Genetic polymorphism in psoriasis: A prospective cohort study

INTRODUCTION

Psoriasis is a chronic, recurrent, immune-mediated inflammatory dermatosis driven by the activation of Th1 (T helper) and Th17 cells with hyperproduction of proinflammatory cytokines (Tumor necrosis factor–α; Interleukins – 17, 22, 23). This disease is characterized by a polygenic mode of inheritance and is triggered by environmental factors, leading to the disruption of keratinization and keratinocyte proliferation with the formation of characteristic psoriatic papules and plaques. Recent studies confirm the systemic nature of inflammation in psoriasis that affects not only the skin but also other organs and systems [1–3]. Noteworthy is that among other complex systemic diseases, psoriasis has a strong genetic component, with heritability exceeding 60% [4]. Studies in the field of molecular genetics have identified over 60 genomic loci whose polymorphisms are associated with an increased risk for psoriasis in European populations, and over 30 similar loci have been described for the Han Chinese population [5][6].

The past ten years have seen significant advances in the study of the genetic nature of psoriasis [1][5–8]. This disease has been confirmed to arise from a complex set of hereditary factors. To date, dozens of genetic variations associated with psoriasis have been discovered, including the alleles of HLA‑C (Human Leukocyte Antigens — C), HLA‑DQ, CCHCR1 (Coiled-coil alpha-helical rod protein 1), and CYP1A1 genes. Key loci such as PSORS1-9 (psoriasis susceptibility 1-9) and PSORSASI have also been identified. Although the genetic mechanisms of psoriasis are yet to be completely decoded [1][9–12], studies assessing genetic polymorphism should take into account that psoriasis, like other immune-mediated inflammatory diseases, exhibits the strongest association with HLA genes [13].

In the European population, the correlation with the HLA‑C*06 allele is more pronounced, whereas in individuals of Asian descent, the association with the HLA‑C*01 allele is more commonly detected. Studies by Yi-Wei Huang and Tsen-Fang Tsai show the diverse nature of psoriasis pathogenesis and C*06 allele frequency in different racial groups, indicating the need for further research to confirm the significance of the HLA‑C*06 and HLA‑C*01 alleles in the development of psoriasis [5].

The results of studies [14–19] suggest an association of the HLA‑B*27 allelic variant with both psoriatic arthritis (PsA, arthropathic psoriasis) and psoriasis. However, an analysis of clinical data shows that this genetic marker exhibits a significantly stronger association with PsA than psoriasis [20].

Thus, by assessing genetic polymorphism and linkage, it is possible to assess the frequency of haplotypes in many populations around the world and identify susceptibility genes, which contributes to the understanding of multifactorial disease pathogenesis, early decision-making regarding patient management and treatment, and the development of molecular medicine, namely predictive medicine characterized by its individualized approach and preventive focus.

Open literature contains relatively little data on the polymorphism of genes associated with psoriasis, as well as comorbid and concomitant diseases in the large and multinational Russian population.

The study aims to perform the typing of HLA‑C*06 and HLA‑B*27 allelic variants in moderate-to-severe psoriasis patients residing in St. Petersburg.

METHODS

Study design

A prospective cohort study of 165 moderate-to-severe psoriasis patients residing in St. Petersburg was conducted. All study participants underwent allele-specific genotyping: identification of the HLA‑C*06 and HLA‑B*27 alleles using the polymerase chain reaction followed by restriction fragment length polymorphism analysis (PCR-RFLP).

Study conditions

The patients were treated by a dermatologist at the clinical facilities of the North-Western State Medical University named after I.I. Mechnikov of the Ministry of Health of the Russian Federation (P.N. Kashkin Research Institute); St. Petersburg State University (Pirogov Clinic of High Medical Technologies); City Clinical Specialized Center for Dermatology and Venereology (St. Petersburg); if necessary, the patients were consulted by a general practitioner or other specialists (cardiologist, rheumatologist, gastroenterologist, endocrinologist, etc.).

The genetic research was conducted at the Laboratory of Molecular Toxicology and Experimental Therapy of the Research Institute of Hygiene, Occupational Pathology, and Human Ecology (Federal Medical-Biological Agency of Russia) in 2020–2024.

Eligibility criteria

Inclusion criteria

Age of majority (age of ≥18 years); permanent residents of St. Petersburg; clinically verified diagnosis of moderate-to-severe psoriasis (L40.0 according to ICD-10) confirmed by a dermatologist; written voluntary informed consent to participate in the study after receiving complete information about its objectives, methods, potential risks, and benefits.

Exclusion criteria

Pregnancy or lactation period (in women of childbearing age) and severe concomitant diseases: lymphoproliferative disorders (lymphomas; leukemias); Class IV chronic heart failure according to the New York Heart Association classification; end-stage chronic kidney disease, Stage 5 according to KDGO (Kidney Disease: Improving Global Outcomes); diabetes mellitus (HbA1c > 9%); active oncological diseases (except for in situ carcinomas); liver cirrhosis (Child-Pugh class C); viral hepatitis B and C (HBsAg+; HCV RNA+); HIV infection (regardless of the viral load and CD4+ level); active tuberculosis (including extrapulmonary forms); participation in other clinical studies within the previous three months.

Removal criteria

Refusal to participate in the study at any stage.

Description of eligibility criteria (diagnostic criteria)

Psoriasis was diagnosed based on characteristic clinical signs of the disease. Diagnostic and therapeutic measures were implemented as per the clinical recommendations of the Russian Ministry of Health¹ and are regulated by Order No. 924n of the Ministry of Health of the Russian Federation as of November 15, 2012, “On the Approval of the Procedure for the Provision of Medical Care in Dermatology and Venereology” (as amended in 2023).

Selection of group members

The study included 165 patients who met the established inclusion and exclusion criteria during treatment. The patients were not divided into separate groups due to the lack of clinically validated genetic markers for psoriasis patients that could be used to predict disease severity.

Target parameters in the study

Main parameters in the study

Severity of psoriasis; concomitant and comorbid conditions in psoriasis patients; allele-specific genotyping (identification of the HLA‑C*06 and HLA‑B*27 alleles).

Additional parameters in the study

Additional parameters are not provided in this study.

Methods for measuring the target parameters

In this study, the psoriasis patients underwent a clinical assessment: a standardized PASI (Psoriasis Area and Severity Index) scoring to objectively assess the skin condition; BSA (Body Surface Area) measurement to determine the area of skin lesions; DLQI (Dermatology Life Quality Index) calculation to analyze the impact of the disease on the patients’ quality of life.

Simultaneously, gene testing was performed to detect the HLA‑C*06 and HLA‑B*27 alleles using a real-time PCR, followed by an analysis of amplification products. Biomaterial for genotyping was collected in K3-EDTA vacutainers to stabilize genomic DNA. After centrifugation at 1000 g for ten minutes, the samples were divided into aliquots, frozen, and stored at −70°C in a freezer until DNA extraction. Genomic DNA was extracted from cryopreserved samples of whole peripheral blood using the Diatom™ DNA Prep kit (Galart Diagnostikum, Russia). Cell lysis was performed in a buffer containing guanidine thiocyanate, followed by denaturation of cellular nucleases. The DNA-containing lysate was subjected to adsorption onto NucleoS, followed by washing with an ethanol buffer and an acetone buffer to eliminate salts. Nucleic acids were eluted using the ExtraGene E reagent. A quantitative DNA analysis was performed using a NanoDrop 2000C spectrophotometer. Concentrations were normalized to a working value of 50 ng/μL in a TE buffer (Tris-EDTA). The target loci C*06 and B*27 were amplified using PCR by means of a CFX96 amplifier (Bio-Rad, USA).

For the C*06 detection via the PCR method, a ScreenMix-HS kit (Evrogen; cat. no. PK143L) was used; the steps performed using the CFX96 amplifier are provided in Table 2.

The obtained PCR product was treated with Sma I restriction enzyme (Thermo Scientific™; cat. no. ER0662), which cleaves the obtained complementary oligonucleotides at the 5’-CCC-↓-GGG-3’ bonds. The treatment was carried out overnight (12 h) at a temperature of 30°C. The enzyme was then heat-inactivated at 65°C for 20 min (Table 3).

The amplification for the HLA‑B*27 variant was performed as detailed in Table 4.

The PCR products were analyzed via electrophoresis on a 3% agarose gel stained with ethidium bromide using a ChemiDoc gel documentation system (Bio-Rad). The presence and size of PCR products or restriction products after electrophoretic separation and staining were determined using GeneRuler Low Range DNA Ladder (Thermo Scientific, cat. no. SM1191).

Variables (predictors, confounders, and effect modifiers)

Factors that could potentially distort the results were considered the exclusion criteria in this study.

Statistical procedures

Principles behind sample size determination

The sample size was not determined in advance.

Statistical methods

The obtained data were statistically processed using Statistica 10.0 software. Quantitative indicators were checked for normality using the Shapiro—Wilk test. The results are presented as the median and interquartile range (Me [ Q1; Q3]) for quantitative variables that did not follow the normal distribution and as absolute values and percentages (n, %) for categorical variables. Differences were considered significant at p ≤ 0.05. The value p < 0.05 was considered statistically significant for all types of analysis. In order to assess the effect of genetic polymorphisms on clinical outcomes in psoriasis, the odds ratio (OR, 95% CI, p) and relative risk (RR, 95% CI, p) were determined using database data (http://www.allelefrequencies.net/) and original research for comparison.

RESULTS

Sampling

The study group was formed to include patients diagnosed with Ps; the presence/absence of concomitant conditions and comorbidity was taken into account. No patients refused to participate in the study. A block diagram of the study design is shown in the figure.

Characteristics of the study sample (groups)

The mean age of 165 moderate-to-severe psoriasis patients was 46 years [ Q1 36; Q3 59]. The median duration of the disease was 21 years [ Q1 9; Q3 29]; the scores of indices are as follows: PASI score of 19.2 [ Q1 14.1; Q3 24.8]; DLQI score of 17 [ Q1 14; Q3 22]; BSA score of about 23% [ Q1 17; Q3 30]. Comorbidity and concomitant diseases were clinically confirmed in 141 (86%) patients.

For comparison purposes, the study used data on various Russian populations available on the portal Allele*Frequencies in Worldwide Populations (http://www.allelefrequencies.net/, as of January 30, 2025), which includes large sample sizes (over 1000 samples) and information about the number of variants of the HLA‑C (HLA‑C*06 allele) and HLA‑B genes (HLA‑B*27 allele).

Main study results

The Allele*Frequencies in Worldwide Populations portal provides representative data on the allelic variants of the HLA‑C in registered bone marrow donors from Nizhny Novgorod (1510 samples) and Karelia (1075 samples). Of 1510 registered healthy bone marrow donors (Nizhny Novgorod), nineteen homozygous carriers of the HLA‑C*06 allele (1.26%) and 303 heterozygous carriers of the HLA‑C*06 allele (20.1%) were identified. The frequency of the allelic variant in the population amounts to 321/1510 = 21.26%. In the sample of 1075 registered healthy bone marrow donors (Karelia), ten homozygous HLA‑C*06 carriers (0.93%) and 177 heterozygous HLA‑C*06 carriers (177/1075 = 16.5%) were identified. The frequency of the allelic variant is 18.3% (187/1075 = 17.4%).

Data from the Russian Research Institute of Hematology and Transfusion Medicine of the Federal Medical-Biological Agency shows that in the polyethnic donor population (n = 2853) of the Northwest Region, the HLA‑C*06:02 and HLA‑B*27 allele frequencies amounted to 11.3% (322 carriers) and 5.3% (150 carriers), respectively [21].

A genotyping of 3485 bone marrow/hematopoietic stem cell donors conducted at the National Medical Research Center for Hematology of the Ministry of Health of the Russian Federation revealed that in this sample where 3345 (95.7%) donors self-identified as Russian, 134 (3.8%) were representatives of other ethnic groups, and 16 (0.5%) did not indicate their ethnicity, the HLA‑B*27 and HLA‑C*06:02 frequencies amounted to 5.2% (174 allele carriers) and 11.7% (391 carriers), respectively [22].

It can, therefore, be said that the frequencies of target allelic variants in Moscow and St. Petersburg are approximately the same.

An allele distribution analysis for polymorphic HLA‑C*06 loci (HLA‑C gene) found that 44% (73 cases) of the examined psoriasis patients (n = 165) carried the HLA‑C*06 allele, while the HLA‑B*27 allele was identified in 16% of the examined patients (26 cases). In addition, a combined carriage of both alleles was observed in 6% of the patients (nine cases). In order to assess the statistical significance of the obtained results, data on the control group of healthy bone marrow donors (n = 2853) from the Northwest Region of Russia were used. The statistical analysis involved calculating the odds ratio with the determination of relative risk and construction of 95% confidence intervals (Table 5).

A significant association between the HLA‑C*06 allele and psoriasis development was found. In the carriers of this allelic variant, the odds ratio and relative risk amounted to 6.24 (CI: 4.49–8.66; p < 0.001) and 5.27 (CI: 3.95–7.03; p < 0.001), respectively. This is consistent with the literature data on the high associative strength of this allele in psoriasis [7]. Some authors note that in psoriasis, the HLA‑C*06 allele is present in 60% of cases in studies mapping recombinant haplotypes, which points to the C*06 allele as the main genetic determinant of susceptibility to psoriasis [23]. In this study, the C*06 frequency in patients with moderate-to-severe forms of the disease significantly exceeded the corresponding indicators in the control populations: by 2.1 times compared to the control group of healthy bone marrow donors from Nizhny Novgorod; by 2.5 times compared to the Karelian population; by 3.9 and 3.8 times compared to the polyethnic groups of donors from the Northwest Region and Moscow.

For the other allele under study, HLA‑B*27, the parameters were less pronounced: OR = 3.37 (CI: 2.15–5.29; p < 0.001); RR = 3.02 (CI: 2.05–4.46; p < 0.001). This indicates a smaller contribution of this allelic variant to the genetic predisposition to psoriasis as compared to the HLA‑C*06 allele. The proportion of HLA‑B*27 carriers among patients with moderate-to-severe forms of the disease was three times higher than the corresponding indicators for the Northwest Region and Moscow.

Scientific literature continues to debate the role of the HLA‑C*06 allele in the pathogenesis of various clinical forms of psoriasis and PsA [24–26]. Several studies [27–29] confirm the genetic homogeneity of psoriasis and PsA, reporting a similar frequency for the C*06 allele of 56–60% in the examined patients. However, other studies [30] report differences in allele distribution between these nosological entities, which is consistent with our data and confirms the hypothesis of genetic heterogeneity of psoriasis and PsA.

The obtained results are clinically significant, as they indicate the relevance of molecular genetic testing for the HLA‑C*06 and HLA‑B*27 alleles. In the early stages of the disease, HLA typing provides a means to stratify patients according to genetic risk and predict the likelihood of developing severe forms of the disease, as well as informing the optimal treatment strategy. Of particular importance is the possibility of identifying hereditary predisposition at the presymptomatic stage, which is especially relevant in multifactorial diseases with a pronounced genetic component.

Due to the systemic and multifactorial nature of psoriasis, we assessed the multimorbidity profile of the patients. Of the 141 psoriasis patients with comorbid and concomitant conditions, PsA, hypertension, obesity, and gastritis were diagnosed in 53 (38%) patients (Table 6).

In order to characterize the genetic basis of other aspects of this disease, such as early burden of concomitant and comorbid conditions and increased risk of disability and mortality, we analyzed the association of HLA‑C*06 and/or HLA‑B*27 alleles with the estimated risk for cardiovascular diseases, PsA, and gastrointestinal tract diseases in moderate-to-severe psoriasis patients, as well as predisposition to psoriasis.

In the group of psoriasis patients, the HLA‑B*27 allele was associated with an increased risk for PsA (OR = 3.26, p = 0.0053) as compared to patients without this allelic variant (Table 7).

Thus, HLA‑B*27 identification increases the predictive value of evaluated risk for PsA in psoriasis patients (RR = 3.26, p = 0.0053), which confirms the clinical significance of HLA typing for this allelic variant for the stratification of patients according to the degree of genetic risk. Early identification of the HLA‑B*27 allele will enable the timely referral of patients at high risk for PsA to a rheumatologist for follow-up. Early genotyping for informative alleles can optimize the selection of a patient management strategy.

The performed analysis also revealed that the group of psoriasis patients without the HLA‑B*27 and HLA‑C*06 alleles (HLA‑B*27(-)/HLA‑C*06(-) genotype) had a 2.04-time higher likelihood of developing cardiovascular pathology (hypertension) as compared to other genotypic groups (Table 8).

The studies [31] report a high probability of diagnosing concomitant and comorbid diseases in psoriasis patients, indicating a significantly increased risk for cardiovascular pathology as compared to other diseases of organs and systems. The study results indicate that psoriasis patients without both the HLA‑B*27 and HLA‑C*06 alleles are over twice as likely to have concomitant cardiovascular pathology as patients carrying other combinations of these alleles in the genotype (p = 0.036). In other words, in psoriasis patients, cardiovascular pathology is not associated with the studied allelic variants of the major histocompatibility complex; however, this does not exclude the possibility of identifying specific genetic variants associated with cardiovascular pathology in further studies.

Additional study results

No additional results were obtained during the study.

DISCUSSION

Summary of the main study result

The study results show the clinical significance of identifying the HLA‑C*06 allelic variant in the initial diagnostics of psoriasis. The obtained data indicate the importance of HLA‑typing this locus in the early stages of the disease, which can help predict the severity of the pathological process and make an informed choice of the best treatment strategy. The performed molecular genetic analysis revealed a significant association between the HLA‑B*27 allele and the development of PsA (OR = 3.26; 95% CI: 1.42–7.51), confirming the importance of including this genetic marker in the examination algorithm for psoriasis.

An analysis of allele distribution in the study group showed that HLA typing of the HLA‑B*27 and HLA‑C*06 loci is recommended in the initial diagnostics of psoriasis. This can help identify patients at high genetic risk for PsA; identify the risk group for arterial hypertension (OR = 2.04, 95% CI: 1.08–3.87); develop a personalized plan for follow-up and pathogenetic therapy.

Research limitations

The study has limitations related to low statistical power due to the small sample size of patients who underwent genotyping for the HLA‑C*06 and HLA‑B*27 alleles.

Interpretation of the study results

Based on the existing foreign data on the association of the HLA‑C*06 and HLA‑B*27 alleles with psoriasis [11–13][28–30], the study results confirm a significant association of the HLA‑C*06 allele with the risk of disease development in the study group of psoriasis patients residing St. Petersburg (RR = 5.27; 95% CI: 3.95–7.03; p < 0.001). The obtained data are consistent with the results of Russian studies, which also report the frequency of the HLA‑C*06 allele as a genetic factor for psoriasis [7]. In the study, the proportion of C*06 carriers among moderate-to-severe psoriasis patients in St. Petersburg was 2.1 and 2.5 times higher than the corresponding indicators in the control populations of healthy bone marrow donors in Nizhny Novgorod and Karelia, respectively. The data obtained for the B*27 allele are consistent with the articles [21][22]: its frequency was significantly lower than that of C*06.

A number of studies [32] confirm that the HLA‑B*27 allele serves as a marker of risk for PsA, while the HLA‑C*06 allele is a risk factor for psoriasis. The studies also report that psoriasis patients whose first-degree relatives have PsA are at a higher risk of developing the disease [33–35]. The present study shows the significance of genotyping psoriasis patients for the HLA‑B*27 allele to predict the likelihood of PsA that increases the risk of disability. The presence of the HLA‑B*27 allele in psoriasis patients statistically significantly increases the chances of developing PsA (OR = 3.26; p = 0.0070).

The study revealed no significant association between the HLA alleles (B*27 and C*06) and the presence of hypertension in psoriasis patients. However, the group of patients without B*27(-)/C*06(-) was found to be more likely to have cardiovascular pathology (hypertension) than individuals who carried the analyzed alleles of the HLA‑B and/or HLA‑C genes. Given the high prevalence of cardiovascular disease in psoriasis, the search for specific genetic markers remains relevant.

CONCLUSION

The genetic predisposition of psoriasis patients largely determines disease development and comorbidity risks. Early genotyping for informative alleles can optimize the selection of a patient management strategy. The genotyping of psoriasis patients for HLA‑C*06 and HLA‑B*27 alleles can help predict the severity of the disease, as well as anticipate multimorbidity and refer patients to specialists for further consultation. The study results can be extended to other types of research. In particular, genotyping for other genes in patients with psoriasis or another chronic dermatosis can be used both to evaluate patient management strategies and to diagnose comorbid and concomitant conditions.