【作者】 王培光；

【导师】 杨森； 张学军；

【作者基本信息】 安徽医科大学 ， 皮肤病与性病学， 2007， 博士

【摘要】 背景介绍遗传性秃发或少毛症是一组表现为毛发持久性部分或完全缺失的遗传性毛发疾病。该组疾病具有临床和遗传异质性,大约60种,通常出生时即发病或在婴幼儿时期开始发病,可表现为家族聚集发病或散发,遗传方式可呈常染色体显性遗传、常染色体隐性遗传、X连锁显性遗传或隐性遗传。组织病理学检查显示,受累部位的毛囊稀少或缺如和毛球萎缩。根据临床上是否伴发其他先天性异常,将遗传性秃发或少毛症分为仅有毛发异常的遗传性秃发或少毛症和伴发秃发或少毛症的遗传综合征两大类。前者包括先天性普秃/伴发丘疹性损害的先天性秃发、遗传性单纯性少毛症、遗传性头皮单纯性少毛症、常染色体隐性遗传性局限性少毛症、生长期头发松动综合征和Marie Unna型遗传性少毛症等;后者包括伴发青少年斑状萎缩的遗传性少毛症、维生素D依赖性佝偻病、少汗或有汗性外胚叶发育不良、Bazex综合征、T细胞免疫缺陷-先天性秃发-甲营养不良综合征、毛发-鼻-指(趾)综合征、念珠状发、Netherton综合征、Bjornstad综合征、Menkes综合征、软骨毛发发育不良、毛发硫营养不良综合征、Rothmund-Thomson综合征等。根据发病机制不同,遗传性秃发或少毛症可分为毛发发生异常性疾病、毛发生长周期异常性疾病和发干结构异常性疾病,如伴发青少年斑状萎缩的遗传性少毛症和常染色体隐性遗传性局限性少毛症为毛发发生异常性疾病,先天性普秃/伴发丘疹性损害的先天性秃发、维生素D依赖性佝偻病为毛发生长周期异常性疾病,念珠状发和Netherton综合征为发干结构异常性疾病。近10年来关于遗传性秃发或少毛症的分子遗传学研究取得重要进展,已经有多个致病基因位点和/或致病基因被确定,如8p21、6p21、18p11、16q22、18q12、3q26、1p21等致病基因位点和HR、CDH3、K6HF、CDSN、DSG4、LIPH基因等。然而目前仍有一些遗传性毛发疾病的遗传学基础未有阐明。目的(1)分析1例临床少见的遗传性秃发家系的临床特征;(2)对该例遗传性秃发家系进行致病基因的定位研究,并希望确定其致病基因,为将来的基因诊断和基因治疗奠定基础。方法(1)对该例遗传性秃发家系进行家系调查、组织病理学检查和扫描电镜检查,分析该家系患者的临床表型;(2)采集该例家系16个成员血样,然后对该家系进行全基因组扫描连锁分析和单倍型分析;(3)对定位区域内的所有已知基因的功能和表达情况进行分析,以期确定可能的候选基因。结果(1)该家系共调查四代38人,其中13人受累,包括男6人,女7人,每代均有发病,遗传方式符合常染色体显性遗传模式。所有患者均表现为出生时即出现额部和枕部头发局限性缺失,仅残存极少细短头发,受累部位的头皮外观正常;除2例有稀疏的眉毛外,其他患者眉毛和睫毛全部缺失,但腋毛、阴毛和体毛均正常,不伴有牙齿、指趾甲病变和出汗异常,体格发育和智力完全正常。组织病理学检查显示,先证者秃发部位的头皮毛囊非常稀少。扫描电镜显示,先证者秃发部位头发的发干外观正常,呈圆柱状,毛小皮几乎完全剥脱,近发根处出现小段纵行沟槽和纵裂;其他2例患者发干外观均正常,但毛小皮密度较正常减少。此外,该家系少毛症患者均伴发雀斑,先证者还伴发毛周角化症;(2)全基因组扫描连锁分析显示,当外显率为99.9%时,在2号染色体上遗传标记D2S2267处得到一个最大两点lod值为3.84 (重组率θ=0.00)。单倍型分析显示,该家系致病基因位于D2S287和D2S165之间28.3cM区域。结论(1)该家系为一种不伴发外胚叶发育异常的常染色体显性遗传性局限性秃发,其临床表型和遗传定位与以往文献报道的遗传性秃发或少毛症家系均不同,提示为遗传性秃发或少毛症一种新的临床类型;(2)确定遗传性秃发或少毛症新的致病基因位点2p25.1-2p23.2,表明这组疾病存在遗传异质性。更多还原

【Abstract】 Backgrounds Hereditary alopecia or hypotrichosis is a large and heterogeneous group of inherited hair disorders featuring complete or partial and permanent absence of hairs since birth or childhood. About sixty diseases are included in this group of disorders. These disorders transmit as autosomal dominant, autosomal recessive or X-linked dominant or recessive mode of inheritance. The histopathological examination of biopsy shows the decrease or absence of hair follicles and atrophy of hair bulbs. This condition may occur as an isolated defect, or as a feature of a hereditary syndrome, usually in association with other ectodermal abnormalities. The isolated hair disorders include alopecia universalis congenita or alopecia with papular lesions, hypotrichosis simplex, hypotrichosis simplex of scalp, localized autosomal recessive hypotrichosis, loose anagen syndrome and Marie Unna hereditary hypotrichosis etc. The syndromic hair disorders include hypotrichosis with juvenile macular dystrophy, vitamin D-dependent rickets, hypohidrotic or hidrotic ectodermal dysplasia, Bazex syndrome, T-cell immunodeficiency-congenital alopecia-nail dystrophy, tricho-rhino-palangeal-syndrome, monilethrix, Netherton syndrome, Bjornstad syndrome, Menkes syndrome, trichothiodystrophy, cartilage hair hypoplasia, Rothmund-Thamson syndome etc. The inherited hair disorders are classified into disorders of hair morphogenesis, hair cycling, and hair shaft structure on the basis of pathogenesis. A number of genetic loci or genes responsible for some hereditary alopecia/hypotrichosis have been identified in in recently ten years, such as 8p21, 6p21, 18p11, 16q22, 18q12, 3q26, 1p21 loci, and HR、CDH3、K6HF、CDSN、DSG4、LIPH genes.Objectives (1) to analyze the clinical features of one Chinese family with one rare clinical variant of hereditary alopecia. (2) to map the gene responsible for this type of hereditary alopecia.Methods (1) The family with hereditary localized alopecia is studied by on-the-spot investigation, histopathology, scanning electron microscopy. Then, we collect blood samples from 16 individuals and performe a genome-wide scan with 382 fluorescent microsatellite markers. Linkage software and Cyrillic software are used for linkage and haplotype analyses. Then additional ten microsatellite markers are used for fine mapping. (2) We analyze the function and expression of all known genes in the interval to determine the reasonable candidate genes.Results Thirteen of totally thirty-eight individuals in a four generation Chinese family are affected, including six males and seven females. The mode of inheritance is autosomal dominant transmission. All affected individuals present with partial absence of hairs on the frontal and occipital region of scalp at birth. The appearance of the affected scalp is normal. Moreover, all patients except individual IV6 and IV12 also present with complete absence of eyebrows and eyelashes. However, their axillary, pubic and body hairs are normal. Their teeth, nails, sweat secretion, physical or mental development is also normal. Moreover, affected individuals also have facial freckling. In the proband, individual IV7, numerous small keratinizing follicular papules are diffusely distributed on his trunk, consistent with keratosis pilaris. A punch biopsy from the proband’s affected scalp reveal strikingly decreased hair follicles with no significant inflammatory infiltrate. Scanning electron microscopy of hairs plucked from the involved area reveal complete peeling or decrease of cuticles, a longitudinal groove and fracture in the hair shaft, with normal circular appearance. (2) An autosomal dominant inheritance with 99.9% penetrance and a frequency of 0.0001 for the disease allele are assumed. We performe genome-wide scan and find a maximum LOD score from the marker D2S2667 (Zmax=3.84,θ=0.00). Haplotypes analysis suggests the gene responsible for this autosomal dominant hereditary localized alopecia lies in the 28.30 cM interval between marker D2S287 and D2S165.Conclusions (1) Our study strongly suggests that this family may represent a new clinical variant of hereditary alopecia or hypotrichosis that is clinically and genetically distinct from previously described cases. (2) We identify a novel locus of hereditary alopecia on chromosome 2p25.1-2p23.2. It indicates there is genetic heterogeneity among the hereditary alopecia or hypotrichosis.更多还原