Clinical and photobiological characteristics of xeroderma pigmentosum complementation group F: a review of cases from Japan

Xeroderma Pigmentosum: General Aspects and Management

Xeroderma Pigmentosum (XP) is a rare genetic syndrome with a defective DNA nucleotide excision repair. It is characterized by (i) an extreme sensitivity to ultraviolet (UV)-induced damages in the skin and eyes; (ii) high risk to develop multiple skin tumours; and (iii) neurologic alterations in the most severe form. To date, the management of XP patients consists of (i) early diagnosis; (ii) a long-life protection from ultraviolet radiation, including avoidance of unnecessary UV exposure, wearing UV blocking clothing, and use of topical sunscreens; and (iii) surgical resections of skin cancers. No curative treatment is available at present. Thus, in the last decade, in order to prevent or delay the progression of the clinical signs of XP, numerous strategies have been proposed and tested, in some cases, with adverse effects. The present review provides an overview of the molecular mechanisms featuring the development of XP and highlights both advantages and disadvantages of the clinical approaches developed throughout the years. The intention of the authors is to sensitize scientists to the crucial aspects of the pathology that could be differently targeted. In this context, the exploration of the process underlining the conception of liposomal nanocarriers is reported to focus the attention on the potentialities of liposomal technology to optimize the administration of chemoprotective agents in XP patients.

Skin tumors in xeroderma pigmentosum: Evaluation of a large series and a literature review

BACKGROUND

Xeroderma pigmentosum (XP) is a rare genodermatosis with a lifelong propensity to develop malignant skin tumors.

METHODS

In this retrospective study, 24 XP patients were evaluated with regard to frequency and clinicopathological features of benign and malignant skin tumors.

RESULTS

Seventeen patients had at least one malignant skin tumor diagnosed: basal cell carcinoma (BCC) in 13 patients (n = 72), basosquamous carcinoma in three patients (n = 4), squamous cell carcinoma in six patients (n = 13), keratoacanthoma in three patients (n = 15), and melanoma in six patients (n = 18). Most melanomas (n = 15) were in situ lesions. Several benign skin tumors were noted such as tricholemmoma (n = 1), trichoepithelioma (n = 1), trichoblastoma (n = 1), follicular infundibulum tumor (n = 1), keratoacanthoma-like follicular lesion (n = 1), adnexal tumors with folliculosebaceous (n = 1) and tricholemmal differentiation (n = 1), and neurofibroma (n = 1). Benign vascular proliferations including pyogenic granulomas (n = 8), widespread telangiectasias, and senile angioma-like lesions were also observed in 3, 5, and 5 patients, respectively.

CONCLUSIONS

Similar to many reports, BCC was found to be the most common malignant skin tumor. The high prevalence of benign adnexal tumors of follicular differentiation, some of them showing mixed histopathological features and various vascular proliferations in our series raises the question of whether they indicate a formerly undescribed association with XP.

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.

SLX4IP acts with SLX4 and XPF-ERCC1 to promote interstrand crosslink repair

Interstrand crosslinks (ICLs) are highly toxic DNA lesions that are repaired via a complex process requiring the coordination of several DNA repair pathways. Defects in ICL repair result in Fanconi anemia, which is characterized by bone marrow failure, developmental abnormalities, and a high incidence of malignancies. SLX4, also known as FANCP, acts as a scaffold protein and coordinates multiple endonucleases that unhook ICLs, resolve homologous recombination intermediates, and perhaps remove unhooked ICLs. In this study, we explored the role of SLX4IP, a constitutive factor in the SLX4 complex, in ICL repair. We found that SLX4IP is a novel regulatory factor; its depletion sensitized cells to treatment with ICL-inducing agents and led to accumulation of cells in the G2/M phase. We further discovered that SLX4IP binds to SLX4 and XPF-ERCC1 simultaneously and that disruption of one interaction also disrupts the other. The binding of SLX4IP to both SLX4 and XPF-ERCC1 not only is vital for maintaining the stability of SLX4IP protein, but also promotes the interaction between SLX4 and XPF-ERCC1, especially after DNA damage. Collectively, these results demonstrate a new regulatory role for SLX4IP in maintaining an efficient SLX4-XPF-ERCC1 complex in ICL repair.

Xeroderma pigmentosum complementation group F: A rare cause of cerebellar ataxia with chorea

The complementation group F of Xeroderma pigmentosum (XP-F) is rare in the Caucasian population, and usually devoid of neurological symptoms. We report two cases, both Caucasian, who exhibited progressive cerebellar ataxia, chorea, a mild subcortical frontal cognitive impairment, and in one case severe polyneuropathy. Brain MRI demonstrated cerebellar (2/2) and cortical (1/2) atrophy. Both patients had only mild sunburn sensitivity and no skin cancer. Mini-exome sequencing approach revealed in ERCC4, two heterozygous mutations, one of which was never described (c.580-584+1delCCAAGG, exon 3), in the first case, and an already reported homozygous mutation, in the second case. These cases emphasize that XP-F is a rare cause of recessive cerebellar ataxia and can in some cases clinically mimic Huntington's disease due to chorea and executive impairment. The association of ataxia, chorea, and sun hypersensitivity are major guidance for the diagnosis, which should not be missed, in order to prevent skin neoplastic complications.

Genomic variation in seven Khoe-San groups reveals adaptation and complex African history

The history of click-speaking Khoe-San, and African populations in general, remains poorly understood. We genotyped ~2.3 million single-nucleotide polymorphisms in 220 southern Africans and found that the Khoe-San diverged from other populations ≥100,000 years ago, but population structure within the Khoe-San dated back to about 35,000 years ago. Genetic variation in various sub-Saharan populations did not localize the origin of modern humans to a single geographic region within Africa; instead, it indicated a history of admixture and stratification. We found evidence of adaptation targeting muscle function and immune response; potential adaptive introgression of protection from ultraviolet light; and selection predating modern human diversification, involving skeletal and neurological development. These new findings illustrate the importance of African genomic diversity in understanding human evolutionary history.

The cerebro-morphological fingerprint of a progeroid syndrome: white matter changes correlate with neurological symptoms in xeroderma pigmentosum

Background

Xeroderma pigmentosum (XP) is a rare autosomal recessive progeroid syndrome. It has recently been shown that the underlying DNA repair defect plays a central role in the aging process. In addition to skin symptoms, various premature neurological abnormalities have been reported.

Methodology/Principal Findings

We present the clinical neurological phenotype in 14 XP patients (seven subtypes), in seven of these patients together with conventional and multiparametric advanced MRI data to assess the macrostructural and microstructural cerebral morphology in comparison to controls, including volumetric measurements, MR spectroscopy (¹H MRS), and diffusion tensor imaging (DTI). Clinical hallmarks were spinocerebellar ataxia, pyramidal tract signs, and mild cognitive deficits. DTI demonstrated significantly reduced WM directionality in all regions investigated, i.e. the thalamus, the corticospinal tracts and the dorsal corpus callosum. Single patients showed a marked relative hippocampal volume reduction, but the patients were not different from controls in the volumetric measurements of hippocampal and whole brain volumes at group level. However, ¹H MRS demonstrated that the hippocampal formation was metabolically altered.

Conclusions

The most prominent feature was the white matter affectation, as assessed by DTI, with volume and directionality reductions of the fiber projections involving both the craniocaudal fibers and the interhemispheric connections. These findings, although heterogeneous among the study sample, could be correlated with the clinico-neurological symptoms. The imaging findings support the position that myelin structures degrade prematurely in the brain of XP patients.

Physiological consequences of defects in ERCC1-XPF DNA repair endonuclease

ERCC1-XPF is a structure-specific endonuclease required for nucleotide excision repair, interstrand crosslink repair, and the repair of some double-strand breaks. Mutations in ERCC1 or XPF cause xeroderma pigmentosum, XFE progeroid syndrome or cerebro-oculo-facio-skeletal syndrome, characterized by increased risk of cancer, accelerated aging and severe developmental abnormalities, respectively. This review provides a comprehensive overview of the health impact of ERCC1-XPF deficiency, based on these rare diseases and mouse models of them. This offers an understanding of the tremendous health impact of DNA damage derived from environmental and endogenous sources.

XPF/ERCC4 and ERCC1: their products and biological roles

ERCC4 is the gene mutated in XPF cells and also in rodent cells representing the mutant complementation groups ERCC4 and ERCC 11. The protein functions principally as a complex with ERCC1 in a diversity of biological pathways that include NER, ICL repair, telomere maintenance and immunoglobulin switching. Sorting out these roles is an exciting and challenging problem and many important questions remain to be answered. The ERCC1/ERCC4 complex is conserved across most species presenting an opportunity to examine some functions in model organisms where mutants can be more readily generated and phenotypes more quickly assessed.

Xeroderma pigmentosum: a retrospective case series in Zimbabwe

PURPOSE

To present our experience with the clinical features and management of black African patients with xeroderma pigmentosum (XP).

PATIENTS AND METHODS

Twelve patients with XP were seen over a 25-year period, and were retrospectively reviewed for age, gender, clinical features, treatment, and follow-up.

RESULTS

There were 8 females and 4 males with an age range of 3 to 18 years. One patient, the longest survivor, was followed until death at 18 years. Nine patients had the severe form of XP and 3 had the mild form. All patients had early ocular involvement with photophobia and early blindness. Squamous cell carcinoma (SCC) was present on the skin, lip, and tongue in most patients. One patient had ocular surface SCC. There was marked skin photosensitivity. No history of consanguinity was noted in the parents of the patients. Surgery was the treatment modality of choice. Follow-up was poor.

CONCLUSION

XP is uncommon in our black population, and presents in the severe form with SCC as the malignant skin, lip, and tongue lesion. It is common in early childhood with severe photosensitivity, photophobia, and eventual blindness. Follow-up is difficult in our environment.

Partial complementation of the DNA repair defects in cells from xeroderma pigmentosum groups A, C, D and F but not G by the denV gene from bacteriophage T4

Endonuclease V (denV) from bacteriophage T4 was examined for its ability to complement the DNA repair defect in xeroderma pigmentosum (XP) cells from complementation groups A, C, D, F and G. The denV gene was introduced into SV40-transformed normal and XP cells using a retroviral vector. Expression of denV resulted in partial correction of UV sensitivity and increased host cell reactivation (HCR) of a UV-damaged reporter gene for XP cells from groups A, C and D, but not those from group G. Expression of denV in XP-F cells resulted in enhanced HCR of a UV-damaged reporter but did not affect UV sensitivity. The observed partial complementation is thought to reflect denV-mediated repair of cyclobutane-pyrimidine dimers (CPD), and is incomplete as denV does not recognize other UV-induced lesions, and may not even efficiently remove all CPD. As XP-F cells are believed to retain near-normal levels of CPD repair in the bulk of the genome, we believe that the disparity in the ability of denV to complement the repair deficiency in these cells results from an increased rate, but not level, of CPD repair. Furthermore, we suggest that the lack of correction in the XP-G cells examined results from an inability to process denV-incised CPD by the base excision repair pathway, as has been suggested for cells from the related genetic disorder, Cockayne syndrome. Expression of denV in repair proficient normal cells also resulted in increased HCR of the UV-damaged reporter construct, possibly arising from an increased rate of CPD repair in these cells.

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.

Familial hydroa vacciniforme

Hydroa vacciniforme is a rare, idiopathic photodermatosis with an onset in childhood and characterized by acute vesiculation, crusting and scarring following sun exposure. Familial cases are extremely rare with only one previous report. We report a brother and sister, both of whom have developed hydroa vacciniforme.

Homozygous R788W point mutation in the XPF gene of a patient with xeroderma pigmentosum and late-onset neurologic disease

The second Caucasian xeroderma pigmentosum patient (XP42RO) belonging to complementation group F (XP-F) is described. Mild ocular photophobia was present from childhood, and acute skin reactions occurred upon exposure to sunlight. Basal and squamous cell carcinomas developed after his twenty-seventh year. In his late forties progressive neurologic symptoms emerged, which included intellectual decline, mild chorea and ataxia, and marked cerebral and cerebellar atrophy. Such neurologic abnormalities are very unusual in XP-F. Similar symptoms have been described in only one of 17 other XP-F individuals. His approximately 5-fold reduced activity of nucleotide excision repair in cultured cells, combined with moderately affected cell survival and DNA replication after UV exposure, are typical of XP-F. The recent cloning of the XPF gene allowed a molecular genetic analysis of this unusual patient. XP42RO, representing the second case studied in this respect, turned out to be homozygous for a point mutation in the XPF gene, causing an R788-->W substitution in the encoded protein. Surprisingly, this mutation had also been found in one allele of the other unrelated Caucasian XP-F case. The amount of mutated XPF protein is strongly reduced in cells from XP42RO, presumably due to a conformational change. Biochemical, genetic, and clinical data all indicate the presence of considerable residual repair activity, strongly suggesting that the R788W mutation is leaky.

Xeroderma pigmentosum group F caused by a defect in a structure-specific DNA repair endonuclease

Nucleotide excision repair, which is defective in xeroderma pigmentosum (XP), involves incision of a DNA strand on each side of a lesion. We isolated a human gene homologous to yeast Rad1 and found that it corrects the repair defects of XP group F as well as rodent groups 4 and 11. Causative mutations and strongly reduced levels of encoded protein were identified in XP-F patients. The XPF protein was purified from mammalian cells in a tight complex with ERCC1. This complex is a structure-specific endonuclease responsible for the 5' incision during repair. These results demonstrate that the XPF, ERCC4, and ERCC11 genes are equivalent, complete the isolation of the XP genes that form the core nucleotide excision repair system, and solve the catalytic function of the XPF-containing complex.

Neurocutaneous syndromes associated with pigmentary skin lesions

Tremendous strides have been made in our understanding of genetic disorders, including those that involve both the skin and the nervous system. The list of well-established neurocutaneous syndromes has increased during a few decades from a few classical phakomatoses to more than 30 entities. The dermatologist has the opportunity to facilitate precise diagnosis and optimal care for these patients by recognition of the cutaneous markers for these diseases. We have attempted to provide an overview of some recent advances in those syndromes manifested by pigmentary skin changes, emphasizing the clinical spectrum of each disorder and providing guidelines for an approach to management.

A young woman with xeroderma pigmentosum complementation group F and a morphoeic basal cell carcinoma

We report an 18-year-old Japanese woman who had mild photosensitivity and a facial tumour, which was shown to be a morphoeic basal cell carcinoma. Although a line of fibroblasts derived from the patient, Kps6 cells, were slightly more sensitive to UV irradiation than normal cells, their level of unscheduled DNA synthesis was about 20% that of normal cells, and recovery of RNA synthesis after UV irradiation was moderately depressed. Complementation tests, carried out by cell fusion or by microinjection of plasmids harbouring xeroderma pigmentosum (XP) genes, indicated that the patient had XP group F. To our knowledge, this is the youngest XP group F patient with a malignant tumour reported to date.

UV-induced base substitution mutations in a shuttle vector plasmid propagated in group C xeroderma pigmentosum cells

To assess the contribution to mutagenesis of human DNA repair defects, the UV-irradiated shuttle vector plasmid pZ189 was propagated in fibroblasts derived from a xeroderma pigmentosum (XP) patient in DNA repair complementation group C. In comparison to results with DNA repair-proficient human cells (WI-38 VA13), UV-irradiated pZ189 propagated in the XP-C (XP4PA(SV)) cells showed fewer surviving plasmids and a higher frequency of mutated plasmids. Base sequence analysis of 67 mutated plasmids recovered from the XP-C cells revealed similar classes of point mutations and mutation spectrum, and a higher frequency of G:C to A:T transitions along with a lower frequency of transversions among plasmids with single or tandem mutations compared to plasmids recovered from the normal line. Most single-base substitution mutations (83%) occurred at G:C base pairs in which the 5'-adjacent base of the cytosine was thymine or cytosine. These results indicate that the DNA repair defects in XP-C, in comparison to data previously reported for XP-A, XP-D and XP-F, result in different UV survival and mutation frequency but in similar types of base substitution mutations.

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.