyroid diseases, such as Graves' disease (GD) and Hashimoto's thyroiditis. In a previous study we identified three 20mer Tg peptides bearing epitopes of autoantibodies associated with GD (TgP15, TgP26 and TgP41: sequences 2339-2358, 2471-2490 and 2651-2670 of human Tg, respectively). In the present study, we investigated the antigenicity of the above peptides in experimental immunization with Tg, the immunogenicity of antigenic peptides and the possibility of intramolecular B-cell epitope spreading during peptide immunization. For this purpose, two rabbits were injected with human Tg in CFA six times, every three weeks. Two control animals were injected only with CFA. Testing of antisera and of affinity-purified antibodies, by ELISA against the three peptides, revealed reactivity only to TgP41. This synthetic peptide was subsequently administered to two rabbits, in its free form (100 micro g in CFA six times, every two weeks). A strong serological response was developed not only against TgP41, but also to intact human and rabbit Tg. Immunization with TgP41 induced intramolecular B-cell epitope spreading, i.e. production of antibodies to sites on Tg other than that corresponding to TgP41, as revealed by immunoadsorption and competitive ELISA. Histopathological studies did not reveal any infiltration in thyroid glands. We conclude that peptide TgP41 encompasses not only an epitope of disease-associated autoantibodies, but also a dominant immunogenic epitope of experimentally induced Tg-specific antibodies, able to drive B-cell epitope spreading.

Unilateral necrobiosis lipoidica of the ischemic limb--a case report

A 63-year-old diabetic woman presented with new-onset intermittent claudication of the right calf accompanied by ipsilateral necrobiosis lipoidica (NL). The latter presented the typical appearance of oval, indurated plaques, with brownish-red margins and central atrophy, scattered over the right thigh and calf. Arteriography demonstrated severe obstructive lesions on the right femoral artery. NL and claudication spared the left leg. A possible ischemic pathogenesis of NL emerges from this observation and is supported by recent studies in the literature.

Treatment of necrobiosis lipoidica with topical psoralen plus ultraviolet A

BACKGROUND

Necrobiosis lipoidica (NL) is a rare skin disease, mostly seen on the legs and often occurring in patients with diabetes mellitus. The disease belongs to the idiopathic cutaneous palisading granulomatous dermatitides associated with a degeneration of collagen, thus leading to skin atrophy. Application of topical corticosteroids is the most widely used treatment but the results are not always satisfactory and may worsen skin atrophy. Preliminary studies in patients with NL have shown a clinical response with psoralen plus ultraviolet (UV) A (PUVA). Objectives To study the effect of topical PUVA on NL in a multicentre prospective study.

METHODS

Thirty patients (27 women and three men) including 13 with insulin-dependent diabetes mellitus, with a diagnosis of NL proven by histopathology, were included. All patients had been unsuccessfully treated with topical and/or intralesional corticosteroids. Patients were treated twice weekly with an aqueous gel containing 0.005% psoralen followed by irradiation with UVA. Clinical photographs were taken for evaluation. In addition, 20-MHz high-frequency ultrasound analysis was performed in 10 patients to evaluate the thickness and density of the dermis during topical PUVA therapy.

RESULTS

Five patients (17%) showed complete clearing (healing of ulceration and disappearance of erythema) after a mean of 22 exposures (range 15-30). Eleven patients (37%) showed improvement, defined as healing of ulceration and/or reduction of erythema, after a mean of 23 exposures (range 11-42). Ten patients (33%) showed no effect and four patients (13%) worsened during topical PUVA therapy. The treatment results of the patients who suffered from diabetes mellitus were not different from those who did not have diabetes mellitus. No difference was seen in mean dermal thickness (1666 vs. 1706 micro m) and density (17 vs. 16 units) before and after topical PUVA therapy. Side-effects were seen in 10 patients: hyperpigmentation (n = 4), blistering (n = 4) and bacterial infection (n = 2).

CONCLUSIONS

Topical PUVA may be a useful treatment modality for NL in patients not responding to topical or intralesional corticosteroids.

Transglutaminases in disease

Transglutaminases (TGases) are enzymes that are widely used in many biological systems for generic tissue stabilization purposes. Mutations resulting in lost activity underlie several serious disorders. In addition, new evidence documents that they may also be aberrantly activated in tissues and cells and contribute to a variety of diseases, including neurodegenerative diseases such as Alzheimer's and Huntington's diseases. In these cases, the TGases appear to be a factor in the formation of inappropriate proteinaceous aggregates that may be cytotoxic. In other cases such as celiac disease, however, TGases are involved in the generation of autoantibodies. Further, in diseases such as progressive supranuclear palsy, Huntington's, Alzheimer's and Parkinson's diseases, the aberrant activation of TGases may be caused by oxidative stress and inflammation. This review will examine the role and activation of TGases in a variety of diseases.

Celiac disease-associated autoimmune endocrinopathies

Celiac disease (CD) is an autoimmune disorder induced by gluten intake in genetically susceptible individuals. It is characterized by the presence of serum antibodies to endomysium, reticulin, gliadin, and tissue transglutaminase. The incidence of CD in various autoimmune disorders is increased 10- to 30-fold in comparison to the general population, although in many cases CD is clinically asymptomatic or silent. The identification of such cases with CD is important since it may help in the control of type I diabetes or endocrine functions in general, as well as in the prevention of long-term complications of CD, such as lymphoma. It is believed that CD may predispose an individual to other autoimmune disorders such as type I diabetes, autoimmune thyroid, and other endocrine diseases and that gluten may be a possible trigger. The onset of type I diabetes at an early age in patients with CD, compared to non-CD, and the prevention or delay in onset of diabetes by gluten-free diet in genetically predisposed individuals substantiates this antigen trigger hypothesis. Early identification of CD patients in highly susceptible population may result in the treatment of subclinical CD and improved control of associated disorders.

Death, autoantigen modifications, and tolerance

Autoantibodies present in the serum of patients with a variety of inflammatory diseases have proven useful as diagnostic markers and as probes with which to elucidate biochemical and signaling pathways. The mechanisms governing the generation of autoantibodies remain elusive, constituting a critical missing link in our understanding of rheumatologic illnesses. Several lines of experimentation in recent years have strongly implicated events surrounding cell death in this process. This review will address the potential role played by death-specific modifications of autoantigens in bypassing tolerance to highly conserved autoantigens, including nucleic acids, lipids, and proteins.

Tissue transglutaminase: apoptosis versus autoimmunity

Autoimmune diseases are characterized by multiple autoantibodies and/or autoreactive T cells that recognize a large number of antigens. Many of these antigens undergo extensive post-translational modifications during apoptosis and act as substrates for the proapoptotic cystein proteases. Here, Mauro Piacentini and Vittorio Colizzi discuss the effects on autoimmunity produced by post-translational modifications of proteins catalysed by the proapoptotic enzyme tissue transglutaminase.