Father-to-daughter transmission of focal dermal hypoplasia associated with nonrandom X-inactivation: support for X-linked inheritance and paternal X chromosome mosaicism

[Focal dermal hypoplasia associated with pathogenic PORCN gene variant in postzygotic, unilateral mosaic form]

We report a case of a 29-year-old woman with subtle partial erythematous, partial hyperpigmented streaks along the Blaschko's lines on the right side of the body since early childhood. Primary DNA results of the skin and blood assay diagnosed focal dermal hypoplasia in mosaic form. The postzygotic mutation in the PORCN gene was only detectable in the affected skin and not in the blood assay. This article illustrates that clinically very discrete hypopigmentation and poikiloderma along Blaschko lines should raise awareness for robust diagnostic analysis in order to recognize this variable multisystem disease and to ensure an appropriate search for extracutaneous abnormalities and human genetic counseling, ideally before pregnancy. Careful correlation of clinical, histological, and genetic features along with close multidisciplinary cooperation of specialists from the fields of human genetics, dermatology, pediatrics, orthopedics and ophthalmology is crucial for final diagnosis, assessment of the prognosis and targeted genetic counseling of affected individuals.

Mosaicism due to postzygotic mutations in women with focal dermal hypoplasia

Focal dermal hypoplasia (FDH, Goltz syndrome, MIM #305600) constitutes a rare multisystem genetic disorder of the skin, skeleton, teeth and eyes with considerable variation in the clinical features. FDH is transmitted as an X-linked dominant trait and is caused by mutations in PORCN. In male children, hemizygous PORCN mutations are lethal in utero. Around 300 cases have been reported in the literature to date. About 10% of them are male patients presenting with either Klinefelter syndrome (karyotype 47, XXY) or mosaicism of a postzygotic mutation. Here we describe four cases of women with typical features of FDH, in whom a PORCN mutation was found in DNA from affected cutaneous tissue but not in DNA from peripheral blood. This study suggests that mosaicism caused by a postzygotic mutation occurs more often than assumed to date in female patients with FDH. A negative analysis performed on peripheral blood DNA does not exclude the diagnosis of FDH and it is therefore of practical importance to analyse DNA from the affected skin in order to identify low-level mosaicism and thus to improve diagnostic precision. In total, we found two missense variants, one novel indel and one novel splice-site variant. Individuals harbouring postzygotic mosaicism run a risk of transmitting the disorder to their daughters, because the maternal mosaic could also affect the gonads.

Unilateral Focal Dermal Hypoplasia (Goltz Syndrome): Case Report and Literature Review

Focal dermal hypoplasia (FDH) or Goltz syndrome is a rare X-linked dominant multisystemic disease involving the ectoderm, mesoderm, and endoderm. About 95% of the cases appear de novo, and 90% of them are females. Recently, the studies revealed that FDH is caused by a mutation in the PORCN gene. We report a case of unilateral FDH or Goltz syndrome in a 16-year-old girl presenting with hypopigmented-reticulated atrophic macules and patches in a linear pattern distributed along the lines of Blaschko over the right side of the face and the right arm. Also she is having hypoplasia of the right breast with dental enamel abnormality and partial anodontia in the lower jaw. Sparse hair and partial alopecia on the right side (scalp, eyebrows, and eyelashes) were also observed.

A non-mosaic PORCN mutation in a male with severe congenital anomalies overlapping focal dermal hypoplasia

Mutations in the PORCN gene cause the X-linked dominant condition focal dermal hypoplasia (FDH). Features of FDH include striated pigmentation of the skin, ocular and skeletal malformations. FDH is generally associated with in utero lethality in non-mosaic males and most of the currently reported male patients show mosaicism due to de novo post-zygotic mutations in the PORCN gene. There is only one previous report of a surviving male with an inherited mutation in the PORCN gene. Here, we report two male siblings with multiple malformations including skeletal, ocular and renal defects overlapping with FDH. A novel PORCN mutation (p.Ser250Phe) was identified in a non-mosaic, hemizygous state in one of the siblings who survived to 8 years of age. The mother is a heterozygous carrier, has a random X-inactivation pattern and is asymptomatic. Findings unusual for FDH include dysplastic clavicles and bilateral Tessier IV facial clefts. This is the second case report of a non-mosaic PORCN mutation in a male individual with multiple congenital anomalies. While the pathogenicity of this mutation remains to be further investigated, the survival of a male with a non-mosaic mutation in PORCN is suggestive of a functionally mild mutation leading to an X-linked recessive mode of inheritance.

Goltz syndrome: a rare case of father-to-daughter transmission

An 8-year-old girl presented to us with skin-coloured to yellowish soft compressible papules, intermixed with hypopigmented and hyperpigmented macules in a Blaschkoid pattern, and 'lobster-claw deformity' affecting her bilateral feet. Additional examination findings included short stature, facial asymmetry, low-set ears, hypodontia, enamel hypoplasia, tonsillar enlargement and spina-bifida occulta at S1-3 vertebral level. A diagnosis of Goltz syndrome was suspected clinically, which was confirmed on skin biopsy. Her father also had hypopigmented and hyperpigmented macules in a Blaschkoid distribution, 'lobster-claw' deformity and kyphoscoliosis. None of the other family members were affected.

Determining the role of skewed X-chromosome inactivation in developing muscle symptoms in carriers of Duchenne muscular dystrophy

Duchenne and Becker dystrophinopathies (DMD and BMD) are X-linked recessive disorders caused by mutations in the dystrophin gene that lead to absent or reduced expression of dystrophin in both skeletal and heart muscles. DMD/BMD female carriers are usually asymptomatic, although about 8 % may exhibit muscle or cardiac symptoms. Several mechanisms leading to a reduced dystrophin have been hypothesized to explain the clinical manifestations and, in particular, the role of the skewed XCI is questioned. In this review, the mechanism of XCI and its involvement in the phenotype of BMD/DMD carriers with both a normal karyotype or with X;autosome translocations with breakpoints at Xp21 (locus of the DMD gene) will be analyzed. We have previously observed that DMD carriers with moderate/severe muscle involvement, exhibit a moderate or extremely skewed XCI, in particular if presenting with an early onset of symptoms, while DMD carriers with mild muscle involvement present a random XCI. Moreover, we found that among 87.1 % of the carriers with X;autosome translocations involving the locus Xp21 who developed signs and symptoms of dystrophinopathy such as proximal muscle weakness, difficulty to run, jump and climb stairs, 95.2 % had a skewed XCI pattern in lymphocytes. These data support the hypothesis that skewed XCI is involved in the onset of phenotype in DMD carriers, the X chromosome carrying the normal DMD gene being preferentially inactivated and leading to a moderate-severe muscle involvement.

Goltz syndrome and PORCN mosaicism

Goltz syndrome, also known as focal dermal hypoplasia, is characterized primarily by ectodermal and mesodermal defects. Manifestations include cutis aplasia, dermal hypoplasia, papillomas, chorioretinal colobomas, absent/dysplastic teeth, and skeletal anomalies. Goltz syndrome is an X-linked disorder due to mutations in PORCN, with a predominance of females affected. Germline mutations in PORCN are thought to result in embryonically lethality in males. We present a boy with a phenotype consistent with Goltz syndrome with low-level mosaicism for a novel mutation in PORCN from peripheral blood (c.956dupA; p.Asn320GlufsX99).

Focal dermal hypoplasia due to a novel mutation in a boy with Klinefelter syndrome

A boy was born with multiple anomalies, including right hemifacial microsomia, eye abnormalities, syndactyly, right hand ectrodactyly, hypoplastic nails, omphalocele, bladder exstrophy, renal dilatation, and splayed symphysis pubis. The skin was also abnormal, with atrophic skin plaques and areas of telangiectasia along the lines of Blaschko. The karyotype was 47,XXY (Klinefelter syndrome). He was found to have a heterozygous mutation in the PORCN gene. He exhibited the classical features of focal dermal hypoplasia. Fewer than 15% of reported cases are male when it is thought to be due to postzygotic mutation and thus mosaic. This is the first reported boy to have heterozygous mutation for Goltz syndrome who survived due to the extra X chromosome.

Deletion of Porcn in mice leads to multiple developmental defects and models human focal dermal hypoplasia (Goltz syndrome)

BACKGROUND

Focal Dermal Hypoplasia (FDH) is a genetic disorder characterized by developmental defects in skin, skeleton and ectodermal appendages. FDH is caused by dominant loss-of-function mutations in X-linked PORCN. PORCN orthologues in Drosophila and mice encode endoplasmic reticulum proteins required for secretion and function of Wnt proteins. Wnt proteins play important roles in embryo development, tissue homeostasis and stem cell maintenance. Since features of FDH overlap with those seen in mouse Wnt pathway mutants, FDH likely results from defective Wnt signaling but molecular mechanisms by which inactivation of PORCN affects Wnt signaling and manifestations of FDH remain to be elucidated.

RESULTS

We introduced intronic loxP sites and a neomycin gene in the mouse Porcn locus for conditional inactivation. Porcn-ex3-7flox mice have no apparent developmental defects, but chimeric mice retaining the neomycin gene (Porcn-ex3-7Neo-flox) have limb, skin, and urogenital abnormalities. Conditional Porcn inactivation by EIIa-driven or Hprt-driven Cre recombinase results in increased early embryonic lethality. Mesenchyme-specific Prx-Cre-driven inactivation of Porcn produces FDH-like limb defects, while ectodermal Krt14-Cre-driven inactivation produces thin skin, alopecia, and abnormal dentition. Furthermore, cell-based assays confirm that human PORCN mutations reduce WNT3A secretion.

CONCLUSIONS

These data indicate that Porcn inactivation in the mouse produces a model for human FDH and that phenotypic features result from defective WNT signaling in ectodermal- and mesenchymal-derived structures.

Focal dermal hypoplasia in a male patient due to mosaicism for a novel PORCN single nucleotide deletion

BACKGROUND

Focal dermal hypoplasia (FDH) is an X-linked dominant disorder caused by nonsense mutations and deletions in the PORCN gene coding for a transmembrane endoplasmic reticulum protein required for Wingless signalling. Symptoms consist mainly of linear atrophic skin defects, skeletal deformities and, in many cases, mental retardation. Osteopathia striata is a nearly constant feature. Approximately 90% of patients are women. A few instances of father-to-daughter transmission and a number of sporadic male cases presumably as a result of somatic mosaicism have been recorded.

OBJECTIVES

The aim of this study was to demonstrate the presence of somatic mosaicism for PORCN mutations in a male patient.

METHODS

We sequenced the PORCN gene in different tissues from a boy with symptoms of FDH.

RESULTS

We demonstrate post-zygotic mosaicism for a novel deletion in the PORCN gene.

CONCLUSIONS

A novel PORCN deletion, present in a post-zygotic mosaic, causes focal dermal hyplasia in a male patient.

Mutations in X-linked PORCN, a putative regulator of Wnt signaling, cause focal dermal hypoplasia

Focal dermal hypoplasia is an X-linked dominant disorder characterized by patchy hypoplastic skin and digital, ocular and dental malformations. We used array comparative genomic hybridization to identify a 219-kb deletion in Xp11.23 in two affected females. We sequenced genes in this region and found heterozygous and mosaic mutations in PORCN in other affected females and males, respectively. PORCN encodes the human homolog of Drosophila melanogaster porcupine, an endoplasmic reticulum protein involved in secretion of Wnt proteins.

Focal dermal hypoplasia: ultrastructural abnormalities of the connective tissue

We followed over 10 years three girls with focal dermal hypoplasia syndrome. The histopathological changes demonstrated at the optical level an hypoplastic dermis with thin and scarce collagen bundles and a marked diminution of elastic fibers. Mature adipose tissue was found scattered within the papillary and reticular dermis. No alterations in the basal membrane were observed by immunocytochemical or ultrastructural techniques. Ultrastructurally, in the skin-affected areas, loosely arranged collagen bundles composed of few fibrils were seen scattered in the extracellular matrix. Scarce elastic fibers of normal morphology were also observed. Fibroblasts were smaller, oval-shaped, and diminished in number with a poorly developed cytoplasm. In these fibroblasts, the most conspicuous feature was a remarkable and irregular thickening of the nuclear fibrous lamina. Taking into account that a common link between all laminopaties may be a failure of stem cells to regenerate mesenchymal tissue, this failure would induce the dermal hypoplasia observed in our patients presenting Goltz syndrome.

Ocular coloboma: a reassessment in the age of molecular neuroscience

Congenital colobomata of the eye are important causes of childhood visual impairment and blindness. Ocular coloboma can be seen in isolation and in an impressive number of multisystem syndromes, where the eye phenotype is often seen in association with severe neurological or craniofacial anomalies or other systemic developmental defects. Several studies have shown that, in addition to inheritance, environmental influences may be causative factors. Through work to identify genes underlying inherited coloboma, significant inroads are being made into understanding the molecular events controlling closure of the optic fissure. In general, severity of disease can be linked to the temporal expression of the gene, but this is modified by factors such as tissue specificity of gene expression and genetic redundancy.

Focal dermal hypoplasia with exuberant fat herniations and skeletal deformities

Focal dermal hypoplasia or Goltz syndrome is a rare congenital and mesoectodermal dysplasia with multisystemic involvement. Although the genetic alterations responsible for focal dermal hypoplasia are not fully known, there is predominance in affected females, suggesting dominant X-linked inheritance. Besides the skin, other structures frequently involved are the skeletal system, eyes, teeth, hair, and nails. Skeletal abnormalities are predominantly observed in the hands and feet. We report a 9-year-old girl who had typical linear skin atrophy on the trunk, exuberant "fat herniations," several skeletal abnormalities, and exuberant "lobster claw" deformity. In addition, she had the typical longitudinal striations in femur metaphyses. With regard to family history, her mother had one male stillbirth with several deformities. This typical focal dermal hypoplasia patient is considered valuable in light of the affected male stillbirth and parents with nonaffected phenotypes that together provides evidence for mother-to-daughter spontaneous transmission.

Enamel defects and Lyonization in focal dermal hypoplasia

We report a pattern of enamel hypoplasia in focal dermal hypoplasia similar to that found in females with X-linked amelogenesis imperfecta. Three cases of focal dermal hypoplasia are described, with specific focus on the oral and dental features. In these cases the teeth all had vertical grooving with notching of the incisal or cuspal tips. Also recorded were blunt roots of taurodont form with open apices and missing teeth in 1 case. Oral papillomas were present in 2 cases. The pattern of enamel defects is attributed to Lyonization, which is consistent with the pattern of skin and bone lesions typically seen in focal dermal hypoplasia. This supports the proposal that focal dermal hypoplasia is X-linked. The authors conclude that the pattern of dental defects in focal dermal hypoplasia is consistent with Lyonization.

Three cases of focal dermal hypoplasia (Goltz syndrome)

Focal dermal hypoplasia or Goltz syndrome is a rare genodermatosis, characterized by multiple abnormalities of ectodermal and mesodermal origin. It is found predominantly in females and is characterized by hypoplasia of skin and papillomas. Three cases of focal dermal hypoplasia in infancy with unusual inheritance patterns are reported. Cutaneous features were atrophic reticulated scars involving the trunk and extremities following the lines of Blaschko. Papillomas were present on the genitalia and in a periorificial distribution. Skeletal abnormalities included syndactyly, polydactyly and lobster claw deformities. Ophthalmological examination revealed strabismus and retinal colobomas.

Oculo-facio-cardio-dental syndrome: skewed X chromosome inactivation in mother and daughter suggest X-linked dominant Inheritance

Oculo-facio-cardio-dental syndrome (OFCD) is an uncommon multiple congenital anomaly syndrome that is characterized by congenital cataracts, multiple minor facial dysmorphic features, congenital heart defects, and dental anomalies including canine radiculomegaly and oligodontia. Although most cases of OFCD are sporadic, since all reported OFCD individuals have been female, it has been suggested that OFCD is an X-linked dominant trait. Here we report two affected female patients with OFCD, a mother and daughter, who both had congenital cataracts, microphthalmia, characteristic dental anomalies, and typical facial dysmorphisms. These features were diagnostic for OFCD; thus, these cases represent the second documented instance of mother-to-daughter OFCD transmission. In addition to the clinical features typically seen in OFCD individuals, the affected daughter exhibited several additional congenital anomalies including intestinal malrotation and hypoplastic thumbs. Thus, these cases further define and expand the OFCD clinical phenotype. These two individuals also displayed a skewed pattern of X chromosome inactivation. Together, these data strongly support the hypothesis that OFCD is inherited as an X-linked dominant condition.

Melanocyte stimulation in focal dermal hypoplasia with unusual pigmented skin lesions: a histologic and immunohistochemical study

Focal dermal hypoplasia (FDH) or Goltz syndrome is a rare genodermatosis transmitted in a dominant, X-linked mode. It is characterized clinically by atrophic skin lesions, multiple mucocutaneous papillomas, hyperpigmented linear skin lesions, and several skeletal and visceral anomalies. We followed over several years a female patient with FDH, who had the characteristic atrophic cutaneous lesions and periorificial papillomas, who developed at the periphery of atrophic lesions peculiar lentigo-like pigmented macules. Immunohistologically, increased melanin deposits within the epidermis and the dermis were seen, produced by stimulated epidermal melanocytes expressing the HMB-45 antigen. These findings further support the contention that cutaneous lesions of FDH may be progressive, and provide a physiopathologic basis for understanding the hyperpigmented lesions of FDH.

Skewed X-chromosome inactivation is a common feature of X-linked mental retardation disorders

Some deleterious X-linked mutations may result in a growth disadvantage for those cells in which the mutation, when on the active X chromosome, affects cell proliferation or viability. To explore the relationship between skewed X-chromosome inactivation and X-linked mental retardation (XLMR) disorders, we used the androgen receptor X-inactivation assay to determine X-inactivation patterns in 155 female subjects from 24 families segregating 20 distinct XLMR disorders. Among XLMR carriers, approximately 50% demonstrate markedly skewed X inactivation (i.e., patterns > or =80:20), compared with only approximately 10% of female control subjects (P<.001). Thus, skewed X inactivation is a relatively common feature of XLMR disorders. Of the 20 distinct XLMR disorders, 4 demonstrate a strong association with skewed X inactivation, since all carriers of these mutations demonstrate X-inactivation patterns > or =80:20. The XLMR mutations are present on the preferentially inactive X chromosome in all 20 informative female subjects from these families, indicating that skewing is due to selection against those cells in which the XLMR mutation is on the active X chromosome.

[Focal dermal hypoplasia: description of three cases]

BACKGROUND

Focal dermal hypoplasia syndrome is mainly defined by the association of abnormalities of extremities, atrophy and linear hyperpigmentation of the skin, localized deposits of superficial fat, anomalies of the eyes and of the nails. Neonates are often small for their age.

CASE REPORTS

Three sporadic cases are reported. Mental delay and omphalocele were observed in the first case. The neurological development was subnormal in the second and an unusual monodactyly was seen in the third.

CONCLUSION

Most cases are sporadic, but in family cases, an X-linked dominant factor is likely. When a first affected offspring is observed, skin examination and X-ray should be carried out in parents to evaluate the risk of recurrence in their children. As the gene site has not yet been determined, antenatal diagnosis should be suspected on echography when fetal growth delay is associated to distal limb and/or ocular anomalies.

Cloning and characterization of a novel rho-type GTPase-activating protein gene (ARHGAP6) from the critical region for microphthalmia with linear skin defects

Microphthalmia with linear skin defects syndrome (MLS) is an X-linked dominant, male-lethal disorder associated with chromosomal rearrangements that result in deletions of the distal short arm of the X chromosome. In an effort to isolate expressed sequences from the 500-kb MLS critical region in Xp22.3, exons were trapped from 14 overlapping cosmids. Using exon connection followed by cDNA library screening, we identified a 2.4-kb contig of cDNA library screening 170 kb of genomic sequence in the MLS deletion region. Northern analysis of this cDNA detected a prominent approximately 4.2-kb transcript and a less abundant approximately 6-kb transcript in all tissues examined, with additional transcripts in skeletal muscle. Sequence analysis revealed a coding region of 601 amino acids contained in 12 exons, with a splice variant isoform of 495 amino acids. The predicted protein sequence of the gene, named ARHGAP6, contains homology to the GTPase-activating (GAP) domain of the rhoGAP family of proteins, which has been implicated in the regulation of actin polymerization at the plasma membrane in several cellular processes. The possible role of the ARHGAP6 protein in the pathogenesis of MLS is discussed.

Focal dermal hypoplasia: four cases with widely varying presentations

We describe four patients with focal dermal hypoplasia (FDH): a girl with classic FDH, a boy with cutaneous findings, an infant with severe multisystem disease, and the infant's mother, who had previously undiagnosed FDH. These patients illustrate the classic cutaneous manifestations of FDH and the variations that can exist within a family.