| Background and ObjectiveGeneralized Pustular Psoriasis (GPP) is an inflammatory skin disease and the pathogenesis of GPP is unclear. It has recently been reported that mutations in IL36RN or CARD14gene are associated with the pathogensis of GPP. The mutation alleles and rates of the two genes varied with the regions, races and occurrence of psoriasis vulgaris (PV) of the GPP patients. Systemic therapy includes acitretin, immunosuppressants, biological agents, Chinese traditional patent medicine such as tripterygium glycosides and so on. The efficiency rate of acitretin as first-line agent was79.4%compared with60%of cyclosporine A or methotrexate. Although the majority of cases of GPP associated with IL36RN mutations responding well to the above medicines, the clinical manifestations and responding to the treatment between GPP patients with and without gene mutations require further study. The aims of our study were as follo wings:(1) To clarify the incidence of IL36RN and CARD14gene mutations in Chinese GPP patients.(2) To investigate the relationship between genotype and phenotype in GPP patients and evaluate the influence of gene mutations and clinical features such as onset age of GPP, family history, severity of disease and occurance of PV in GPP patients.(3) To evaluate the influence of IL36RN c.115+6T>C mutation on transcription of IL36RN mRNA.(4) To detect serum IL-36and IL-36Ra levels in patients with GPP and PV and investigate the correlations between their levels with disease severity.Methods(1) Genomic DNA was abstracted from peripheral blood of the61GPP,48PV and186unrelated healthy controls. All the exons and flanking sequences of IL36RN and CARD14gene were amplified by PCR and products analyzed by direct sequencing.(2) The frequencies of genotypes and alleles of IL36RN c.115+6in the61GPP patients,48PV patients and186healthy controls were analyzed. The GPP patients were grouped by clinical phenotypes such as onset age of GPP, family history, severity of disease and occurance of PV in GPP patients. The relationship between genotypes and phenotypes in GPP patients were analysed by chi-square test. The patients were classified into3groups according to their gene results:definite mutation group, suspectd mutation group and none mutation group. Clinical data of patients were collected, including the onset age of GPP, WBC, hsCRP, ESR, severity of GPP, treatment effect and unique clinical features of each group. Non-parameters tests were used to compare the difference between3groups.(3) RT-PCR and direct sequencing was performed on the total RNA which was isolated from lesional skin of2patients with homozygous IL36RN c.115+6T>C mutations,2patients without mutations and1healthy control.(4) Serum IL-36and IL-36Ra levels were measured by enzyme-linked immunosorbent assay (ELISA) in45cases of GPP,34cases of PV and37healthy controls. Clinical stage and disease severity were also evaluated.Results(1)The incidence of IL36RN c.115+6T>C mutation was52.5%in Chinese GPP patients. None CARD14mutation was detected in the61Chinese GPP patients.(2) The IL36RN c.115+6T>C mutation was associated with severity of GPP, the occurrence of PV in GPP patients and had no relationship with onset age of GPP as well as family history. The hsCRP and ESR levels in the definite mutation group and suspectd mutation group were higher than the none mutation group. There was no difference of treatment response between the3groups.(3) The RT-PCR product was350bp in the2patients with homozygous IL36RN c.115+6T>C mutation in which the exon3was skipping. The RT-PCR product in the2GPP patients without IL36RN mutations and the healthy control was450bp with normal transcription of IL36RN mRNA.(4) No statistical difference of serum IL-36or IL-36Ra levels was observed among the total GPP, PV and control group. Serum IL-36β levels in the mutation group was higher than the none mutation group and serum IL-36Ra levels was the opposite especially in the pustular eruption stage. GPP patients with pustular eruption stage or high disease severity had higher serum IL-36β and y levels than healthy controls. Serum IL-36β levels had high positive correlation with serum IL-36y levels in GPP and PV patients, both of which had low positive correlation with disease severity in GPP patients.ConclusionThe incidence of IL36RN c.115+6T>C mutation was52.5%in Chinese GPP patients. CARD14gene mutation was not associated with GPP in Chinese patients. IL36RN c.115+6T>C mutation had relationship with severity of GPP and occurrence of PV in GPP patients and no relationship with the onset age and family history of GPP. There was no difference of treatment response between GPP patients with or without IL36RN mutations. IL36RN c.115+6T>C mutation was a definite mutation which may lead to the occurence of GPP. IL36RN may lead to higher serum IL-36β levels and lower IL-36Ra levels in the GPP patients with IL36RN mutations, especially in the pustular eruption stage. Serum IL-36β, γ and IL-36-Ra took part in the pathogenesis of GPP. |
