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M. Prakash Hande - One of the best experts on this subject based on the ideXlab platform.
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Oxidative damage induced genotoxic effects in human fibroblasts from Xeroderma Pigmentosum group A patients.
The International Journal of Biochemistry & Cell Biology, 2008Co-Authors: Aloysius Poh Leong Ting, M. Prakash HandeAbstract:Xeroderma Pigmentosum A protein plays a pivotal role in the nucleotide excision repair pathway. Through site-directed binding of rigidly kinked double-stranded DNA, it verifies damaged DNA for subsequent excision and incision. Although Xeroderma Pigmentosum A-deficient cells have shown to be defective in oxidative base-lesion repair, the effects of oxidative assault on such cells have not been fully explored. Therefore, we sought to determine the involvement of Xeroderma Pigmentosum A in oxidative DNA damage-repair by treating primary fibroblasts from a patient suffering from Xeroderma Pigmentosum A with sodium arsenite and hydrogen peroxide. Our results show dose-dependent increase in genotoxicity with little change in cytotoxicity with both arsenite and H2O2 in Xeroderma Pigmentosum A-deficient cells compared to control cells. Xeroderma Pigmentosum A-deficient cells displayed increased susceptibility and reduced repair capacity when subjected to DNA damage induced by oxidative stress. Superarray results of apoptotic genes revealed differential expression of ∼10 genes between Xeroderma Pigmentosum A-deficient and normal cells following arsenite treatment. Interestingly, we noted that arsenite did not inflict as much damage in the cells compared to H2O2. Lack of functional Xeroderma Pigmentosum A seems to increase the susceptibility of oxidative stress-induced genotoxicity while retaining cell viability posing as a potential cancer risk factor of Xeroderma Pigmentosum A patients.
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Oxidative damage induced genotoxic effects in human fibroblasts from Xeroderma Pigmentosum group A patients.
The international journal of biochemistry & cell biology, 2008Co-Authors: Grace Kah Mun Low, Aloysius Poh Leong Ting, Edwin Dan Zhihao Fok, M. Prakash HandeAbstract:Xeroderma Pigmentosum A protein plays a pivotal role in the nucleotide excision repair pathway. Through site-directed binding of rigidly kinked double-stranded DNA, it verifies damaged DNA for subsequent excision and incision. Although Xeroderma Pigmentosum A-deficient cells have shown to be defective in oxidative base-lesion repair, the effects of oxidative assault on such cells have not been fully explored. Therefore, we sought to determine the involvement of Xeroderma Pigmentosum A in oxidative DNA damage-repair by treating primary fibroblasts from a patient suffering from Xeroderma Pigmentosum A with sodium arsenite and hydrogen peroxide. Our results show dose-dependent increase in genotoxicity with little change in cytotoxicity with both arsenite and H2O2 in Xeroderma Pigmentosum A-deficient cells compared to control cells. Xeroderma Pigmentosum A-deficient cells displayed increased susceptibility and reduced repair capacity when subjected to DNA damage induced by oxidative stress. Superarray results of apoptotic genes revealed differential expression of approximately 10 genes between Xeroderma Pigmentosum A-deficient and normal cells following arsenite treatment. Interestingly, we noted that arsenite did not inflict as much damage in the cells compared to H2O2. Lack of functional Xeroderma Pigmentosum A seems to increase the susceptibility of oxidative stress-induced genotoxicity while retaining cell viability posing as a potential cancer risk factor of Xeroderma Pigmentosum A patients.
Kenneth H Kraemer - One of the best experts on this subject based on the ideXlab platform.
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Reproductive Health in Xeroderma Pigmentosum: Features of Premature Aging
Obstetrics and gynecology, 2019Co-Authors: Melissa A. Merideth, Deborah Tamura, John J Digiovanna, Sikandar G Khan, Divya Angra, Joyln Ferrell, Alisa M. Goldstein, Kenneth H KraemerAbstract:To assess the age at menarche and menopause of women with Xeroderma pigmentosum, a DNA repair disease with premature aging, in a longitudinal natural history study. We conducted a natural history study that reviewed medical records for gynecologic and reproductive health of all female patients with Xeroderma pigmentosum aged older than 9 years examined at the National Institutes of Health (NIH). We performed gynecologic and laboratory examinations on a subset of the patients. Women in a second subset, who could not be examined, were interviewed using a questionnaire. Women who were deceased or lost to follow-up formed a third subset. Sixty females with Xeroderma pigmentosum aged older than 9 years (median 29 years, range 10-61 years) were evaluated at the NIH from 1971 to 2018. Of these 60, 31 had history, questionnaire, record review, and gynecologic evaluation; 14 had record review and questionnaire interview by telephone; and 15 had only NIH record review. Menarche in females with Xeroderma pigmentosum occurred at a median age of 12.0 years (range 9-17 years), which was comparable with the U.S. general population. Among the 18 patients with menopause, the median age at menopause of 29.5 years (range 18-49.5 years) was more than 20 years younger than in the U.S. general population (52.9 years). Premature menopause (before age 40 years) occurred in 14 of the 45 (31%) women aged 18 years or older, and primary ovarian insufficiency was documented in nine of them. There were 32 live births among 21 of the women, five of whom subsequently developed premature menopause. Females with Xeroderma pigmentosum in our study had a normal age at menarche and were fertile but had increased incidence of premature menopause. Premature menopause, a symptom of premature aging, should be considered for gynecologic and reproductive health as well as implicating DNA repair in maintaining normal ovarian function. ClinicalTrials.gov, NCT00001813.
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ophthalmic manifestations and histopathology of Xeroderma pigmentosum two clinicopathological cases and a review of the literature
Survey of Ophthalmology, 2011Co-Authors: Hema L Ramkumar, Deborah Tamura, John J Digiovanna, Kenneth H Kraemer, Brian P Brooks, Xiaoguang Cao, Chichao ChanAbstract:Xeroderma pigmentosum is a rare, autosomal recessive disease caused by a defect in DNA repair. Patients with Xeroderma pigmentosum often have cutaneous and ocular sun sensitivity, freckle-like skin pigmentation, multiple skin and eye cancers, and, in some patients, progressive neurodegeneration. Xeroderma pigmentosum predominantly affects the ultraviolet (UV) exposed ocular surface, resulting in eyelid atrophy and cancers, corneal dryness, exposure keratopathy, and conjunctival tumors. We report the clinical history and ocular pathology of two white women who had Xeroderma pigmentosum with neurological degeneration: Case 1 (died at age 44 years) and Case 2 (died at age 45 years). Case 1, with mutations in the XPA gene, had more than 180 basal cell carcinomas of her skin and eyelids and died from complications of neurodegeneration. Case 2, with mutations in the XPD gene, was sun-protected and had three skin cancers. She died from complications of neurodegeneration and pneumonia. Both patients had bilateral pinguecula, corneal pannus, and exposure keratopathy. Case 1 had bilateral optic atrophy, and Case 2 had bilateral peripheral retinal pigmentary degeneration. Both patients developed retinal gliosis. The ophthalmic manifestations and pathology of Xeroderma pigmentosum are discussed and reviewed with respect to this report and other cases in the literature. These cases illustrate the role of DNA repair in protection of the eyes from UV damage and neurodegeneration of the retina.
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Hypersensitivity of Xeroderma pigmentosum cells to dietary carcinogens
Mutation Research\ dna Repair Reports, 2003Co-Authors: Miroslava Protić-sabljić, David B. Whyte, Kenneth H KraemerAbstract:Abstract Xeroderma pigmentosum patients, in addition to ultraviolet-induced skin cancers, have an increased prevalence of neoplasms occuring in sites shielded from ultraviolet radiation. We postulated that these internal neoplasms might be related to ingestion of dietary carcinogens. As model dietary carcinogens, we studied the tryptophan pyrolysis products, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 3-amino-1-methyl-5H-pyrido[4,3-b]indole (Trp-P-2). These dietary compounds bind to DNA and are highly mutagenic and carcinogenic. Cytotoxicity of these compounds was examined in cultured lymphoblastoid cell lines from Xeroderma pigmentosum patients in complementation groups A, B, C, D and E and the variant form and from normal donors. All Xeroderma pigmentosum lymphoblastoid cell lines showed a greater reduction in viable cell concentration than the 2 normal lymphoblastoid cell lines following addition of Trp-P-1 or Trp-P-2 (5 μg/ml) to the culture medium. Possible differences in cellular activation of these compounds were overcome by treating the cells with rat-liver microsome-activated Trp-P-2. There was a greater reduction in viable cell concentration in the Xeroderma pigmentosum group A and D cells than in the normal lymphoblastoid cell lines after treatment with activated Trp-P-2. These data suggest that the Xeroderma pigmentosum DNA-repair system is defective in repairing Trp-P-1 and Trp-P-2 induced DNA damage in addition to being defective in repairing ultraviolet-induced DNA damage. Thus Xeroderma pigmentosum patients may be at increased risk of toxicity from some dietary carcinogens.
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Impaired ultraviolet-B-induced cytokine induction in Xeroderma pigmentosum fibroblasts.
Journal of Investigative Dermatology, 2001Co-Authors: Hirotake Suzuki, Waseem Kalair, Gulner M. Shivji, Binghe Wang, Pamela Toto, Paolo Amerio, Kenneth H Kraemer, Daniel N. SauderAbstract:Xeroderma pigmentosum is a rare, autosomal recessive disease in which patients develop excessive solar damage at an early age and have a 1000-fold increased risk of developing cutaneous neoplasms. Xeroderma pigmentosum can be classified into seven complementation groups (A-G) with defects in different DNA nucleotide excision repair genes. Xeroderma pigmentosum patients also have impaired immune function including reduced natural killer cell activity and impaired induction of interferon-γ. We hypothesized that altered cytokine induction may contribute to the immune defect in Xeroderma pigmentosum patients. We examined cytokine mRNA expression after ultraviolet B irradiation using reverse transcriptase polymerase chain reaction in fibroblasts derived from five Xeroderma pigmentosum patients in complementation groups A, C, and D and in complemented XP-A and XP-D cells. Cytokines interleukin-1β and interleukin-6 displayed impaired ultraviolet B induction whereas interleukin-8 had normal induction in the Xeroderma pigmentosum fibroblasts. Stable complementation of XP-A and XP-D cell lines increased ultraviolet-B-induced interleukin-1β and interleukin-6 expression. These results demonstrate a deficient response of Xeroderma pigmentosum fibroblasts to ultraviolet B in terms of cytokine interleukin-1β and interleukin-6 induction but normal interleukin-8 induction and exhibit a role for DNA repair in cytokine induction.
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Impaired ultraviolet-B-induced cytokine induction in Xeroderma pigmentosum fibroblasts.
The Journal of investigative dermatology, 2001Co-Authors: Hirotake Suzuki, Waseem Kalair, Gulner M. Shivji, Binghe Wang, Paolo Amerio, Kenneth H Kraemer, Paola Toto, Daniel N. SauderAbstract:Xeroderma pigmentosum is a rare, autosomal recessive disease in which patients develop excessive solar damage at an early age and have a 1000-fold increased risk of developing cutaneous neoplasms. Xeroderma pigmentosum can be classified into seven complementation groups (A-G) with defects in different DNA nucleotide excision repair genes. Xeroderma pigmentosum patients also have impaired immune function including reduced natural killer cell activity and impaired induction of interferon-gamma. We hypothesized that altered cytokine induction may contribute to the immune defect in Xeroderma pigmentosum patients. We examined cytokine mRNA expression after ultraviolet B irradiation using reverse transcriptase polymerase chain reaction in fibroblasts derived from five Xeroderma pigmentosum patients in complementation groups A, C, and D and in complemented XP-A and XP-D cells. Cytokines interleukin-1beta and interleukin-6 displayed impaired ultraviolet B induction whereas interleukin-8 had normal induction in the Xeroderma pigmentosum fibroblasts. Stable complementation of XP-A and XP-D cell lines increased ultraviolet-B-induced interleukin-1beta and interleukin-6 expression. These results demonstrate a deficient response of Xeroderma pigmentosum fibroblasts to ultraviolet B in terms of cytokine interleukin-1beta and interleukin-6 induction but normal interleukin-8 induction and exhibit a role for DNA repair in cytokine induction.
Aloysius Poh Leong Ting - One of the best experts on this subject based on the ideXlab platform.
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Oxidative damage induced genotoxic effects in human fibroblasts from Xeroderma Pigmentosum group A patients.
The International Journal of Biochemistry & Cell Biology, 2008Co-Authors: Aloysius Poh Leong Ting, M. Prakash HandeAbstract:Xeroderma Pigmentosum A protein plays a pivotal role in the nucleotide excision repair pathway. Through site-directed binding of rigidly kinked double-stranded DNA, it verifies damaged DNA for subsequent excision and incision. Although Xeroderma Pigmentosum A-deficient cells have shown to be defective in oxidative base-lesion repair, the effects of oxidative assault on such cells have not been fully explored. Therefore, we sought to determine the involvement of Xeroderma Pigmentosum A in oxidative DNA damage-repair by treating primary fibroblasts from a patient suffering from Xeroderma Pigmentosum A with sodium arsenite and hydrogen peroxide. Our results show dose-dependent increase in genotoxicity with little change in cytotoxicity with both arsenite and H2O2 in Xeroderma Pigmentosum A-deficient cells compared to control cells. Xeroderma Pigmentosum A-deficient cells displayed increased susceptibility and reduced repair capacity when subjected to DNA damage induced by oxidative stress. Superarray results of apoptotic genes revealed differential expression of ∼10 genes between Xeroderma Pigmentosum A-deficient and normal cells following arsenite treatment. Interestingly, we noted that arsenite did not inflict as much damage in the cells compared to H2O2. Lack of functional Xeroderma Pigmentosum A seems to increase the susceptibility of oxidative stress-induced genotoxicity while retaining cell viability posing as a potential cancer risk factor of Xeroderma Pigmentosum A patients.
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Oxidative damage induced genotoxic effects in human fibroblasts from Xeroderma Pigmentosum group A patients.
The international journal of biochemistry & cell biology, 2008Co-Authors: Grace Kah Mun Low, Aloysius Poh Leong Ting, Edwin Dan Zhihao Fok, M. Prakash HandeAbstract:Xeroderma Pigmentosum A protein plays a pivotal role in the nucleotide excision repair pathway. Through site-directed binding of rigidly kinked double-stranded DNA, it verifies damaged DNA for subsequent excision and incision. Although Xeroderma Pigmentosum A-deficient cells have shown to be defective in oxidative base-lesion repair, the effects of oxidative assault on such cells have not been fully explored. Therefore, we sought to determine the involvement of Xeroderma Pigmentosum A in oxidative DNA damage-repair by treating primary fibroblasts from a patient suffering from Xeroderma Pigmentosum A with sodium arsenite and hydrogen peroxide. Our results show dose-dependent increase in genotoxicity with little change in cytotoxicity with both arsenite and H2O2 in Xeroderma Pigmentosum A-deficient cells compared to control cells. Xeroderma Pigmentosum A-deficient cells displayed increased susceptibility and reduced repair capacity when subjected to DNA damage induced by oxidative stress. Superarray results of apoptotic genes revealed differential expression of approximately 10 genes between Xeroderma Pigmentosum A-deficient and normal cells following arsenite treatment. Interestingly, we noted that arsenite did not inflict as much damage in the cells compared to H2O2. Lack of functional Xeroderma Pigmentosum A seems to increase the susceptibility of oxidative stress-induced genotoxicity while retaining cell viability posing as a potential cancer risk factor of Xeroderma Pigmentosum A patients.
Klaus D Teichmann - One of the best experts on this subject based on the ideXlab platform.
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Conjunctival necrobiotic granuloma in Xeroderma pigmentosum.
Cornea, 2001Co-Authors: Fenwick C. Riley, Klaus D TeichmannAbstract:PURPOSE: We report clinical and histopathologic findings of a conjunctival lesion associated with Xeroderma pigmentosum. METHODS: A Saudi girl with known Xeroderma pigmentosum presented with pain and photophobia of the right eye and an elevated temporally located perilimbal mass. RESULTS: The mass was resected successfully and has not recurred during 1-year follow-up. Histopathologic examination of the tissue showed a necrobiotic granuloma with associated histiocytic infiltration. The patient had no systemic disease, lipid was not detected in the histiocytic lesion, no Touton giant cells were present, and there was no evidence of elastolysis. CONCLUSION: Ocular malignancies occur in association with Xeroderma pigmentosum, but benign lesions that mimic a malignancy may occur.
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Conjunctival necrobiotic granuloma in Xeroderma pigmentosum.
Cornea, 2001Co-Authors: Fenwick C. Riley, Klaus D TeichmannAbstract:We report clinical and histopathologic findings of a conjunctival lesion associated with Xeroderma pigmentosum. A Saudi girl with known Xeroderma pigmentosum presented with pain and photophobia of the right eye and an elevated temporally located perilimbal mass. The mass was resected successfully and has not recurred during 1-year follow-up. Histopathologic examination of the tissue showed a necrobiotic granuloma with associated histiocytic infiltration. The patient had no systemic disease, lipid was not detected in the histiocytic lesion, no Touton giant cells were present, and there was no evidence of elastolysis. Ocular malignancies occur in association with Xeroderma pigmentosum, but benign lesions that mimic a malignancy may occur.
Jean Krutmann - One of the best experts on this subject based on the ideXlab platform.
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Xeroderma Pigmentosum: Mondscheinkinder
Journal Der Deutschen Dermatologischen Gesellschaft, 2003Co-Authors: Yared Herouy, Johannes Norgauer, Jean Krutmann, Erwin SchöpfAbstract:Das Krankheitsbild des Xeroderma Pigmentosum beruht auf einem Gendefekt im DNS-Reparatursystem und manifestiert sich bereits in der fruhen Kindheit. Beim Xeroderma Pigmentosum handelt es sich um eine seltene autosomal rezessive Genodermatose. Klinisch zeigen diese Kinder eine starke Sonnenempfindlichkeit. Patienten mit Xeroderma Pigmentosum entwickeln schwere Sonnenbrande mit der Ausbildung einer Poikilodermie in lichtexponierter Haut. Bereits in der Kindheit entwickeln sich spinozellulare Karzinome, Basaliome und maligne Melanome. Die Mehrzahl der Patienten versterben vor dem Erreichen des Erwachsenenalters aufgrund metastasierender kutaner Malignome. Genetisch wird das Xeroderma Pigmentosum in 7 Komplementationsgruppen (XP-A bis XP-G) und die Xeroderma-Pigmentosum-Variante (XP-V) unterteilt. Diagnostisch erfolgt die Zuordnung in die jeweilige Komplementationsgruppe durch Fusionierung von Xeroderma-Pigmentosum-Fibroblasten. Differentialdiagnostisch mus das Xeroderma Pigmentosum von anderen sogenannten DNS-Reparatur-Defizienz-Syndromen wie dem Cockayne-Syndrom und der Trichothiodystrophie abgegrenzt werden. Aktuell wird uber eine erfolgreiche Anwendung eines topisch applizierten DNS-Reparatur-Enzyms berichtet. Hierbei handelt es sich um eine rekombinante liposomal verkapselte T4-Endonuklease V, welche UV-induzierte Cyclobutan-Pyrimidin-Dimere repariert. In Zukunft konnte eine kausale Behandlung auf der Gentherapie basieren. Das Einschleusen eines intakten Reparaturgens, welches spezifisch das Reparaturprotein kodiert, konnte neue Moglichkeiten der Behandlung des Xeroderma Pigmentosum eroffnen. Summary Xeroderma pigmentosum is based on a genetic defect in the DNA repair system, which is diagnosed in early childhood. Xeroderma pigmentosum is a rare disorder, which is transmitted in an autosomal recessive manner. Children with Xeroderma pigmentosum display hypersensitivity to ultraviolet (UV) radiation. These patients experience serious sunburns with minimal exposure and then develop poikiloderma in the sun-exposed areas. Squamous cell carcinomas, basal cell carcinomas and malignant melanomas all appear during childhood. The majority of patients do not reach adult, but die from metastatic cutaneous malignancies. Genetically, Xeroderma pigmentosum is differentiated into 7 complementation groups (XP-A to XP-G) and the Xeroderma pigmentosum variants (XP-V). The assignment to the specific complementation group is made by fusing of Xeroderma pigmentosum fibroblasts. Xeroderma pigmentosum must be distinguished from other so-called DNA repair deficiency syndromes, including Cockayne syndrome and trichothiodystrophy. A topical DNA repair enzyme appears to be helpful. A recombinant liposomal encapsulated T4 endonuclease V repairs UV-induced cyclobutane-pyrimidine dimers. Direct curative treatment of Xeroderma pigmentosum could be achieved with gene therapy in future. Transfection of an intact repair gene which specifically codes for the missing repair protein could open new possibilities in the therapy of Xeroderma pigmentosum.
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Xeroderma Pigmentosum: Mondscheinkinder
Journal der Deutschen Dermatologischen Gesellschaft = Journal of the German Society of Dermatology : JDDG, 2003Co-Authors: Yared Herouy, Johannes Norgauer, Jean Krutmann, Erwin SchöpfAbstract:Xeroderma pigmentosum is based on a genetic defect in the DNA repair system, which is diagnosed in early childhood. Xeroderma pigmentosum is a rare disorder, which is transmitted in an autosomal recessive manner. Children with Xeroderma pigmentosum display hypersensitivity to ultraviolet (UV) radiation. These patients experience serious sunburns with minimal exposure and then develop poikiloderma in the sun-exposed areas. Squamous cell carcinomas, basal cell carcinomas and malignant melanomas all appear during childhood. The majority of patients do not reach adult, but die from metastatic cutaneous malignancies. Genetically, Xeroderma pigmentosum is differentiated into 7 complementation groups (XP-A to XP-G) and the Xeroderma pigmentosum variants (XP-V). The assignment to the specific complementation group is made by fusing of Xeroderma pigmentosum fibroblasts. Xeroderma pigmentosum must be distinguished from other so-called DNA repair deficiency syndromes, including Cockayne syndrome and trichothiodystrophy. A topical DNA repair enzyme appears to be helpful. A recombinant liposomal encapsulated T4 endonuclease V repairs UV-induced cyclobutane-pyrimidine dimers. Direct curative treatment of Xeroderma pigmentosum could be achieved with gene therapy in future. Transfection of an intact repair gene which specifically codes for the missing repair protein could open new possibilities in the therapy of Xeroderma pigmentosum.
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Xeroderma pigmentosum und verwandte Syndrome
Hautarzt, 2002Co-Authors: Mark Berneburg, Jean KrutmannAbstract:Xeroderma pigmentosum, Cockayne-Syndrom und Trichothiodystrophie sind seltene, autosomal-rezessive Genodermatosen mit einem klinisch heterogenen Bild. Die ersten Krankheitssymptome treten in der Regel bereits im fruhen Kindesalter auf. Alle drei Erkrankungen sind durch Photosensitivitat und einen Reparaturdefekt von UV-induzierten DNS-Schaden gekennzeichnet. Ein erhohtes Hautkrebsrisiko besteht nur bei Xeroderma pigmentosum, obwohl die zugrunde liegenden Defekte zum Teil durch Mutationen im selben Gen hervorgerufen werden. Xeroderma pigmentosum, Cockayne-Syndrom und Trichothiodystrophie sind daher wichtige Modellerkrankungen fur die Pathogenese von Hauttumoren. Neuere wissenschaftliche Erkenntnisse in den Bereichen DNS-Reparatur, Transkriptionsregulation und Immunologie haben nicht nur die ursachlichen Erkrankungsmechanismen weiter aufgeklart, sondern allgemein neue Einblicke in die Entstehung von Hauttumoren gegeben. Im Folgenden sollen die klinischen Merkmale dieser Syndrome aufgezeigt und die zugrundeliegenden Mechanismen als Ursache der einzelnen Symptome verdeutlicht werden.
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Xeroderma pigmentosum und verwandte Syndrome
Der Hautarzt; Zeitschrift fur Dermatologie Venerologie und verwandte Gebiete, 2002Co-Authors: Mark Berneburg, Jean KrutmannAbstract:Xeroderma pigmentosum, trichothiodystrophy and Cockayne-syndrome are rare, autosomal recessive genodermatoses, which are clinically heterogeneous. Generally, the first signs and symptoms appear at an early age. Although all three syndromes show photosensitivity and an underlying defect in the repair of UV-induced DNA damage, only patients with Xeroderma pigmentosum have an increased skin cancer risk. The fact that all three of these syndromes can be caused by mutations in the same gene further emphasizes the role of these syndromes as an important model system for the pathogenesis of skin tumors. Recent findings in the fields of DNA repair, regulation of transcription and immunology have not only further unraveled the underlying mechanisms of these diseases but also provided important insights into the pathogenesis of skin tumors. The clinical characteristics of Xeroderma pigmentosum and related DNA repair deficiencies are reviewed with an attempt to point out direct connections between clinical signs and symptoms and their underlying mechanisms.
