Correlation Of Primary Cutaneous Amyloidosis And The Mutations Of OSMR Gene And Ultrastructural Observation

Background and Objective:Primary cutaneous amyloidosis(PCA)is a chronic pruritic skin disease in which amyloids deposit on the skin without any other organ involvement.It occurs in Southeast Asia and South America.Ten percent of PCA patients have family history.It mainly affects people in South China,including Taiwan,Guangdong,Guangxi,Hunan and Jiangxi.The pathogenesis of PCA is not clear,it may be related to scratching,ultraviolet radiation,EB virus infection,etc.so it brings difficulties to clinical treatment.PCA can be divided into lichen amyloidosis and macular amyloidosis and nodular amyloidosis.lichen amyloidosis and macular amyloidosis are the most common clinical types.The relationship between OSMR,IL-31RA,GPNMB genes and PCA have been found.OSMR mutations are the most common.There are 12 reported mutation sites in this gene.In this study,the OSMR gene P.Gly513Asp is the high frequency mutation site.Therefore,we mainly focus on the correlation between OSMR gene P.Gly513Asp and PCA clinical phenotype.Integrin alpha 6 is an essential component of hemidesmosome,which can regulate cell adhesion,differentiation,migration and apoptosis.Cells can adhere to extracellular matrix through the adhesion of integrin,which can not only maintain cell morphology but also conduct signal transduction.The purpose of this study was to explore the correlation between the clinical phenotype of primary cutaneous amyloidosis and OSMR gene mutation(p.Gly513Asp locus pure and mutation)and to observe the histological changes under transmission electron microscopy and explore the possible pathogenesis of integrin alpha 6 in PCA patients.Methods:1.The peripheral blood of 174 patients and 52 healthy controls was extracted for sanger sequence of OSMR gene exons at 11-15 and Clinical data of 174 patients with PCA were collected.The correlation between clinical phenotype and OSMR gene mutation was analyzed.2.The hemidesmosome,apoptosis of keratinocytes were observed in PCA patients and normal controls under transmission electron microscopy.3.Immunohistochemistry,TUNEL,and Immunofluorescence were used to detect the exfoliation of keratinocytes,the apoptosis of keratinocytes and the expression of connexin alpha 6,a component of hemidesmosome,in PCA patients.Results:1.Among 174 patients of PCA,35.63%had family history,64.37%had no family history,the average age of onset was 31±12.69 years old,and the peak age of onset was20-29 years old(31.03%).Among them,75.29%were LA,24.71%were MA,and the proportion of men and women in LA(75/56)and MA(16/27)had statistical difference(X~2=4.44,P=0.035).Patients with LA were more likely to have pruritus than those with MA(105/131 vs 26/43,P=0.016).2.Among 174 PCA patients,36.78%of PCA patients had OSMR gene mutation,of which 84.38%were OSMR gene p.Gly513Asp mutation site,39.06%were OSMR gene p.Gly513Asp homozygous site and 45.31%were OSMR gene p.Gly513Asp heterozygous site.Compared with the onset age of PCA patients without OSMR gene mutation(32.63±13.50),the onset age of PCA patients with OSMR gene mutation(28.58±10.90)was younger.The family history(35/64 vs 27/110,P<0.001),gender(37/64 vs 46/110,P=0.042),lesion range(16/64 vs 12/110,P=0.015)were found to be significantly different by comparing the clinical data of PCA patients between OSMR mutations(including p.Gly513Asp homozygous site,p.Gly513Asp heterozygous site,etc.)and without OSMR mutations.The family history(27/54 vs 27/110,P=0.001),gender(33/54 vs 46/110,P=0.020),lesion range(15/54 vs 12/110,P=0.006)were found to have statistical differences.The family history(27/54 vs 27/110,P=0.001),gender(33/54 vs 46/110,P=0.020),lesion range(15/54 vs 12/110,P=0.006)were found to be significantly different by comparing the clinical data of PCA patients with and without OSMR mutation.There was no significant difference in clinical typing(lichen amyloidosis and macular amyloidosis)and pruritus rate between OSMR gene mutation and non-OSMR gene mutation(P>0.05).3.Under transmission electron microscopy,apoptotic keratinocytes were observed in the spinous layer to the basal layer.The basal cell density of amyloid substance area in PCA patients was significantly lower than that in normal controls(P<0.001);The exfoliated keratinocytes and fibroblasts surrounded by amyloid substances were in the superficial dermis of PCA patients.The number of hemidesmosomes in PCA patients was significantly lower than that in the control group(P<0.001).the expression of connexin integrin alpha 6 in PCA patients was lower than in normal controls(P<0.0001).Conclusions:1)OSMR gene mutation(p.Gly513Asp homozygous site mutation)was correlated with family history,gender,lesion range and age of onset of PCA.2)The abnormal expression of connexin integrin alpha 6 may be involved in the pathogenesis of PCA by regulating the exfoliation and apoptosis of basal keratinocytes.