The gene for incontinentia pigmenti is assigned to Xq28

MACULAR NEUROVASCULAR ABNORMALITIES IN A CHILD WITH INCONTINENTIA PIGMENTI ON HANDHELD OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY

PURPOSE

To report macular neurovascular abnormalities in a child with incontinentia pigmenti using handheld optical coherence tomography (OCT) and OCT angiography (OCT-A).

METHODS

An eye of a child with incontinentia pigmenti enrolled in BabySTEPS was imaged using an investigational noncontact, handheld swept-source OCT device during examination under anesthesia. Custom MATLAB scripts were used to generate depth-resolved vascular slabs, B-scans with flow overlay, and retinal thickness maps.

RESULTS

Depth-resolved OCT and OCT-A imaging demonstrated focal areas of decreased capillary flow that corresponded to areas of both inner retinal and outer retinal thinning on retinal thickness maps. Atypical diving of superficial retinal vessels occurred as they traversed from thin retina to normal-thickness retina.

CONCLUSION

Depth-resolved OCT and OCT-A identified retinal vascular abnormalities that were not evident on fundus photography or fluorescein angiography. This case depicted concurrent, localized abnormalities in retinal thickness and microvasculature in an eye with incontinentia pigmenti.

A Turkish case of incontinentia pigmenti with a deletion mutation at Inhibitor of kappa B kinase gamma gene

Background

Incontinentia pigmenti (IP) is a rare X-linked dominant disorder affecting the skin and other ectodermal tissues that is caused by a mutation of the IKBKG/NEMO gene.

Case presentation

We describe a Turkish family with IP. Sanger sequencing was performed in our patient with IP, and we identified DNA variant c.172_173delAA (p.Asn58SerfsTer79) in IKBKG. We found the same mutation in the patient's mother and grandmother.

Conclusion

Our report expands the mutation spectrum in this disorder and provides valuable information on the importance of the IKBKG. Our study shows that confirmation of the mutation analysis of IP in the suspected cases is necessary for future planning pregnancies.

Child with a mild phenotype of Incontinentia Pigmenti and inner retinal dysfunction

PURPOSE

To describe a case of a child with mild phenotype of Incontinentia Pigmenti (IP), with changes in Spectral-Domain Optical Coherence Tomography (SD-OCT) and Optical Coherence Tomography Angiography (OCT-A) and an electronegative dark-adapted (DA) 3.0 electroretinogram (ERG), suggestive of inner retinal dysfunction.

CASE REPORT

We described a 7-year-old female child with IP. Her best corrected acuity was 8/10 in the right eye and 6/10 in the left eye. Biomicroscopy, intraocular pressure and fundoscopy were normal. The electroretinography findings showed an electronegative DA 3.0 ERG with a normal a-wave but a b-wave that did not elevate above baseline. SD-OCT identified irregularities in the outer plexiform layer in both eyes, and OCT-A assessment revealed at the superficial capillary plexus, areas of decrease in the flow in parafoveal and perifoveal regions.

CONCLUSION

Classically, IP affects the peripheral retina; however, vascular and structural changes in macula can occur as well. To our knowledge, we report the first electronegative electroretinogram in a patient with IP.

Multimodal Retinal Imaging in Incontinentia Pigmenti Including Optical Coherence Tomography Angiography: Findings From an Older Cohort With Mild Phenotype

Importance

Incontinentia pigmenti (IP) is a rare, X-linked dominant disease with potentially severe ocular complications that predominantly affect the peripheral retina. However, little is known about its effects on the macula.

Objective

To describe the structural and vascular abnormalities observed in the maculas of patients with IP and to correlate these findings with peripheral pathologies.

Design, Setting, and Participants

Prospective, cross-sectional study at Wilmer Eye Institute, Johns Hopkins University. Five participants with a clinical diagnosis of IP were included and underwent multimodal imaging with ultra-wide-field fluorescein angiography (FA), spectral-domain optical coherence tomography (OCT), and OCT angiography.

Main Outcomes and Measures

The structural and vascular abnormalities observed on spectral-domain OCT and OCT angiography and their correlation with peripheral pathologies seen on ultra-wide-field FA.

Results

A total of 9 eyes from 5 patients (median age, 20.5 years; range, 8.4-54.2 years) were included. Median Snellen visual acuity was 20/32 (range, 20/16 to 20/63). ultra-wide-field FA-identified retinal vascular abnormalities in all 7 eyes in which FA was obtained. These abnormalities included microaneurysms, areas of nonperfusion, and vascular anastomoses, most of which were peripheral to the standard view of 30° FA with peripheral sweeps. Structural abnormalities were observed in 6 eyes on spectral-domain OCT, including inner retinal thinning and irregularities in the outer plexiform layer. Optical coherence tomography angiography abnormalities were noted in all 9 eyes, including decreased vascular density, abnormal vascular loops, and flow loss in the superficial and deep plexuses, which corresponded to areas of retinal thinning on spectral-domain OCT.

Conclusions and Relevance

Although our study is limited by the small sample size, the findings suggest that multimodal imaging is useful for detecting structural and vascular abnormalities that may not be apparent on ophthalmoscopy in patients with IP. Macular pathologies, especially a decrease in vascular density on OCT angiography, are common. Further studies are needed to characterize further the association between macular and peripheral abnormalities in patients with IP.

VARIABLE EXPRESSION OF RETINOPATHY IN A PEDIGREE OF PATIENTS WITH INCONTINENTIA PIGMENTI

PURPOSE

To characterize the varied ocular manifestations of incontinentia pigmenti (IP) in a large pedigree.

METHODS

All available members of the kindred who were affected with IP were examined with ophthalmoscopy, wide-field color photos, and fluorescein angiography.

RESULTS

Individual family members demonstrated variable expression of retinopathy characteristic of IP. There was severe retinopathy in two eyes: one associated with concurrent persistent fetal vasculature and another with rhegmatogenous retinal detachment. Another individual with biopsy-confirmed IP demonstrated no retinopathy in either eye. When present, retinopathy manifested asymmetrically between eyes of the same individual.

CONCLUSION

Cutaneous manifestations of IP are irregular and nonuniform due to lyonization of the X chromosome. In this report, we identify asymmetric retinal disease between eyes in the same individual and variable retinal findings within the kindred. These differences may be explained by random inactivation of the X chromosome or other epigenetic modifications.

The results of early physiotherapy on a child with incontinentia pigmenti with encephalocele

This study aimed to exhibit the effects of early physiotherapy and discusses post-treatment results on a patient with incontinentia pigmenti (IP) with encephalocele. Physiotherapy evaluations of the child included cognitive, fine and gross motor development assessed with the Bayley Scales of Infant and Toddler Development - Third Edition (Bayley-III), disability level with the gross motor function classification system, gross motor function with the gross motor function measurement (GMFM), and tonus evaluation with the Modified Ashworth Scale. The child was included in a physiotherapy and rehabilitation programme based on neurodevelopmental treatment three times a week. Although cognitive and motor development according to Bayley-III improved in the present case, motor and cognitive retardation became more apparent with growth. GMFM results indicated a large improvement from 5.88% to 47.73%. Presentation of this case shows the significance of early physiotherapy in this first study on physiotherapy for IP during the early rehabilitation process.

Incontinentia pigmenti in boys: a series and review of the literature

Incontinentia pigmenti is a rare X-linked genodermatosis, often associated with male lethality in utero. Occurrences of this disease in boys have been reported, however, its clinical phenotype has not been well characterized. The purpose of this study was to report on additional instances of incontinentia pigmenti in boys and to review the clinical, laboratory, and molecular characteristics of all published such patients. A retrospective chart review and Medline search using the keywords incontinentia pigmenti, males, and NEMO gene was undertaken. Six new boys with incontinentia pigmenti were found in our database and 36 more were previously reported in the literature. The vesiculo-bullous stage was the most frequent clinical presentation at diagnosis (80%). Fifteen percent of patients had an initial unilateral presentation. Recurrences of this stage were noted in 16%. Stages 2 and 3 of the disease were present in only 72.5% and 75% of patients, respectively. Only 15% of the boys had a documented stage 4. Extracutaneous manifestations were also documented (30% - central nervous system manifestations, 35% - eye involvement, 30% - alopecia, 40% - teeth anomalies). Thirty two percent of boys had peripheral eosinophilia. Only five had evidence of NEMO gene mutation. The male phenotype has clinical features similar to those of the female phenotype. Unilateral presentation is a distinct occurrence in boys, especially in early stages. Anomalies are the most common extracutaneous findings, followed by eye, hair, and central nervous system abnormalities.

Clinical features of incontinentia pigmenti with emphasis on oral and dental abnormalities

One of interesting aspects in dermatology is the fact that skin may reflect the presence of anomalies in other organs and tissues. One such example is incontinentia pigmenti (IP), a rare, complex, X-linked genodermatosis. Clinical manifestations of IP according to evolution and prognosis can be considered as skin, as well as dental, eye, and central nervous system, changes. We have investigated a total of nine families with 25 subjects, 23 females and 2 males. In 12 female and 2 male subjects, all of them with clinical characteristics of IP, we observed the following abnormalities: teeth-shape anomalies (coni- or peg-like teeth), the presence of numerous cariotic teeth, early dental loss, delayed eruption, partial anodontia, and gothic palate. To our knowledge, this is the first time that the presence of gothic palate in patients with IP has been documented. As we found out, in two female subjects and one male subject, in which nonrandomed X inactivation did not occur, gothic palate could be supposed as characteristic of IP.

NEMO, NFkappaB signaling and incontinentia pigmenti

The identification of mutations in the NEMO gene in humans with incontinentia pigmenti and several other genetic conditions has led to an appreciation of the multiple roles of signaling through the NFkappaB pathway, and how erroneous signalling contributes to disease. The finding that the disease results from a common, recurrent mutation was surprising given the high variability in patients' phenotypes and illustrates the role of X inactivation and selection in females. Recent advances in mouse models and in understanding the multiple roles of NEMO in the cell provide additional avenues to define the various roles of NEMO in NFkappaB signaling.

[Pustular diseases of the newborn]

In the newborn, there exists a wide spectrum of pustular skin diseases. These range from transitory, benign adaptation disorders up to systemic, life threatening illnesses. In 30-60% of newborns pustules are observed in association with the relatively harmless Erythema toxicum, the origin of which is still unknown today. It is necessary to differentiate this from the pustular diseases which may be of infectious or non-infectious nature and which require therapy. Typical pathogens include Malassezia furfur, Staphylococci, Streptococci, Candida spp. and the herpes virus group.

Unusual neonatal presentation of incontinentia pigmenti with persistent pulmonary hypertension of the newborn: a case report

Incontinentia pigmenti (Bloch-Sulzberger syndrome) is a multisystem disorder with classical changing skin lesions. The other systems that are involved include the central nervous system, eye, hair, teeth, musculoskeletal system and, occasionally, the cardiovascular system. We report a neonate with a diagnosis of incontinentia pigmenti who presented at birth with pulmonary hypertension. This presentation has not been described in the literature.

Incontinentia pigmenti: a window to the role of NF-kappaB function

Incontinentia pigmenti is an uncommon X-linked dominant genodermatosis primarily affecting females. Its hallmark is a unique skin eruption that presents in infancy along the lines of Blaschko and evolves through four stages: inflammatory, verrucous, hyperpigmented, and atrophic. Other persistent findings of the disease include alopecia and dental anomalies. In a minority of cases, serious ophthalmologic and neurological alterations may occur. Mutations in the NF-kappaB essential modulator (NEMO) that lead to an inability to activate the NF-kappaB pathway produce IP. Less deleterious mutations in NF-kappaB essential modulator give rise to hypohidrotic ectodermal dysplasia with immune deficiency in affected males, a related but distinct phenotype. These recent discoveries provide insight into the crucial role of NF-kappaB function in regulating the developmental, inflammatory, immune, and anti-apoptotic responses of the skin and other organs.

Incontinentia pigmenti: a review and update on the molecular basis of pathophysiology

Incontinentia pigmenti is an uncommon X-linked dominant disorder, lethal in the majority of affected males in utero and variably expressed in females. Cutaneous manifestations are classically subdivided into 4 stages: vesicular, verrucous, hyperpigmented, and atrophic. Various hair and nail abnormalities, dental anomalies, and ophthalmologic and neurologic deficits are associated with the disorder. The gene for incontinentia pigmenti has been mapped to Xq28. Recently, mutations in the NEMO/IKKgamma gene located at Xq28 have been found to cause expression of the disease. Knockout mice heterozygous for NEMO/IKKgamma gene deficiency develop a clinical phenotype very similar to that of incontinentia pigmenti. NEMO/IKKgamma is an essential component of the newly discovered nuclear factor kappaB (NF-kappaB) signaling pathway. When activated, NF-kappaB controls the expression of multiple genes, including cytokines and chemokines, and protects cells against apoptosis. The mechanism by which NEMO/IKKgamma deficiency causes, via the NF-kappaB pathway, the phenotypical expression of the disease has recently been elucidated. In addition, the newest research findings on eosinophil recruitment through eotaxin release by activated keratinocytes are described in the review. Finally, anhidrotic ectodermal dysplasia with immunodeficiency, a disorder allelic to incontinentia pigmenti, is discussed together with implications on the current understanding of NF-kappaB function. (J Am Acad Dermatol 2002;47:169-87.)

LEARNING OBJECTIVE

At the completion of this learning activity, participants will have a comprehensive and current understanding of incontinentia pigmenti, including its typical and uncommon clinical and histopathologic characteristics, diagnostic assessment, and current management strategies. Additionally, participants will gain the most current knowledge of the genetic and molecular basis of cutaneous pathomechanism.

Management of incontinentia pigmenti: a case of monolateral preretinal fibrovascular proliferations adjacent to snail-track degeneration areas

PURPOSE

To report a case of monolateral preretinal fibrovascularproliferations in a young adult woman, who had suffered from incontinentia pigmenti (IP) during her first month of life.

METHODS

Case report.

RESULTS

Circumscribed preretinal fibrovascular proliferations, adjacent to a mid-peripheral area of snail track degeneration, were occasionally diagnosed in the left eye of an asymptomatic 18-year-old white female. Careful ocular examination did not reveal any cause of the monolateral vascular abnormalities observed in the posterior segment. A detailed medical history brought to light that the patient has suffered infantile IP, like four other females in her family. The patient did not present any evident malformation of teeth, nails, skeleton or hair. A cytogenetic linkage study documented a chromosomal aberration in the Xq28 band, which confirmed the diagnosis of familial IP (type 2). The fluorescein angiography findings clearly illustrated the minimal retinal involvement in the course of IP.

CONCLUSIONS

This case shows that a wide range of etiologies must be considered in patients presenting monolateral preretinal fibrovascular proliferations. To correctly manage these uncommon, inherited or acquired, retinal diseases it is better to do a mid-term follow-up, rather than operate immediately, and this enabled us to observe the natural course of the lesion, while awaiting a definitive diagnosis.

Expression of eotaxin, an eosinophil-selective chemokine, parallels eosinophil accumulation in the vesiculobullous stage of incontinentia pigmenti

Incontinentia pigmenti (IP) is an X-linked dominant genodermatosis primarily affecting female children. The initial vesiculobullous stage of IP is characterized clinically by inflammatory papules, blisters, and pustules, and histopathologically by acanthosis, keratinocyte necrosis, epidermal spongiosis and massive epidermal eosinophil infiltration. The cause of this multisystem disease is attributed to the mutations of an X-linked regulatory gene, termed nuclear factor-kappaB essential modulator (NEMO). The exact mechanism of epidermal eosinophil accumulation has not yet been determined. We explored the possible role of an eosinophil-selective, nuclear factor-kappaB-activated chemokine, eotaxin, in the accumulation of eosinophils in the initial stage of the disease. Monoclonal antibody (6H9) specific for human eotaxin strongly labelled the suprabasal epidermis of IP skin, paralleling the upper epidermal accumulation of eosinophils, but did not label the epidermis of normal skin or lesional skin from patients with other inflammatory skin diseases not characterized by prominent eosinophil accumulation, namely dermatitis herpetiformis and selected cases of atopic dermatitis lacking significant numbers of eosinophils. In addition, endothelial cells in lesional skin of IP also exhibited strong expression of eotaxin, which correlated with perivascular and intravascular eosinophil infiltration. We also examined the in vitro effects on epidermally derived eotaxin of several cytokines that were nuclear factor-kappaB-activated and/or known to induce eotaxin expression. In normal human keratinocytes, proinflammatory cytokines either independently (IL-1alpha) or synergistically (tumour necrosis factor-alpha (TNF-alpha)/ interferon-gamma (IFN-gamma) and TNF-alpha/IL-4) up-regulated eotaxin expression. These studies suggest that release of cytokines during the initial inflammatory stage of IP induces epidermal expression of eotaxin, which may play a role in the epidermal accumulation of eosinophils.

Physical and genetic characterization reveals a pseudogene, an evolutionary junction, and unstable loci in distal Xq28

A large portion of human Xq28 has been completely characterized but the interval between G6PD and Xqter has remained poorly understood. Because of a lack of stable, high-density clone coverage in this region, we constructed a 1.6-Mb bacterial and P1 artificial chromosome (BAC and PAC, respectively) contig to expedite mapping, structural and evolutionary analysis, and sequencing. The contig helped to reposition previously mismapped genes and to characterize the XAP135 pseudogene near the int22h-2 repeat. BAC clones containing the distal int22h repeats also demonstrated spontaneous rearrangements and sparse coverage, which suggested that they were unstable. Because the int22h repeats are involved in genetic diseases, we examined them in great apes to see if they have always been unstable. Differences in copy number among the apes, due to duplications and deletions, indicated that they have been unstable throughout their evolution. Taking another approach toward understanding the genomic nature of distal Xq28, we examined the homologous mouse region and found an evolutionary junction near the distal int22h loci that separated the human distal Xq28 region into two segments on the mouse X chromosome. Finally, haplotype analysis showed that a segment within Xq28 has resisted excessive interchromosomal exchange through great ape evolution, potentially accounting for the linkage disequilibrium recently reported in this region. Collectively, these data highlight some interesting features of the genomic sequence in Xq28 and will be useful for positional cloning efforts, mouse mutagenesis studies, and further evolutionary analyses.

A pregnancy following PGD for X-linked dominant [correction of X-linked autosomal dominant] incontinentia pigmenti (Bloch-Sulzberger syndrome): case report

Incontinentia Pigmenti (Bloch-Sulzberger syndrome) is a rare multisystem, ectodermal disorder associated with dermatological, dental and ocular features, and in <10% of cases, severe neurological deficit. Pedigree review suggests X-linked dominance with lethality in affected males. Presentation in female carriers is variable. Following genetic counselling, a mildly affected female carrier diagnosed in infancy with a de novo mutation was referred for preimplantation sexing, unusually selecting for male gender, with an acceptance of either normality or early miscarriage in an affected male. Following standard in-vitro fertilization and embryo biopsy, fluorescence in situ hybridization (FISH) unambiguously identified two male and two female embryos. A single 8-cell, grade 4 male embryo was replaced. A positive pregnancy test was reported 2 weeks after embryo transfer, although ultrasonography failed to demonstrate a viable pregnancy. Post abortive fetal tissue karyotyping diagnosed a male fetus with trisomy 16. This is an unusual report of preimplantation genetic diagnosis (PGD) being used for selection of males in an X-linked autosomal dominant disorder and demonstrates the value of PGD where amniocentesis or chorion villus sampling followed by abortion is not acceptable to the patient. This case also demonstrates the importance of follow-up prenatal diagnosis.

Dermatologic clues to inherited disease

Genetic diseases often have cutaneous manifestations, which can be the first or most prominent signs of the underlying problem. Recognition of these dermatologic clues allows prompt diagnosis and intervention. In this article, the authors have attempted to outline several important examples of genodermatoses.

Female mice heterozygous for IKK gamma/NEMO deficiencies develop a dermatopathy similar to the human X-linked disorder incontinentia pigmenti

IKK gamma/NEMO is the essential regulatory subunit of the I kappa B kinase (IKK), encoded by an X-linked gene in mice and humans. It is required for NF-kappa B activation and resistance to TNF-induced apoptosis. Female mice heterozygous for Ikk gamma/Nemo deficiency develop a unique dermatopathy characterized by keratinocyte hyperproliferation, skin inflammation, hyperkeratosis, and increased apoptosis. Although Ikk gamma+/- females eventually recover, Ikk gamma- males die in utero. These symptoms and inheritance pattern are very similar to those of incontinentia pigmenti (IP), a human genodermatosis, synthenic with the IKK gamma/NEMO locus. Indeed, biopsies and cells from IP patients exhibit defective IKK gamma/NEMO expression but normal expression of IKK catalytic subunits. This unique self-limiting disease, the first to be genetically linked to the IKK signaling pathway, is dependent on X-chromosome inactivation. We propose that the IKK gamma/NEMO-deficient cells trigger an inflammatory reaction that eventually leads to their death.

Hypomelanosis of ito and a 'mirror image' whole chromosome duplication resulting in trisomy 14 mosaicism

We describe a female infant with multiple congenital anomalies including unusual hyperpigmentation, tetralogy of Fallot, absent corpus callosum and wide prominent nasal bridge. The infant was initially seen for genetic consultation on day one after birth. Chromosome analysis from cultured lymphocytes showed a normal 46,XX karyotype. However, cultured skin fibroblasts showed mosaicism with 46,XX,add(14)(q32).ish psu dic dup(14)(q32p13)(wcp14+)/46,XX complements. A review of the published report with chromosome mosaicism and hypomelanosis of Ito (HMI) is included. We suggest that the trisomy 14 mosaicism seen in fibroblast cultures has importance in the expression of pigmentation dysplasias in this patient. Pigmentary anomaly may be due to loss or gain of specific genes that influence pigmentation located on the long arm of chromosome 14 in this patient.

Incontinentia pigmenti: seven cases with dental manifestations

Incontinentia Pigmenti (Bloch-Sulzberger syndrome) is an uncommon genodermatosis that usually affects female infants. The condition is characterized by four cutaneous stages and is frequently associated with dental, ocular, central nervous system and structural anomalies. A large case series of seven patients, all female, who presented to the Department of Paediatric Dentistry at the Eastman Dental Hospital over the last 16 years is reported. The dental features of these cases were typical and included missing teeth, microdontia and delayed eruption. In two of the seven cases, both maxillary canines were palatally impacted.

Functional X-chromosomal mosaicism of the skin: Rudolf Happle and the lines of Alfred Blaschko

In this article, the contribution of Rudolf Happle to the understanding of X-linked skin diseases is reviewed. In 1977 he proposed functional X-chromosomal mosaicism as the genetic mechanism underlying cutaneous anomalies that were seen in a number of X-linked skin diseases such as incontinentia pigmenti or focal dermal hypoplasia. Moreover, he recognized that these cutaneous anomalies followed the lines of Blaschko and thus he could tie in the development of the lines of Blaschko with a datable embryonic event. Convincing proof for the concept of functional X-chromosomal mosaicism was later provided by his group from functional sweat studies in female carriers of the X-linked gene defect hypohidrotic ectodermal dysplasia showing again on the back of the patient a gross, fountain-like mosaic typical of the lines of Blaschko. Moreover, in the years 1977 to 1981 he recognized the mosaic pattern in a syndrome of chondrodysplasia punctata, linear ichthyosis, patchy cicatricial alopecia, unilateral cataracts, and short stature again as a functional X-chromosomal mosaic becoming manifest exclusively in women and proposed that this syndrome, which is today named after him, is because of an X-linked dominant gene defect. Finally, the puzzling molecular genetics of the Happle syndrome are reviewed. Most likely, the Happle syndrome gene is not lethal for hemizygously affected males but rather similar to the example of epilepsy with mental retardation limited to females, the gene actually spares male gene carriers.

X-linked mental retardation syndrome with short stature, small hands and feet, seizures, cleft palate, and glaucoma is linked to Xq28

Of the gene-rich regions of the human genome, Xq28 is the most densely mapped. Mutations of genes in this band are responsible for 10 syndromal forms of mental retardation and 5 nonsyndromal forms. Clinical and molecular studies reported here add an additional syndromic form of X-linked mental retardation (XLMR) to this region. The condition comprises short stature, small hands and feet, seizures, cleft palate, and glaucoma. One affected male died at age 19 years in status epilepticus, but others have survived to old age. Carrier females do not have somatic anomalies or mental impairment. The gene is localized to the terminal 8 Mb of Xq28 with markers distal to DXS8011 showing linkage to the disorder with a lod score of 2.11 at zero recombination.

X-inactivation and marker studies in three families with incontinentia pigmenti: implications for counselling and gene localisation

Familial incontinentia pigmenti (IP) is an X-linked dominant disorder with an extremely variable clinical presentation. Ambiguous diagnosis can complicate genetic counselling and attempts to refine the gene location in Xq28. Marked skewing of X-inactivation patterns is a hallmark of IP and provides a means for investigating uncertain cases. We have conducted X-inactivation studies in three families where Xq28 marker studies were at odds with the original clinical assessment. The results indicate that no recombination between the disease locus and Xq28 loci has occurred and suggest that mosaicism is responsible for the discrepancy in one family.

Incontinentia pigmenti

This article reviews the clinical features, histopathology, genetics, and differential diagnosis of incontinentia pigmenti. Emphasis is placed on appropriate management strategies for patients with incontinentia pigmenti.

A comparative transcription map of the murine bare patches (Bpa) and striated (Str) critical regions and human Xq28

The X-linked developmental mouse mutations bare patches (Bpa) and striated (Str) may be homologous to human X-linked dominant chondrodysplasia punctata (CDPX2) and incontinentia pigmenti (IP2), respectively, based on their genetic mapping and clinical phenotypes. Bpa and Str have been localized to an overlapping critical region of 600 kb that demonstrates conserved gene order with loci in human Xq28 between DXS1104 and DXS52. As part of efforts to isolate the genes involved in these disorders, we have begun to develop a comparative transcription map spanning this region in both species. Using techniques of cross-species conservation and hybridization, exon trapping, and cDNA selection we have identified four known genes or members of gene families--caltractin, a member of the gamma-aminobutyric acid (GABAA) receptor gene family, a member of the melanoma antigen gene (MAGE) family, and several members of the murine-specific, X-linked lymphocyte regulated gene (Xlr3) family. Trapped exons and, in some cases, longer cDNAs have been isolated for potentially 7-9 additional genes. One cDNA demonstrates highly significant homology with members of the Krüppel family of zinc finger transcription factors. A second novel cDNA demonstrates homology at the 3' end of the predicted amino acid sequence to a LIM domain consensus. Gene order appears conserved among those cDNAs determined to be present in both human and mouse. Three of the murine transcripts appear to be present in multiple copies within the Bpa/Str critical region and could be associated with a predisposition to genomic rearrangements. Reverse transcriptase PCR (RT-PCR) and Northern analysis demonstrate that several of the transcripts are expressed in mid-gestation murine embryos and neonatal skin, making them candidates for the Bpa and Str mutations and their respective homologous human disorders.

X inactivation analysis in a female with hypomelanosis of Ito associated with a balanced X;17 translocation: evidence for functional disomy of Xp

X inactivation analysis was performed on normal and hypopigmented skin samples obtained from a female with hypomelanosis of Ito associated with a balanced whole arm X;17 translocation. Severe skewing of X inactivation resulting in inactivity of the intact X was found in blood and cultures of both types of skin, but analysis of DNA prepared directly from hypopigmented skin showed significant inactivation of the translocated X, inconsistent with the usual mechanism of phenotypic expression in X;autosome translocations. In addition, dual colour FISH analysis using centromere specific probes for chromosomes X and 17 showed that the breakpoints on both chromosomes lie within the alphoid arrays, making interruption of a locus on either chromosome unlikely. While partial variable monosomy of loci on chromosome 17p cannot be excluded as contributing to the phenotype in this patient, it is argued that the major likely factor is partial functional disomy of sequences on Xp in cell lineages that have failed to inactivate the intact X chromosome.

Hypomelanosis of Ito and X;autosome translocations: a unifying hypothesis

Hypomelanosis of Ito is a sporadic multisystem disorder known to be associated in many cases with chromosomal mosaicism. While no particular pattern is generally evident for the specific chromosomes involved in such patients, a subgroup of female patients exists in whom the common factor is the presence of a balanced, constitutional X;autosome translocation, with a cytogenetic breakpoint in the pericentromeric region of the X. It is argued here that the phenotype in these cases results not from the interruption of X linked genes but from the presence of mosaic functional disomy of X sequences above the breakpoint.

[Incontinentia pigmenti]

Incontinentia pigmenti (IP) is a hereditary syndrome characterized by specific skin lesions occurring mostly during the neonatal period (96% of the cases before 6 weeks of age). These skin lesions have four steps of evolution: inflammatory or erythemato-bullous stage (very often associated with peripheral blood hyper-eosinophilia), proliferative or verruco-lichenoid stage, pigmentary or terminal stage characterized by "fountain" or "firework" features (with a picture of pigmentary incontinence at histological examination), sometimes there is a fourth stage referred to as "involutive". Ocular and neurological involvement is the main determinant in the prognosis. Eye lesions include corneal flecks, cataracts, uveitis or optical atrophy with retrolental fribroplasia. The neurological involvement includes pyramidal syndrome, cerebral ataxia, microcephalia, and mental retardation. The disease has mainly an X-linked dominant transmission and is usually lethal for males. Rare cases are observed in boys, some being associated with Klinefelter syndrome. Research is ongoing to identify the IP gene on the X chromosome. In the family form of IP, the gene has been located on chromosome Xq28, which allows prenatal diagnosis using trophoblast biopsy.

Gonadal mosaicism for incontinentia pigmenti in a healthy male

Incontinentia pigmenti (IP) is a genodermatosis that segregates as an X linked dominant trait with male lethality. The disease has been linked to Xq28 in a number of studies. A few affected males have been documented, most of whom have a 47,XXY karyotype. We report a family with two paternally related half sisters, each affected with IP. The father is healthy, clinically normal, and has a 46,XY normal male karyotype. Linkage analysis of 12 polymorphic markers (two X linked and 10 autosomal) confirms paternity. X inactivation studies with the human androgen receptor (HUMARA) indicate that the paternal X chromosome is inactivated preferentially in each girl, implying that this chromosome carries the IP mutation, and that the father is a gonadal mosaic for the IP mutation.

Incontinentia pigmenti: late sequelae and genotypic diagnosis: a three-generation study of four patients

Late cutaneous signs of incontinentia pigmenti (IP) are often subtle and misdiagnosed. We focus on these somewhat confusing clinical markers in a family, and on the genotypic diagnosis based on DNA analysis. An infant was born with a typical IP rash. Dermatologic examination of the women in her family revealed that her mother, her maternal aunt, and her grandmother had subtle skin signs reminiscent of IP. The four family members proved to be informative for DNA markers in the Xq28 region. Familial cases of IP are sometimes missed due to the lack of recognition of some late skin signs that are not always hyperpigmented streaks. Subtle, faint, hypochromic or atrophic lesions in a linear pattern may occur. Thus an accurate diagnosis of the women in a particular family also requires anamnestic data and recognition of extracutaneous anomalies. When a clinical diagnosis has been made, DNA marker analysis allows us to offer a prenatal diagnosis with minimal risk of error in case of further pregnancy. However, early testing of chorionic villus samples does not allow one to predict the severity of the disease in an affected fetus.

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.

Familial linear and whorled nevoid hypermelanosis

Two patients with familial linear and whorled nevoid hypermelanosis, a 33-year-old woman and her 3-month-old daughter, are described. These are the first cases of linear and whorled nevoid hypermelanosis of familial occurrence reported in the literature. Asymptomatic hyperpigmented macules in streaky configurations had appeared on the trunk and extremities of both patients several weeks after birth and then gradually spread. No previous inflammation or eruption was observed. Histologic examination revealed a slight increase in the number of melanocytes in the epidermis and an irregular basal melanosis. No pigmentary incontinence or melanophages were observed in the dermis. Ultrastructurally the only finding was an increase in the number of normal-appearing mature melanosomes in keratinocytes in the lesion. Chromosomal analysis of cultured peripheral blood lymphocytes and dermal fibroblasts from normal and pigmented skin revealed no evidence of mixoploidy or chimerism. An undescribed genetic abnormality is suggested as the cause.

X-linked mental retardation exhibiting linkage to DXS255 and PGKP1: a new MRX family (MRX14) with localization in the pericentromeric region

Gene localization was determined by linkage analysis in a large French family with X-linked mental retardation (MRX). Seven living affected males were clinically studied and the clinical picture was characterized by moderate to severe mental handicap with poor secondary speech acquisition. Seizures, slight microcephaly, simian crease, anteverted pinnae, and macroorchidism were observed in some patients only. Linkage analysis revealed no recombination between the MRX gene and two loci: DXS255 at Xp11.22 (Zmax = 3.31 at theta = 0.00) and PGKP1 at Xq11.2-q12 (Zmax = 3.08 at theta = 0.00). One recombination was observed between the gene and the two loci DXS164 at Xp21.2 and DXS441 at Xq13.3, respectively. These results suggested gene localization in the pericentromeric region of the X chromosome, and the LOD scores justified assignment of the symbol MRX14 to this family.

Unstable pre-mutation may explain mosaic disease expression of incontinentia pigmenti in males

Mosaic skin lesions following the lines of Blaschko are found in boys affected by incontinentia pigmenti (IP). For an X-linked gene defect, this is rather surprising. To explain the mosaic disease expression of IP in males, we propose that the disease is caused by an unstable pre-mutation, which normally remains silent in males during early embryogenesis. Occasionally "silencing" is incomplete and gives rise to clinical manifest IP reflecting a mosaic state of alleles with the full and the pre-mutation in the same patient. This model can account for mother-to-son transmission of IP and for disparate phenotypes in monozygotic female twins.

Retinal and other manifestations of incontinentia pigmenti (Bloch-Sulzberger syndrome)

BACKGROUND

One of the largest series of patients with incontinentia pigmenti who have undergone detailed ophthalmologic examination is reported here, including previously unrecognized findings with visually disabling consequences.

METHODS

Thirteen females with incontinentia pigmenti from eight unrelated families were evaluated. The diagnosis of incontinentia pigmenti had been established previously by a referring pediatrician or dermatologist in 12 patients and by the authors in one other patient on the basis of retinal findings and history of characteristic skin manifestations.

RESULTS

Abnormalities of the eye, central nervous system, skeleton, teeth, and hair develop in a majority of patients. The authors describe the evolution of retinal vascular abnormalities, and, for the first time, document foveal hypoplasia (in 4 of their 13 patients). The authors also provide the first report of a child with a normal brain shown on computed tomographic scan at 3 days old, which evolved to devastating cerebral ischemia, edema, and cortical blindness beginning at 6 days old.

CONCLUSIONS

Incontinentia pigmenti should be included in the differential diagnosis of patients with peripheral retinal vascular nonperfusion, preretinal neovascularization, infantile retinal detachment, or foveal hypoplasia, particularly if there is evidence of characteristic dermatologic or other systemic manifestations. In infants with incontinentia pigmenti, retinal vascular anomalies are best detected by examination under anesthesia using fluorescein angiography.

Recent developments in certain X-linked genetic eye disorders

Over the past few years, genetic diseases of the ocular system have become very active and fast-growing research areas in the vision field. The rapid development of the recombinant DNA techniques together with somatic cell genetics, during the last two decades has fueled this progress. As a result, many genetic disease genes have been localized in the human chromosome and several of them have been isolated and characterized. These and other studies have profoundly enriched our basic understanding of genetic eye disorders. Although gene replacement therapy, prenatal diagnosis and carrier detection have not been extensively tried for genetic eye diseases, such attempts will now be feasible. Molecular analyses made it clear that there are many challenging problems that need attention. This report highlights some of these initial developments, particularly on the X-linked major genetic eye diseases. In order to help the beginners and general audience, a brief description of the clinical pathology and the molecular probes used to locate the genetic defects of certain disorders are presented. Disorders are arranged according to their linkage from telomere to telomere on the chromosome to give a coherent structure. It is hoped that this information is useful and of general interest for the beginners, established investigators and ophthalmologists.

Incontinentia pigmenti: transmission from father to daughter

Incontinentia pigmenti (IP) is a well-described genodermatosis that occurs almost exclusively in females. IP is characterized by a distinctive skin eruption and a variable presence of multisystem abnormalities. Pedigree analysis is most consistent with an X-linked dominant trait that is lethal in males. However, 27 reports of IP in males have been published, excluding four patients who had Klinefelter's syndrome. It has usually been assumed that these rare affected males survive because of genetic mosaicism. Mosaic inheritance of IP is also strongly supported by the characteristic distribution of skin findings along Blaschko's lines. Only one case of father-to-daughter transmission has been previously reported. We report a second case of father-to-daughter transmission of IP. Chromosomal analysis of blood and fibroblasts from the father failed to provide evidence of genetic mosaicism.

Incontinentia pigmenti achromians (hypomelanosis of ITO, MIM 146150): further evidence of localization at Xp11

We report on a girl with apparent hypomelanosis of Ito (ITO); cytogenetic studies disclosed the karyotype 46,X,t(X;10)(p11;q11)mat. We present further evidence that at least one of the genetic forms of ITO is located at Xp11; reviewing the clinical characteristics of patients with incontinentia pigmenti type 1 (IP1) and ITO with X-autosome translocations, we suggest that IP1 and ITO represent allelic forms or a contiguous gene syndrome. Thus, different genetic alterations in this region (Xp11) give rise to ITO or IP1 or borderline phenotypes. We also suggest that all patients with ITO, due to Xp11 mutation, have functional or genetic mosaicisms.

Genetic mapping of the X-linked dominant mutations striated (Str) and bare patches (Bpa) to a 600-kb region of the mouse X chromosome: implications for mapping human disorders in Xq28

Striated (Str) and bare patches (Bpa) are X-irradiation-induced, X-linked dominant mouse mutations that are lethal prenatally in hemizygous males. To map the Str mutation, we generated a backcross involving Mus castaneus. Pedigree analysis of 193 affected female and normal male progeny from the cross places Str extremely close to DXMIT1 and favors a gene order of (Cf-9)-Ids-Gabra3-DXS1104h-(Str, DXMIT1)-F8a-DXPas8-DXBay6-DXMIT6 for the loci studied. This region of the mouse X Chromosome (Chr) is syntenic with proximal human Xq28. Based on the mode of inheritance and clinical phenotype, Str may be a homolog of human familial incontinentia pigmenti (IP2). Further refinement of our genetic mapping of bare patches positions that locus between DXS1104h and DXPas8 in the same region as Str, raising the possibility that Bpa and Str may be allelic or are due to mutations in overlapping contiguous genes.

Incontinentia pigmenti (Bloch-Sulzberger syndrome)

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