Xeroderma pigmentosum

Xeroderma pigmentosum in Yemen

BACKGROUND

The incidence of xeroderma pigmentosum (XP) in Yemen seems to be quite high but there are no previous reports.

OBJECTIVE

To study the clinicoepidemiologic aspect of XP in Yemen.

METHODS

All 40 patients (24 male and 16 female patients from 32 families) treated and followed between 1997 and 2014 were subjected to detailed analysis with the help of a standardized protocol. The diagnosis was based on clinical features and histopathologic data, when needed. The diagnosis of tumors was confirmed by histopathologic examination in all cases.

RESULTS

The median age of onset of initial manifestations was 9.5 months, and that of malignant lesions was 7 years. Parents of the patients were not affected, but history of consanguinity was recorded in 38. Initial lesions, such as dryness of the skin and freckles on the face, were noticed in all patients. In addition, erythema of the face with photosensitivity was observed in 21 patients. Premalignant and malignant skin lesions observed later were actinic keratosis in 15 patients, lentigo maligna in one, squamous cell carcinoma (SCC) in 10, and basosquamous carcinoma in one. Eyes were affected with SCC in seven and malignant melanoma (MM) in two patients. SCC of the lip developed in two patients and that of the tongue in one patient. Judicious use of acitretin in 12 patients showed good result.

CONCLUSION

XP in Yemen is characterized by a relatively high incidence, high percentage of consanguinity in parents of the patients, early onset of initial manifestations, malignant tumors, and severe ocular and oral lesions. Acitretin showed good result.

Ophthalmic manifestations and histopathology of xeroderma pigmentosum: two clinicopathological cases and a review of the literature

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.

Atypical fibroxanthoma and squamous cell carcinoma of the conjunctiva in xeroderma pigmentosum

Patients with xeroderma pigmentosum (XP) have defective DNA repair and a high predisposition to developing abnormalities and neoplasia in the sun-exposed areas of the skin and mucous membranes. The most common tumors reported in patients with XP are squamous cell carcinomas, basal cell carcinomas, and melanomas. Atypical fibroxanthoma (AFX) is a pleomorphic tumor that arises predominantly in the sun-damaged skin of the head and neck regions of the elderly. We describe a unique case of a 6-year-old African American boy with XP who developed an atypical fibroxanthoma and 2 squamous cell carcinomas in the conjunctiva. The clinical and histopathologic findings of AFX are discussed.

Ocular manifestations in the inherited DNA repair disorders

Deoxyribonucleic acid (DNA) repair is a fundamental process designed to keep the integrity of genomic DNA that is continuously challenged by intrinsic or environmental induced alterations. Numerous genes involved in DNA repair have been cloned and are involved in different DNA repair pathways: base excision repair, nucleotide excision repair, mismatch repair, DNA recombination. Inherited conditions due to mutations in DNA repair genes include mainly: xeroderma pigmentosum, Cockayne syndrome, Trichothiodystrophy, Bloom syndrome, Rothmund-Thomson syndrome, and Werner syndrome. Minor to major ocular manifestations occur in these syndromes. For example, eyelid skin cancers in xeroderma pigmentosum and retinal dystrophy in Cockayne syndrome are major features of these syndromes. This review focuses on the DNA repair pathways, the general and ocular features of the related syndromes, the laboratory tests useful for diagnosis, and the general processes implied with DNA repair (ultraviolet sensitivity, carcinogenesis, apoptosis, oxydative stress, and premature aging).

Germline and somatic mutations of the INK4a-ARF gene in a xeroderma pigmentosum group C patient

Xeroderma pigmentosum is an inheritable autosomal recessive DNA repair deficient syndrome characterized by a high predisposition to skin cancers. An elevated proportion of tumors from xeroderma pigmentosum patients harbor ultraviolet-induced mutations (CC:GG > TT:AA tandem transitions) of the p53 and/or the INK4a-ARF genes. Here, we report the clinical and molecular features of a 12 y old xeroderma pigmentosum patient who, in addition to severe cutaneous clinical symptoms, also had three unusual tumors, a mediastinal lymphoblastic lymphoma, an atypical fibroxanthoma, and an epithelioid hemangioma. Single strand conformation polymorphism and sequencing analysis of the p53 and INK4a-ARF genes were carried out in DNA from normal skin and different tumors (four actinic keratosis, two microinvasive squamous cell carcinomas, one basal cell carcinoma, and one atypical fibroxanthoma) from the patient. After characterization of the xeroderma pigmentosum C complementation group, we found unexpectedly that this patient also carried a germline mutation of the INK4a-ARF locus affecting the p16INK4A reading frame. Three different somatic mutations that all harbor the signature of ultraviolet light (two of p16INK4A and one of p53) were also detected in the basal cell carcinoma. We hypothesize that the germline mutation of p16INK4A, in association with the nucleotide excision repair defect, could explain the patient's unusual phenotype. Furthermore, this study confirms that concomitant somatic mutations of INK4a-ARF and p53 occur in some xeroderma pigmentosum associated tumors, and seem to accumulate during tumor progression rather than the initiation step.

Pediatric skin tumors

This article summarizes several malignant childhood neoplasms and benign tumors that can mimic malignancies. Because malignant skin tumors are rare in children, parents and physicians often are not sufficiently suspicious to ensure that an early diagnosis can be made. Many malignant skin tumors have features that suggest a vascular or hemangioma-like lesion. Because hemangiomas occur in 10% of infants, it is often considered prudent to adopt a wait-and-see attitude; however, if the lesion is too firm to be a hemangioma or its growth pattern does not follow that of a typical hemangioma, additional options should be considered. To manage childhood skin malignancies, one needs expert consultation, early biopsy, and correct histopathologic interpretation.

Xeroderma pigmentosum in Libya

BACKGROUND

A preliminary study of 24 cases of xeroderma pigmentosum (XP) was presented in 1990 and later published in 1992. Since then we have seen 18 further cases.

OBJECTIVE

To study the clinical profile of Libyan cases of XP.

METHODS

With the help of a special protocol, all 42 cases (23 girls and 19 boys from 29 families) treated and followed between 1981 and 1994 were subjected to detailed analysis.

RESULTS

A history of consanguinity was present in the parents of 39 patients. XP in Libya is characterized by a relatively high incidence (approximately 15-20 per million of the population), early onset of initial manifestations (median age, 12 months) and malignant tumors (median age, 8 years), severe ocular and oral lesions in a high percentage of patients, and early death (median age, 15.5 years). The malignant skin tumors seen were squamous cell carcinoma (SCC) in 23 patients, basal cell carcinoma (BCC) in 17 patients, and basosquamous carcinoma in two patients. Malignant melanoma was not seen, but lentigo maligna was found in one case. SCC of the tongue, carcinoma of the thyroid, and lymphatic leukemia affected individual patients. Subnormal physical growth was observed in six patients, but none of the patients had significant neurologic abnormalities. The results of etretinate therapy in nine patients revealed that it is an effective preventive agent against carcinogenesis, but not a curative one.

CONCLUSIONS

Severe ophthalmic manifestations affected a higher percentage of patients at an early age. Malignant melanoma did not develop in any case, except for lentigo maligna in one patient.

Detection of ultraviolet photoproducts in mouse skin exposed to natural sunlight

In the present study, we for the first time investigated the formation of ultraviolet (UV) photoproducts, cyclobutane pyrimidine dimers (CPDs), pyrimidine-pyrimidone (6-4) photoproducts (64PPs) and Dewar isomers, in vivo in shaved and depilated C3H/HeN mouse skin exposed to natural sunlight (NSL) at noon for 5 min to 1 h in mid-summer, using a highly sensitive immunohistochemical method. This method permits the quantitative analysis of UV-photoproducts in formalin-fixed, paraffinembedded sections with specific antibodies against CPDs, 64PPs and Dewar isomers. We demonstrated that the induction of CPDs in vivo in mouse skin by NSL was exposure time-dependent, but the accumulation of 64PPs or Dewar isomers was comparatively low in the skin sections from mice exposed to NSL in vivo. The results indicate that CPDs are the main photoproducts in vivo induced by sunlight and that their formation and repair may be important in connection with carcinogenesis in sun-exposed areas of human skin.

Environmental health science research and human risk assessment

Environmental health science research, with its focus on fundamental science and disease prevention, is important for the development of rational and cost-effective public health and regulatory policies related to environmental protection. Environmentally related diseases are preventable, yet they impose a major burden on society in terms of human suffering and costs related to health care. Similarly, the expenditure of hundreds of billions of dollars for regulatory compliance is a major economic concern. There is considerable debate regarding current regulatory risk assessment practices for environmental agents. Implicit in all risk assessment schemes is the need to extrapolate from high-exposure studies to low-exposure situations and from known risks in rodents to probable risks in people. Both extrapolations are fraught with uncertainties. These uncertainties are accommodated in risk-assessment schemes by the incorporation of arbitrary "safety factors" and other default approaches. Since these factors are not derived experimentally, they may overestimate or under estimate actual risks. Risk-assessment methodology, its relevance to the human condition, and its use in protecting human health will greatly improve when our expanding knowledge of the basic biology of environmental effects is incorporated into toxicological testing and risk-assessment schemes. Moreover, exciting opportunities now exist to advance our understanding of the environmental and genetic bases of many common diseases and to design effective prevention and intervention strategies to combat their development. This report discusses some of the current opportunities and challenges.

Expression of mitochondrial genes and DNA-repair-related nuclear genes is altered in xeroderma pigmentosum fibroblasts

Differential hybridization was used to detect repair defects in xeroderma pigmentosum (XP) that are not amenable to current analyses. cDNA libraries were constructed from cytoplasmic RNA of normal and XP fibroblast strains (complementation groups A and D) and analyzed for differential gene expression. More than 40,000 lambda gt10 cDNA clones were differentially screened with in vitro transcripts made from cDNA in the pBluescript vector. Six differential clones were detected in the libraries of the XP group A and D strains which caused stronger or weaker signals when probed with transcripts from XP strains than with those from the normal strains. Two clones coded for mitochondrial genes: mitochondrial 16 S rRNA and ATPase 6L. Overexpression of mitochondrial genes in XP may indicate that functions of the ATP-generating system are impaired since such functions are intensified whenever they become insufficient, for example as a consequence of DNA damage. It is tempting to assume that abnormal mitochondria are one of the causes for the neurological malfunctions in XP. Furthermore, densitometric analysis of Northern blots revealed that mRNA of lactate dehydrogenase, chain M, was less abundant in four XP group A strains (extent of reduction: 70%) and in two XP group D strains (extent of reduction: 58%). Enzyme activity was also diminished. In addition, mRNA of the gene for glyceraldehyde-3-phosphate dehydrogenase was less expressed in the same XP group A and D fibroblast strains investigated (reduction in both complementation groups: 50%). Both glycolytic enzymes have nuclear functions apart from their role in sugar metabolism. Lactate dehydrogenase, chain M, is identical to a helix-destabilizing protein; it is closely associated with chromatin and unfolded DNA, suggesting a role in DNA synthesis and transcription. The 37-kDa subunit of glyceraldehyde-3-phosphate dehydrogenase is involved in transcription and was shown to be identical to uracil-DNA glycosylase, a base-excision repair enzyme. We presume that the nuclear functions of these glycolytic enzymes may be thwarted in the XP strains investigated and may account for malfunctions in XP, particularly for neurological disturbances.

Oculocutaneous manifestations in xeroderma pigmentosa

Xeroderma pigmentosum (XP) is a rare genetic disease characterised by defective DNA repair leading to clinical and cellular hypersensitivity to ultraviolet radiation. The oculocutaneous features of 10 patients with XP were studied retrospectively. General features included parental consanguinity (40%), familiarity (60%), onset of symptoms in first 2 years (50%), malignant skin neoplasms (60%), and carcinoma of the tongue (20%). Among the ocular features, 50% of patients presented with photophobia. Lid freckles or atrophic skin lesions were seen in all patients. Lower lid tumours were seen in 30%, chronic conjunctival congestion in 40%, corneal opacification in 40%, squamous cell carcinoma of limbus in 20%, bilateral pterygium in 40%, and visual impairment in 50%. The clinical features (ocular and cutaneous) of the cases are discussed.

Induction and repair of UVB-induced cyclobutane pyrimidine dimers and (6-4) photoproducts in organ-cultured normal human skin

To examine the induction and repair of UV-induced DNA damage, indirect immunofluorescence was performed on UVB-irradiated organ-cultured normal human skin using monoclonal antibodies specific for either cyclobutane pyrimidine dimers or (6-4) photoproducts. Nuclear immunofluorescence of cyclobutane pyrimidine dimers and (6-4) photoproducts were observed in a dose-dependent manner after UVB irradiation. The intensity of nuclear immunofluorescence of the upper epidermal layers was stronger and clearer than that of the lower epidermal layers. DNA repair time-course studies showed that both types of DNA damage could be repaired within 24 h after UVB irradiation.

Co-recessive inheritance: A model for DNA repair and other surveillance genes in higher eukaryotes

The co-recessive inheritance hypothesis proposes that certain recessively inherited diseases require homozygosity and/or hemizygosity for defective alleles at more than one locus simultaneously for the trait to be expressed. Although this hypothesis was originally proposed in the context of defective alleles for genes coding for DNA-repair functions, it need not be limited to this context, and genetic selection pressure may favor this model for genes involved in surveillance of any type. The co-recessive inheritance hypothesis also predicts extremely high carrier frequencies, likely affecting much of the general population, for defective alleles associated with these rare recessive diseases. The model predicts much lower rates of consanguinity between the parents of affected individuals than autosomal recessive inheritance, allowing it to be tested epidemiologically, and recent data suggest that the hypothesis may be valid for some cases of ataxia telangiectasia and xeroderma pigmentosum. The model provides possible explanations for a number of otherwise puzzling findings in several diseases associated with defective DNA repair.

Xeroderma pigmentosum. A clinical study of 24 Libyan cases

BACKGROUND

Despite a high incidence of xeroderma pigmentosum, there is no previous publication from Libya.

OBJECTIVE

The purpose was to study the clinical profile of Libyan cases of xeroderma pigmentosum.

METHODS

With the help of a special protocol, 24 cases of xeroderma pigmentosum treated between 1981 and 1990 were subjected to detailed analysis.

RESULTS

The age of onset of initial manifestations ranged between 6 and 18 months whereas that of malignant lesions ranged from 2 to 10 years. Malignant lesions observed were squamous cell carcinoma in 15 patients, basal cell carcinoma in 12, and basosquamous carcinoma in 2 patients; squamous cell carcinoma of the tongue, carcinoma of the thyroid, and lymphatic leukemia affected individual cases. None of our patients developed malignant melanoma. Six patients have died; the age at death ranged between 9 and 18 years. A history of consanguinity in the parents of patients was recorded in all but two patients.

CONCLUSION

We observed early onset of severe ophthalmic lesions affecting a higher percentage of the patients.

Epibulbar squamous cell carcinomas in brothers with Xeroderma pigmentosa

We report two brothers aged 6.6 and 5 years old with the De Sanctis-Cacchione variant of Xeroderma Pigmentosa. They had typically severe skin, and ocular and neurologic involvement. Both had epibulbar squamous cell carcinomas. The oldest presented with a large, invasive, epibulbar mass of the left eye which required enucleation. He also had an invasive squamous cell carcinoma of the right lower lid. The younger brother presented with a smaller papillomatous lesion at the medial limbus of the right eye. After removal, this was found to be squamous cell carcinoma in-situ. Flow cytometry done on the tumors revealed diploidy. The case descriptions, histopathology, and discussion of ocular manifestations are presented.

Defects in antioxidant defense and calcium transport in the epidermis of xeroderma pigmentosum patients

A comparative study of the antioxidant enzymes superoxide dismutase, catalase, glutathione reductase and thioredoxin reductase was undertaken in two families with xeroderma pigmentosum (XP) and in healthy controls of corresponding skin phototypes. Epidermal blister roofs obtained from the XP patients revealed significant decreases in catalase, thioredoxin reductase, and superoxide dismutase, but glutathione reductase was unaffected. In addition, keratinocytes established from XP patients contained a significantly higher than normal intracellular calcium concentration compared with control cells from a corresponding skin type. Keratinocytes established from an XP obligate heterozygote revealed intermediate levels of calcium between XP homozygotes and controls. Previously high intracellular calcium has been shown to compromise the redox status of keratinocytes by allosteric inhibition of the thioredoxin reductase/thioredoxin electron transfer system. In XP homozygous keratinocytes from sun-exposed epidermis, the intracellular concentration of reduced thioredoxin was decreased to 50% compared with these cells from unexposed skin. Taken together, the results from this study indicate that the epidermis in XP patients lacks effective defense against free radicals and peroxides. In addition to the well-established defect in the normal rates of unscheduled DNA repair, these findings provide an even better explanation for the multiple cutaneous neoplasms in these patients.

Flowcytometric analysis of DNA pattern of cells derived from xeroderma pigmentosum A--hypersensitivity to vincristine, etoposide and methotrexate

Xeroderma pigmentosum complementation group A (XPA) is one of the DNA repair deficient syndromes. The cell biological features of XPA were examined by flowcytometry using Epstein Barr (EB) virus-transformed lymphoblastoid cells. Cellular sensitivity to vincristine (VCR), etoposide (VP-16) and methotrexate (MTX) were assayed by DNA pattern changes by flowcytometry. Recently, ataxia-telangiectasia (AT), one of the same kind of disorder, has been reported to have an increased sensitivity to VCR and VP-16. However, AT showed some resistance to MTX according to other reports. Our results showed that XPA had an increased sensitivity to VCR and also to VP-16. Moreover, different from AT, XPA showed some sensitivity to MTX. Thus there is some cell biological similarity between XPA and AT, as well as some difference of the abnormality in the DNA repair pathway.

Xeroderma pigmentosum variant: response to etretinate

We report a case of the variant form of xeroderma pigmentosum in whom tumour development was completely suppressed for 22 months by etretinate 25 mg daily.

Search for consanguinity within and among families of patients with trichothiodystrophy associated with xeroderma pigmentosum

The association of two rare hereditary disorders, trichothiodystrophy (TTD) and xeroderma pigmentosum (XP), was found in four patients from three families, apparently unrelated but living in the same geographical area. In order to test the hypothesis of a common ancestor, consanguinity within and among the families was checked using three different approaches: reconstruction of genealogical trees, typing of blood markers, and surname analysis. The results of the three types of analyses strengthen the hypothesis that, in at least two out of the three families, the genetic defect determining the TTD/XP phenotype is identical by descent, as a consequence of remote inbreeding. This implies that if two mutations are responsible for the two diseases they are at linked loci or affect the same gene.

Ultraviolet-induced chromosomal instability in cultured fibroblasts of heterozygote carriers for xeroderma pigmentosum

Fibroblast cultures of seven patients with xeroderma pigmentosum (XP), 19 healthy sibs or parents of XP patients (XP-heterozygotes), and 24 healthy normal controls were studied for chromosome instability induced by ultraviolet rays (UV). We used a UV source that contained predominantly UV-A and UV-B at an intensity of 500 J/m2 and evaluated the induction of micronuclei (MN) and sister chromatid exchange (SCE). the XP homozygotes had a UV sensitivity that was clearly above that of all heterozygotes and normal controls. Heterozygotes had an increased rate of UV-induced MN (4.76 +/- 1.96 vs. 1.82 +/- 2.05, p less than 0.0001) and increased UV induction of SCE (13.21 +/- 3.49 vs. 9.01 +/- 1.25, p less than 0.001), as compared to normal controls. These data support epidemiologic findings that suggest that XP heterozygotes are particularly cancer prone. In addition, the determination of the UV sensitivity in vitro as described may be used for genetic counseling of asymptomatic relatives of XP patients.