A Case Of Localized Darier’s Disease And Analysis Of Whole Exome Sequencing

Background:Darier’s disease(keratosis follicularis,DD,OMIM 124200)is a rare autosomal dominantly inherited keratinization disorder,first reported by Darier and White in 1889.DD is characterized by keratotic papules and verrucous plaques with a predilection for the seborrhoeic regions,such as head,hairline,chest,back and so on,and the flexures.V-shaped notching at the distal border of the nails,red and white longitudinal stripes may appear when nails are involved.Palmoplantar and mucous membrane may also be affected.Ultraviolet radiation,friction,high temperature,sweat,infection and other factors can aggravate the condition.DD has a variety of clinical variants,such as hypertrophic,verrucous,vesicobullous,segmental variants.Typical histopathological manifestations are dyskeratotic cells and acantholysis.Combined with the patient’s family history,greasy keratotic papules that often occur at seborrheic sites can help diagnose this disease.DD is caused by mutations in the ATP2A2 gene,located on chromosome 12q23-24.1,which encodes sarco/endoplasmic reticulum Ca2+-ATPase type 2 isoform(SERCA2),responsible for transporting calcium ions from the cytosol into the endoplasmic reticulum.Over 270 mutations in ATP2A2 gene have been identified to be related to DD,including missense,premature stop codons,and abnormal splicing.The ATP2A2 gene mutation causes decreased expression or dysfunction of SERCA2.The secondary reduced endoplasmic reticulum calcium storage can lead to abnormal intercellular adhesion(histologically characterized by acantholysis)and apoptosis(histologically characterized by corps ronds and grains),by activating endoplasmic reticulum stress.It is still unclear whether the different variants are related to special gene mutations.The ATP2A2 gene mutation has complete penetrance,but its gene expression is variable in the affected families.Objective:To identify the diagnosis and genetic characteristics of a case of localized DD,discover new mutation sites and screen the accompanied mutated genes,analyze the potential pathogenicity of the mutations by bioinformatics methods,and summarize the characteristics of other cases related to the mutations in the literature.Methods:(1)To collect the clinical information of a special case of DD with localized lesions;(2)Genetic pedigree diagram drawing:The family survey was carried out and genetic pedigree diagram was drew;(3)Dermoscopic examination:Use dermoscopy to collect the lesions’ images at 100 times and 200 times magnification;(4)Histopathological examination:Under local infiltration anesthesia,biopsy was performed on the left buttock lesions of the patient,and a skin lesion with a diameter of 6mm and a depth up to the subcutaneous fat layer was obtained for routine pathological examination;(5)Whole exome sequencing(WES):A total of 2 mL of peripheral venous blood from the patient was collected,and DNA was extracted.Library construction,library quality inspection,and sequencing were carried out after the DNA sample quality test met the standards;(6)Quality assessment and mutation site analysis of sequencing data:The raw sequencing data was filtered,checked for error rate and quality distribution to obtain the sequence conforming to the standards.Analyze the mutation data and screen the possible mutation genes and sites;(7)Bioinformatics analysis of mutation sites:Use research collaboratory for structural bioinformatics(RCSB)protein data bank(PDB),and protein structure analysis software Chimera 1.15 to predict the conformation changes of the mutant protein,and use the LOVD and UniProt database to search for other cases with the same mutation site and the same coding region mutation,and analyze their clinical characteristics.Results:(1)Clinical characteristics:The present patient has developed multiple yellowish-brown keratotic papules limited to the buttocks,covered with greasy scales,since she was about 20 years old.V-shaped defect at the free nail margin can be seen on the nails,and no mucous membrane lesions was noticed.The condition was aggravated by heat,sweating,friction,and other stimulations during the course.In this case,multiple members of the patient’s family have the disease.There is no gender difference,and the probability of suffering from the disease in the children born to the patient and the normal person is 1/2,which is consistent with the autosomal dominant inheritance(AD)in Mendelian inheritance.The other suffering members of the patient’s family developed the disease between the ages of 15-25,with skin lesions similar to this patient,but the lesions were mild.The lesions were mainly distributed in the face and neck,chest and back,groin and other parts,with repeated attacks and slight aggravation in summer.(2)Dermoscopic manifestation:Dermoscopy showed a centrally located light yellowish/brownish area(polygonal,star-like or oval morphology),surrounded by dotted/linear vessels,overlying a pinkish background(×100).Greasy brown scales surrounding hair follicle can be seen,with central adhesion and slightly upturned periphery(x200).(3)Histopathologic manifestation:Histopathology showed epidermal hyperkeratosis,focal parakeratosis,formation of fissures in the basal layer,and the presence of dyskeratotic cells in granular layer and spinous layer.(4)Results of WES:After analyzing and screening the patient’s sequencing data,38 predicted deleterious gene mutations corresponding to OMIM were found.The related diseases included hematological system diseases,endocrine diseases,nervous system diseases,visceral tumors,etc.The ATP2A2 gene mutation associated with Darier disease(OMIM 124200)was also found by screening disease-related genes using Phenolyzer website,namely c.2104G>A/p.D702N.(5)Bioinformatics analysis related to p.D702N:With RCSB PDB and protein structure analysis software Chimera 1.15,it was predicted that the spatial conformation of the protein after p.D702N mutation will change correspondingly.p.D702 is located in the hinge region that connects the ATP binding domain to the stalk domain,associated with genome variant and Ca2+ binding sites,so the mutation of p.D702 may lead to DD by decreasing the Ca2+ transport activity of SERCA2 protein.There have been 5 familial/sporadic cases caused by the p.D702N mutation in the literature.As for the Ca2+binding site mutant,a total of 7 mutations,i.e.p.I307V,p.E309K,p.N767D,p.N767del,p.N767S,p.N795S,p.E907D were found from Uniprot and LOVD databases.But the clinical manifestations caused by these mutations were different from the present patient.Conclusions:(1)According to the family history,clinical manifestations,pathological examination,and whole exome sequencing,this case was diagnosed as Darier’s disease.(2)A total of 38 deleterious gene mutations and related diseases were screened out by WES,among which the missense mutation ATP2A2 p.D702N may be related to the present case.Although 5 studies had reported the mutation in the previous literature,no similar case has been reported in China.(3)Bioinformatics analysis revealed that the mutation of p.D702N might be related to the Ca2+ binding site and genome mutation.