Mechanisms of Disease: Psoriasis.

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(07)61128-3.pdf

Pathogenesis and clinical features of psoriasis.

Psoriasis is a common chronic, recurrent, immune mediated disease of the skin and joints. It can have a significant negative impact on the physical, emotional, and, psychosocial wellbeing of affected patients. Psoriasis is found worldwide but the prevalence varies among different ethnic groups. It has a strong genetic component but environmental factors such as infections can play an important role in the presentation of disease. There are several clinical cutaneous manifestations of psoriasis but most commonly the disease presents as chronic, symmetrical, erythematous, scaling papules and plaques. The epidemiology, clinical features, and impact on quality of life of psoriasis are reviewed.

https://ard.bmj.com/content/annrheumdis/64/suppl_2/ii18.full.pdf

Psoriasis: epidemiology, clinical features, and quality of life

Animal life is controlled by neurons and in this setting cholinergic neurons play an important role. Cholinergic neurons release ACh, which via nicotinic and muscarinic receptors (n- and mAChRs) mediate chemical neurotransmission, a highly integrative process. Thus, the organism responds to external and internal stimuli to maintain and optimize survival and mood. Blockade of cholinergic neurotransmission is followed by immediate death. However, cholinergic communication has been established from the beginning of life in primitive organisms such as bacteria, algae, protozoa, sponge and primitive plants and fungi, irrespective of neurons. Tubocurarine- and atropine-sensitive effects are observed in plants indicating functional significance. All components of the cholinergic system (ChAT, ACh, n- and mAChRs, high-affinity choline uptake, esterase) have been demonstrated in mammalian non-neuronal cells, including those of humans. Embryonic stem cells (mice), epithelial, endothelial and immune cells synthesize ACh, which via differently expressed patterns of n- and mAChRs modulates cell activities to respond to internal or external stimuli. This helps to maintain and optimize cell function, such as proliferation, differentiation, formation of a physical barrier, migration, and ion and water movements. Blockade of n- and mACHRs on non-innervated cells causes cellular dysfunction and/or cell death. Thus, cholinergic signalling in non-neuronal cells is comparable to cholinergic neurotransmission. Dysfunction of the non-neuronal cholinergic system is involved in the pathogenesis of diseases. Alterations have been detected in inflammatory processes and a pathobiologic role of non-neuronal ACh in different diseases is discussed. The present article reviews recent findings about the non-neuronal cholinergic system in humans.

https://bpspubs.onlinelibrary.wiley.com/doi/pdf/10.1038/bjp.2008.185

Acetylcholine beyond neurons: the non-neuronal cholinergic system in humans.

Hidradenitis suppurativa, also known as acne inversa, is a chronic, often debilitating disease primarily affecting the axillae, perineum, and inframammary regions. Prevalence rates of up to 4% have been estimated. Our understanding of the disease has changed over time. It is now considered a disease of follicular occlusion rather than an inflammatory or infectious process of the apocrine glands. Clinically, the disease often presents with tender subcutaneous nodules beginning around puberty. The nodules may spontaneously rupture or coalesce, forming painful, deep dermal abscesses. Eventually, fibrosis and the formation of extensive sinus tracts may result. The location of the lesions may lead to social embarrassment and the failure to seek medical treatment. Therapies in the past have consisted of long-term antibiotics, antiandrogens, and surgery. New treatments like tumor necrosis factor-alfa inhibitors have given clinicians more options against this difficult disease.

https://www.jaad.org/article/S0190-9622(09)00036-X/pdf

Hidradenitis suppurativa: A comprehensive review

The PSORS1 locus in the major histocompatibility complex region is the major genetic determinant for psoriasis vulgaris. Within the PSORS1 region reside at least three potential candidate genes for psoriasis susceptibility. Specific allelic variants of the genes HLA-Cw*6, HCR*WWCC, and CDSN*5 are strongly associated with psoriasis vulgaris and are in strong linkage disequilibrium with each other. We have genotyped the three psoriasis vulgaris susceptibility alleles of the PSORS1 locus in two clinical variants of psoriasis (guttate psoriasis and palmoplantar pustulosis) to study whether PSORS1 is also involved in the pathogenesis of these variants. We also asked whether these two clinical subgroups could help us to distinguish the causative gene within the high-risk PSORS1 haplotype. The association of guttate psoriasis with the three PSORS1 susceptibility alleles was similar and even stronger than seen with psoriasis vulgaris. Palmoplantar pustulosis, however, did not show association with any of the three candidate genes at this locus. Finally, no correlation with the age of onset for disease was observed. Our results show conclusively that psoriasis vulgaris and guttate psoriasis have a similar genetic basis for their association to PSORS1, whereas palmoplantar pustulosis appears to be a distinct disorder.

Genetic Analysis of PSORS1 Distinguishes Guttate Psoriasis and Palmoplantar Pustulosis

In a previous screening study, 16% of patients with psoriasis had IgA and/or IgG antibodies to gliadin (AGA). The aim of the present study was to evaluate the effect of a gluten-free diet (GFD) in 33 AGA-positive and six AGA-negative psoriasis patients. Of the 33 AGA-positive patients, two had IgA antibodies to endomysium (EmA) and 15 an increased number of lymphocytes in the duodenal epithelium, but in some this increase was slight. Two patients had villous atrophy. A 3-month period on a GFD was followed by 3 months on the patient's ordinary diet. The severity of psoriasis was evaluated with the psoriasis area and severity index (PASI). The examining dermatologists were unaware of the EmA and duodenal biopsy results throughout the study. Thirty of the 33 patients with AGA completed the GFD period, after which they showed a highly significant decrease in mean PASI. This included a significant decrease in the 16 AGA-positive patients with normal routine histology in duodenal biopsy specimens. The AGA-negative patients were not improved. After GFD, the AGA values were lower in 82% of those who improved. There was a highly significant decrease in serum eosinophil cationic protein in patients with elevated AGA. When the ordinary diet was resumed, the psoriasis deteriorated in 18 of the 30 patients with AGA who had completed the GFD period. In conclusion, psoriasis patients with raised AGA might improve on a GFD even if they have no EmA or if the increase in duodenal intraepithelial lymphocytes is slight or seemingly absent.

Psoriasis patients with antibodies to gliadin can be improved by a gluten-free diet

Pustulosis palmoplantaris (PPP) is a common chronic skin disease, which is very resistant to treatment. It is not known why the lesions are located in the palms and soles. There are few studies of the disease and in particular studies of the histology. Fifty-nine patients with PPP answered a questionnaire concerning their medical history and 39 of them were clinically examined. Biopsy specimens were taken from involved skin in 22 of the 39 patients and studied immunohistologically for tryptase+ mast cells, EG2+ eosinophils, lipocalin+ neutrophils and CD3+ T lymphocytes. The sweat gland and sweat duct were visualized with AE1/AE3 antibody (cytokeratins 1-8, 10, 14/15, 16, 19). In addition to neutrophils in the pustule and lymphocytes in the upper dermis, there were also large numbers of mast cells and eosinophils in the subpustular area. Numerous eosinophils were present in the pustule. The epidermal part of the eccrine duct was not detectable in any of the specimens from patients with PPP but was present in all of the nine control persons (including two smokers). The results indicate that the acrosyringium is involved in the inflammation and also that mast cells and eosinophils participate in a hitherto unknown way. Of the 39 patients clinically examined, two had previously diagnosed thyroid disease and two had gluten hypersensitivity. Seventeen had one or several abnormal serum concentrations of thyroid-stimulating hormone, thyroxin, antibodies against thyroglobulin or thyroperoxidase and 10 had immunoglobulin (Ig) A antibodies to gliadin. The mean +/- SD for serum IgA and for eosinophil cationic protein was increased. From the questionnaire the most notable finding was that 56 of the 59 patients had been or still were smokers, all of whom had started smoking before the first signs of PPP. We hypothesize that the acrosyringium might be the target for the inflammation and that PPP is linked to autoimmune thyroid disease and smoking.

Palmoplantar pustulosis: a clinical and immunohistological study.

Recent findings about the pathogenesis of pustulosis palmaris et plantaris (PPP), also known as palmoplantar pustulosis, suggest that IL-17 expression in the acrosyringium as well as infiltration of IL-17 positive cells, e.g. Langerhans cells may play important roles. However, to date, it has not been established whether circulating IL-17 related cytokines are involved in PPP. We studied the circulating IL-17 related cytokines as well as the mRNA levels in lesional skin. IL-17 related cytokine mRNAs were increased in the PPP lesions compared with the control tissues (five patients vs five controls). The serum levels of TNF-alpha, IL-17, IL-22 and IFN-gamma also were significantly increased in PPP, but not IL-23 and IL-8 (48 patients vs 20 controls). Our findings document that not only the serum IL-17 but also tissue IL-17 are elevated in PPP and may be in the pathogenesis of this disorder.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-0625.2011.01325.x

Patients with palmoplantar pustulosis have increased IL-17 and IL-22 levels both in the lesion and serum.

Background A suggested role for nicotine in the pathogenesis of palmoplantar pustulosis (PPP) has been discussed. The target for the inflammation in PPP is the acrosyringium. Nicotine acts as an agonist on nicotinic acetylcholine receptors (nAChRs) and can influence a variety of cellular functions. Objectives To study the alpha 3- and alpha 7-nAChR expression in palmar skin of patients with PPP in comparison with that in healthy smoking and non-smoking controls. Methods Biopsies from 20 patients with PPP, seven healthy smokers and eight healthy non-smokers were studied by immunohistochemistry with a monoclonal anti-alpha 3 and a polyclonal anti-alpha 7 antibody. Results In healthy controls both nAChR subtypes showed stronger immunoreactivity in the eccrine glands and ducts than in the epidermis. The papillary endothelium was positive for both subtypes. Epidermal alpha 3 staining was stronger and that of the coil and dermal ducts weaker in healthy smokers than in healthy non-smokers. In involved PPP skin, granulocytes displayed strong alpha 3 immunoreactivity. The normal epidermal alpha 7 staining pattern was abolished in PPP skin and was replaced by strong mesh-like surface staining, most markedly adjacent to the acrosyringium, which in controls was intensely alpha 7 positive at this level. Endothelial alpha 7 staining was stronger in PPP skin than in the controls. Conclusions Smoking can influence nAChR expression. The altered nAChR staining pattern in PPP skin may indicate a possible role for nicotine in the pathogenesis of PPP. We hypothesize that there is an abnormal response to nicotine in patients with PPP, resulting in inflammation.

Eva Hagforsen

Papers

Genetic Analysis of PSORS1 Distinguishes Guttate Psoriasis and Palmoplantar Pustulosis

Psoriasis patients with antibodies to gliadin can be improved by a gluten-free diet

Palmoplantar pustulosis: a clinical and immunohistological study.

Patients with palmoplantar pustulosis have increased IL-17 and IL-22 levels both in the lesion and serum.

Expression of nicotinic receptors in the skin of patients with palmoplantar pustulosis.