Is erythrokeratoderma one disorder? A clinical and ultrastructural study of two siblings

Erythrokeratodermia variabilis et progressiva due to a novel mutation in GJB4

Erythrokeratodermia variabilis et progressiva (EKVP) is a rare genodermatosis of clinical and genetic heterogeneity, characterized by the manifestations of localized or disseminated persistent hyperkeratotic plagues and stationary to migratory transient erythematous patches. The majority of EKVP cases display an autosomal dominant mode of inheritance with incomplete penetrance, although recessive transmission has also been described. Mutations associated with EKVP have been primarily detected in connexin (Cx) genes. We herein reported a Chinese sporadic case of late-onset EKVP with a novel heterozygous missense mutation c.109G>A (p.V37M) in GJB4 (Cx30.3) gene, which resulted in a significant reduction of GJB4 expression in the epidermis of the patient. In accordance, while wild-type GJB4 localized at the cell membrane of HeLa cells forming intercellular junctions and intracellular puncta, V37M mutant variant was diffusely expressed within HeLa cells at a considerably lower level. Our findings reveal an essential role of GJB4 in the pathogenesis of EKVP and provides insights into the therapeutic potential of the disease.

Connexin channels in congenital skin disorders

Gap junctions and hemichannels comprised of connexins influence epidermal proliferation and differentiation. Significant advances in our understanding of the functional role of connexins in the skin have been made by studying the diseases caused by connexin mutations. Eleven clinically defined cutaneous disorders with an overlapping spectrum of phenotypes are caused by mutations in five different connexin genes, highlighting that disease presentation must be deciphered with an understanding of how connexin functions are affected. Increasing evidence suggests that the skin diseases produced by connexin mutations result from dominant gains of function. In palmoplantar keratoderma with deafness, the connexin 26 mutations transdominantly alter the function of wild-type connexin 43 and create leaky heteromeric hemichannels. In keratitis-ichthyosis-deafness syndrome, different connexin 26 mutations can either form dominant hemichannels with altered calcium regulation or increased calcium permeability, leading to clinical subtypes of this syndrome. It is only with detailed understanding of these subtle functional differences that we can hope to create successful pathophysiology driven therapies for the connexin skin disorders.

Erythrokeratodermia variabilis et progressiva allelic to oculo-dento-digital dysplasia

Erythrokeratodermia variabilis et progressiva (EKVP) is a genodermatosis with clinical and genetic heterogeneity, most often transmitted in an autosomal dominant manner, caused by mutations in GJB3 and GJB4 genes encoding connexins (Cx)31 and 30.3, respectively. In this issue, Boyden et al. (2015) report for the first time de novo dominant mutations in GJA1 encoding the ubiquitous Cx43 in patients with EKVP. These results expand the genetic heterogeneity of EKVP and the human disease phenotypes associated with GJA1 mutations. They disclose that EKVP is allelic to oculo-dento-digital dysplasia, a rare syndrome previously known to be caused by dominant GJA1 mutations.

No exonic mutations at GJB2, GJB3, GJB4, GJB6, ARS (Component B), and LOR genes responsible for a Chinese patient affected by progressive symmetric erythrokeratodermia with pseudoainhum

OBJECTIVE

Progressive symmetric erythrokeratodermia (PSEK) is characterized by symmetric and growing erythematous hyperkeratotic patches over the body shortly after birth, particularly trunk and limbs, the buttocks, and the face, sometimes together with palmoplantar keratoderma (PPK). The GJB2, GJB3, GJB4, GJB6, ARS (Component B), and LOR gene mutation might contribute to PSEK manifestation. This study aimed to identify sequence alteration of these genes in a Chinese PSEK patient with pseudoainhum.

METHODS

Genomic DNA was purified from the patient's peripheral blood. Mutation analysis of target genes was performed by direct sequencing using ABI 3730 sequencer

RESULTS

No exonic mutations was identified in the aforementioned genes.

CONCLUSIONS

The result underlines the genetic heterogeneity of PSEK and other related erythrokeratodermas.

Progressive symmetric erythrokeratoderma with nephrotic syndrome: Coincidence or new association?

Progressive symmetric erythrokeratoderma (PSEK) is a rare genodermatosis with variable inheritance. It is characterized by symmetrical, erythematous, and hyperkeratotic plaques on the extremities. We report a case of a 15-year-old boy with PSEK of autosomal recessive inheritance associated with nephrotic syndrome.

The missense mutation G12D in connexin30.3 can cause both erythrokeratodermia variabilis of Mendes da Costa and progressive symmetric erythrokeratodermia of Gottron

Progressive symmetric erythrokeratoderma of Gottron (PSEK) is commonly distinguished from erythrokeratodermia variabilis Mendes da Costa (EKV). However, conclusive proof that the disorders are identical is still lacking. We performed mutation analysis and microsatellite haplotyping in two independently referred patients with PSEK and three patients from a previously published family with EKV. All patients had the same mutation in the GJB4 gene causing the amino acid substitution p.Gly12Asp (G12D). Haplotype analysis showed that all five patients had the same allelic haplotype over 2 Mb covering the disease locus. Apparently, the same GJB4 mutation may cause either an EKV or a PSEK phenotype. A single ancestral founder might have introduced EKV in the Netherlands.

A case of erythrokeratoderma variabilis: Loosened gap junctions in the acanthotic epidermis

A 15-year-old Japanese female without contributory personal or family medical history had demonstrated irregular, keratotic plaques in the lower extremities since infancy that had been gradually enlarging. The keratotic plaques showed partial erythematous change, which altered shape over a relatively short period, leaving pigmentation. The biopsy specimen taken from the erythematous, keratotic plaque showed typical church-spire-like papillomatosis with acanthosis, and thickening of granular and horny layers. Gene analysis targeting connexin 30.3 and 31, based on the diagnosis of erythrokeratoderma variabilis, did not demonstrate any abnormality of these genes. However, ultrastructural observation disclosed an increased amount of gap junctions, some of which showed four layers on high-powered electron microscopy, suggesting loosened connection of the plasma membrane of the keratinocytes through the gap junctions. This loosened gap junction structure was also observed in a case of lamellar ichthyosis, examined as a reference. The disturbed cell-to-cell interaction through latent damage to the gap junctions may be related to the keratotic changes of the epidermis in these skin diseases.

Clinical and Genetic Heterogeneity of Erythrokeratoderma Variabilis

The skin disease erythrokeratoderma variabilis (EKV) has been shown to be associated with mutations in GJB3 and GJB4 encoding connexin (Cx)31 and Cx30.3, respectively. Gap junctions composed of Cx proteins are intracellular channels providing a mechanism of synchronized cellular response facilitating metabolic and electronic functions of the cell. In the skin, Cx31 and Cx30.3 are expressed in the stratum granulosum of the epidermis with a suggested role in late keratinocyte differentiation. Molecular investigations of GJB3 and GJB4 were performed in five pedigrees and three sporadic cases of EKV. Mutational analyzes revealed disease-associated Cx31 or Cx30.3 mutations in only three probands of which two were novel mutations and one was a recurrent mutation. These genetic studies further demonstrate the heterogeneous nature of the erythrokeratodermas as not all individuals that were clinically diagnosed with EKV harbor Cx31 or Cx30.3 mutations.

Erythrokeratodermas: A classification in a state of flux?

The term 'erythrokeratodermas' or 'erythrokeratodermias' has been applied to a group of inherited disorders characterized by well-demarcated erythematous lesions and hyperkeratotic plaques. Connexin mutations have been demonstrated to be responsible for most cases of erythrokeratoderma variabilis but there remain some cases without demonstrated connexin mutations, suggesting genetic heterogeneity. The position of progressive symmetric erythrokeratoderma has become rather unclear. Loricin mutations have been found in some cases that clinically resemble variant Vohwinkel syndrome and other cases have features that overlap with those of erythrokeratoderma variablis. Whether progressive symmetric erythrokeratoderma exists as a distinct entity is under question.

A new type of erythrokeratoderma

We describe a Dutch man suffering from a previously undescribed erythrokeratoderma associated with palmoplantar keratoderma and circular constrictions of the fingers. No mutations were identified in the genes encoding loricrin, connexin 26, 30, 30.3, 31 and 31.1, and ARS/complex B. There are some similarities between the disorder described here and other palmoplantar keratodermas and erythrokeratodermas, but assignment to a particular disease category is not possible. Hence we propose that we have delineated a novel type of keratoderma.

Connexin disorders of the skin

Over the past decade, the molecular basis of most disorders of cornification has been unveiled. Among these, a distinct group has emerged because of primary defects in cell-cell communication due to faulty gap junction proteins also known as connexins. This review aims to delineate the cutaneous connexin disorders and to highlight intriguing genotype-phenotype correlations and emanating clinical implications.

A case of erythrokeratoderma variabilis without mutations in connexin 31

Erythrokeratoderma (EK) variabilis is a heterogeneous group of diseases characterized by migratory erythematous patches and hyperkeratotic plaques. Mutations in connexin 31 have recently been found to underlie several cases of EK variabilis. We describe a Japanese girl with extensive lesions that appeared to be a form of EK variabilis, clinically resembling genodermatose en cocardes (Degos). Our patient had characteristic migratory rosette or target-like erythematous keratotic plaques with peripheral scaling in addition to relatively fixed keratotic plaques. Sequencing of the connexin 31 gene did not detect mutations. Skin biopsy showed parakeratotic hyperkeratosis with hypergranulosis. Immunohistochemically, suprabasal keratins, involucrin and profilaggrin were unequivocally expressed, while loricrin expression was greatly diminished and deiminated K1 was undetectable. Our results confirm aetiological heterogeneity in EK. The histological features suggest disruption of keratinocyte terminal differentiation at a very late stage.

Abnormal cornified cell envelope formation in mutilating palmoplantar keratoderma unrelated to epidermal differentiation complex

Mutilating palmoplantar keratoderma represents a heterogeneous group of disorders, unified by characteristic mutilation of the fingers or toes, associated with palmoplantar keratoderma. Although loricrin gene mutations were recently reported in Vohwinkel's syndrome and erythrokeratoderma, the genetic basis of mutilating palmoplantar keratoderma is largely unexplored. We studied a family of non-Vohwinkel's syndrome, nonerythrokeratoderma mutilating palmoplantar keratoderma. The proband and his sister were similarly affected. Recessive inheritance was expected from the consanguineous family history. The patients had hyperkeratosis restricted to the palms and the soles. No other body sites were affected. Digital constriction was seen on all the fingers and the mutilation was severe on the distal interphalangeal region of several fingers. Histopathologically, hyperkeratosis without parakeratosis was seen in the lesional skin. Ultrastructural, immunohistochemical, and immunoelectron microscopic analyses revealed malformed cornified cell envelopes, the abnormal intracytoplasmic loricrin retention, and reduced deposition of loricrin to cornified cell envelopes. Involucrin and small proline-rich proteins 1 and 2 were normally distributed. Sequencing of the entire exons and exon-intron borders of loricrin gene of the patients excluded a mutation in loricrin DNA sequence. Linkage analysis excluded the possibility of causative mutation in the epidermal differentiation complex region of 1q21, including loricrin, involucrin, small proline-rich proteins, filaggrin, and trichohyalin. These data confirm the presence of non-Vohwinkel's syndrome mutilating palmoplantar keratoderma phenotype with abnormal loricrin cross-linking at the final stage of cornified cell envelope formation, which is caused by mutations outside the epidermal differentiation complex region.

Linkage studies in erythrokeratodermias: fine mapping, genetic heterogeneity and analysis of candidate genes

Erythrokeratodermias are a clinically heterogeneous group of rare autosomal dominant disorders of cornification with overlapping features including hyperkeratosis and erythema. We ascertained five extended pedigrees with different phenotypes for a linkage study. Three families presented with localized erythrokeratodermia variabilis, and one with erythrokeratodermia and ataxia. Another family had Greither disease associated with variable hyperkeratotic plaques. Despite their phenotypic differences, both erythrokeratodermia variabilis and erythrokeratodermia with ataxia map to a common region in 1p34-p35. Multipoint linkage and haplotype analyses place erythrokeratodermia variabilis between the marker D1S496 and D1S186 with a maximum LOD score of 12.88. Our linkage results provide compelling evidence for genetic homogeneity among families of mixed European and French-Canadian origin. In contrast, results excluded Greither's disease from the established erythrokeratodermia variabilis gene region indicating genetic heterogeneity of erythrokeratodermias. Based on recombinations, two genes assigned to 1p34-p35 were excluded: cartilage matrix protein and avian myelocytosis viral oncogene. Connexin-37 (GJA4), a member of the connexin gene family, maps within the erythrokeratodermia variabilis region and is an attractive candidate gene. Direct sequencing of the coding region of GJA4 in four patients revealed several variations, including a novel polymorphism within the 5' cytoplasmic domain, but no pathogenic mutations were found, thus excluding Connexin-37 as a candidate. There is evidence, however, that other epidermally expressed connexins cluster in this region, and one may yet be determined to play a role in the pathogenesis of erythrokeratodermia variabilis.

Autosomal recessive inheritance of erythrokeratoderma variabilis

Erythrokeratoderma variabilis is a rare genodermatosis conventionally regarded as autosomal dominant in inheritance. We describe the clinical features and light and electron microscopic findings in two affected siblings born to unaffected parents and suggest an autosomal recessive mode of inheritance in this family. We also briefly review the literature on this disorder.

The molecular pathology of progressive symmetric erythrokeratoderma: a frameshift mutation in the loricrin gene and perturbations in the cornified cell envelope

The erythrokeratodermas (EKs) are a group of disorders characterized by erythematous plaques associated with variable features that include palmoplantar keratoderma. One type of EK is known as "progressive symmetric erythrokeratoderma" (PSEK). We studied members of a family of Japanese origin in which the index case with PSEK had had well-demarcated nonmigratory erythematous plaques on her extremities since birth. Sequence determination of the loricrin gene revealed an insertion of a C following nucleotide 709. The mutation results in a frameshift that changes the terminal 91 amino acids in the wild-type polypeptide into missense amino acids and adds 65 additional residues. This further implicates loricrin defects in the pathogenesis of disorders with palmoplantar keratoderma and pseudoainhum.

Erythrokeratodermia variabilis present at birth: case report and review of the literature

A healthy boy had the distinctive lesions of erythrokeratodermia variabilis (EKV) at birth. Twenty-eight patients described in the literature had EKV that presented in childhood. Nine of the 28 were said to have had a rash since birth, but none were distinctive of EKV. To our knowledge this is the first well-documented case describing a child born with the skin manifestations of EKV. We conclude that patients with EKV are infrequently born with a rash, and that only very rarely when the rash is present is it suggestive of the disorder.

Histological and ultrastructural study of a family with erythrokeratodermia progressiva symmetrica

We have examined a family with 4 members in three succeeding generations suffering from a severe keratinization disorder. The clinical phenotype, with symmetric plaques on the extremities, corresponded to erythrokeratodermia progressiva symmetrica. It was manifested at birth, however, and in addition to the hyperkeratotic plaques, follicular hyperkeratosis was also observed. Electron microscopy revealed multiple morphological changes such as myelinated membrane structures, or needles, which were similar to those occurring in ichthyotic disorders and tyrosinemia, as well as in harlequin fetuses, all of which were excluded clinically or biochemically in our patients.