Refined localization of dyschromatosis symmetrica hereditaria gene to a 9.4-cM region at 1q21-22 and a literature review of 136 cases reported in China

Inherited Reticulate Pigmentary Disorders

Reticulate pigmentary disorders (RPDs) are a group of inherited and acquired skin conditions characterized by hyperpigmented and/or hypopigmented macules. Inherited RPDs include dyschromatosis symmetrica hereditaria (DSH), dyschromatosis universalis hereditaria (DUH), reticulate acropigmentation of Kitamura (RAK), Dowling-Degos disease (DDD), dyskeratosis congenita (DKC), Naegeli-Franceschetti-Jadassohn syndrome (NFJS), dermatopathia pigmentosa reticularis (DPR), and X-linked reticulate pigmentary disorder. Although reticulate pattern of pigmentation is a common characteristic of this spectrum of disorders, the distribution of pigmentation varies among these disorders, and there may be clinical manifestations beyond pigmentation. DSH, DUH, and RAK are mostly reported in East Asian ethnicities. DDD is more common in Caucasians, although it is also reported in Asian countries. Other RPDs show no racial predilection. This article reviews the clinical, histological, and genetic variations of inherited RPDs.

Clinical and Genetic Review of Hereditary Acral Reticulate Pigmentary Disorders

Reticulated pigmentation is a unique pigmentary change caused by a heterogeneous group of hereditary and acquired disorders. This pigmentation is characterized by a mottled appearance, with lesions that vary in size and pigmentary content. This review discusses the hereditary group of the reticulated pigmentation disorders, such as dyschromatosis symmetrica hereditaria, dyschromatosis universalis hereditaria, and reticulate acropigmentation of Kitamura. The clinical presentation and histopathological features often overlap, making diagnosis difficult. However, each of these hereditary conditions possesses a unique genetic mutation, and genetic analysis is thus more useful in the diagnosis of these conditions. This article delivers an update regarding the clinical features, detailed histopathological description, and genetic information concerning hereditary reticulate pigmentary disorders and aims to provide useful background for use by clinical dermatologists and histopathologists when approaching this group of hereditary disorders.

Dyschromatosis symmetrica hereditaria with cutaneous lupus erythematosus and hyperthyroidism

Dyschromatosis symmetrica hereditaria (DSH) is a rare genodermatosis characterized by various sizes of both hyper- and hypopigmented macules arranged in reticulated patterns on the face and the dorsal aspects of the extremities. There are also cutaneous and extracutaneous abnormalities, but they are rare. As far as we know, DSH associated with immune-mediated conditions has not been reported. We report the first case of DSH, which is associated with cutaneous lupus erythematosus and hyperthyroidism.

Differential Diagnosis of Two Chinese Families with Dyschromatoses by Targeted Gene Sequencing

Background:

The dyschromatoses are a group of disorders characterized by simultaneous hyperpigmented macules together with hypopigmented macules. Dyschromatosis universalis hereditaria (DUH) and dyschromatosis symmetrica hereditaria are two major types. While clinical and histological presentations are similar in these two diseases, genetic diagnosis is critical in the differential diagnosis of these entities.

Methods:

Three patients initially diagnosed with DUH were included. The gene test was carried out by targeted gene sequencing. All mutations detected on ADAR1 and ABCB6 genes were analyzed according to the frequency in control database, the mutation types, and the published evidence to determine the pathogenicity.

Results:

Family pedigree and clinical presentations were reported in 3 patients from two Chinese families. All patients have prominent cutaneous dyschromatoses involving the whole body without systemic complications. Different pathogenic genes in these patients with similar phenotype were identified: One novel mutation on ADAR1 (c. 1325C>G) and one recurrent mutation in ABCB6 (c. 1270T>C), which successfully distinguished two diseases with the similar phenotype.

Conclusion:

Targeted gene sequencing is an effective tool for genetic diagnosis in pigmentary skin diseases.

Adenosine deaminases acting on RNA, RNA editing, and interferon action

Adenosine deaminases acting on RNA (ADARs) catalyze adenosine (A) to inosine (I) editing of RNA that possesses double-stranded (ds) structure. A-to-I RNA editing results in nucleotide substitution, because I is recognized as G instead of A both by ribosomes and by RNA polymerases. A-to-I substitution can also cause dsRNA destabilization, as I:U mismatch base pairs are less stable than A:U base pairs. Three mammalian ADAR genes are known, of which two encode active deaminases (ADAR1 and ADAR2). Alternative promoters together with alternative splicing give rise to two protein size forms of ADAR1: an interferon-inducible ADAR1-p150 deaminase that binds dsRNA and Z-DNA, and a constitutively expressed ADAR1-p110 deaminase. ADAR2, like ADAR1-p110, is constitutively expressed and binds dsRNA. A-to-I editing occurs with both viral and cellular RNAs, and affects a broad range of biological processes. These include virus growth and persistence, apoptosis and embryogenesis, neurotransmitter receptor and ion channel function, pancreatic cell function, and post-transcriptional gene regulation by microRNAs. Biochemical processes that provide a framework for understanding the physiologic changes following ADAR-catalyzed A-to-I ( = G) editing events include mRNA translation by changing codons and hence the amino acid sequence of proteins; pre-mRNA splicing by altering splice site recognition sequences; RNA stability by changing sequences involved in nuclease recognition; genetic stability in the case of RNA virus genomes by changing sequences during viral RNA replication; and RNA-structure-dependent activities such as microRNA production or targeting or protein-RNA interactions.

Generalized Dowling-Degos disease

BACKGROUND

Dowling-Degos disease (DDD) is a rare inherited disease characterized by reticular hyperpigmentation on flexor surfaces.

OBJECTIVE

We sought to describe several cases of generalized DDD, a presentation that resemble dyschromatosis universalis hereditaria.

METHODS

The clinical manifestations, histopathologic, and genetic studies of a family with autosomal dominant inheritance were analyzed.

RESULTS

The father and his sister had reticular hyperpigmentation on flexor surfaces, whereas the daughter and son had generalized hyperpigmentation with numerous hypopigmented or erythematous macules and papules on the trunk and limbs. Skin biopsy specimens from both types of lesions all had typical features of DDD. Biopsy specimens from axillary skin had features of Galli-Galli disease, an acantholytic form. There were no mutations of the double-stranded RNA-specific adenosine deaminase or keratin 5 genes.

LIMITATION

Generalizations cannot be drawn from genetic study of only one family.

CONCLUSION

DDD can present with generalized hyperpigmentation and hypopigmented papules.

Identification of a novel ADAR mutation in a Chinese family with dyschromatosis symmetrica hereditaria (DSH)

Dyschromatosis symmetrica hereditaria (DSH [MIM 127400]) is characterized by the presence of hyperpigmented and hypopigmented macules mostly on the dorsal aspects of the extremities. Genetic studies have identified mutations in the ADAR gene, encoding double-stranded RNA-specific adenosine deaminase, to be responsible for this disorder. Here, we found a novel deletion mutation in the ADAR gene, 2929delA, in a Chinese family with DSH. This mutation is located in codon 977 (AGC-->GC), and leads to a frameshift and truncated protein of 250 amino acids with 76 novel amino acids prior to a premature stop codon. The truncated ADAR is predicted to lack the ADEAMc (tRNA-specific and double-stranded RNA adenosine deaminase) domain. This study should be useful for genetic counseling and prenatal diagnosis for affected families and in expanding the database on ADAR gene mutations in DSH.

Mutation Analysis of the ADAR1 Gene in Dyschromatosis Symmetrica Hereditaria and Genetic Differentiation from both Dyschromatosis Universalis Hereditaria and Acropigmentatio Reticularis

Dyschromatosis symmetrica hereditaria (DSH) (also called "reticulate acropigmentation of Dohi") is a pigmentary genodermatosis of autosomal dominant inheritance. We have clarified for the first time four pathological mutations of the double-stranded RNA-specific adenosine deaminase gene (ADAR1 or DSRAD) in four DSH pedigrees. In this paper, we report 16 novel mutations containing six missense substitutions (p.V906F, p.K1003R, p.G1007R, p.C1036S, p.S1064F, p.R1078C), two splice site mutations (IVS2+2T>G, IVS8+2T>A), six frameshift mutations (p.H216fs, p.K433fs, p.G507fs, p.P727fs, p.V955fs, p.K1201fs), and two nonsense mutations (p.R426X, p.Q600X) found in Japanese patients with DSH. We did not establish any clear correlation between the clinical phenotypes and the genotypes of ADAR1 gene mutations in our examination of 16 cases plus four pedigrees. None of the different mutations identified in our studies of 20 cases suggested any founder effect. Furthermore, we did not identify any mutations in the ADAR1 gene of three patients with dyschromatosis universalis hereditaria or three patients with acropigmentatio reticularis, indicating that the two diseases are completely different from DSH, although they have sometimes been suggested to be phenotypical variations of DSH.

Identification of a novel mutation in the DSRAD gene in a Chinese pedigree with dyschromatosis symmetrica hereditaria

Dyschromatosis symmetrica hereditaria (DSH) is an autosomal dominant skin disorder characterized by a mixture of hyperpigmented and hypopigmented macules distributed on the face and dorsal aspects of the extremities that appear in infancy or early childhood. The DSH locus has recently been mapped to chromosome 1q21 and then pathogenic mutations have been identified in the DSRAD gene. In the study reported here we examined the DSRAD gene mutations of a three-generation Chinese pedigree with DSH by direct sequencing. We identified a novel heterozygous nucleotide T-->C transition at position 3388 in exon 14 of the DSRAD gene which induces a C1130R change in the putative deaminase domain of DSRAD. Our study expands the database on the DSRAD gene mutations in DSH and enriches the knowledge about the function of the DSRAD gene.