Dyskeratosis congenita: a literature review

Reticulated pigmentary changes and Terry's nails in a patient with a TERT variant-associated telomere biology disorder

Telomere biology disorders (TBD) are a complex set of inherited illnesses characterized by short telomeres. Dyskeratosis congenita (DC), which is now considered a severe TBD phenotype, is characterized by reticulated pigmentary changes, nail dystrophy, premalignant oral leukoplakia, and systemic involvement. This case describes a 2-year-old female with reticulated pigmentary changes and Terry's nails who was found to have a TERT variant and short telomeres; she lacked other mucocutaneous and systemic features of TBD. This report describes a unique clinical presentation of TBD and highlights the importance of upholding suspicion for TBD in individuals with limited or subtle features of classic DC.

Mucosal Cancers Arising in Potentially Malignant Lesions of the Oral Mucosa Are Marjolin Ulcers: New Insights Into Old Concepts

INTRODUCTION

Several disparate mucocutaneous diseases present oral mucosal lesions that have been classically labeled as "pre-cancerous", "pre-malignant", or "potentially malignant". These include oral lichen planus, dyskeratosis congenita, tertiary syphilitic glossitis chronic graft-versus-host-disease, and oral discoid lupus erythematosus. There is much confusion in literature regarding the real malignant potential of these oral lesions in relation to the incidence of squamous cell carcinoma.

OBJECTIVES

We tried to unify the occurrence of squamous cell carcinoma in some oral mucosal diseases into the classic concept of "Marjolin ulcer".

METHODS

We analyzed the most relevant published evidence of the occurrence of squamous cell carcinoma arising in oral lichen planus, dyskeratosis congenita, tertiary syphilitic glossitis chronic graft-versus-host-disease, and oral discoid lupus erythematosus, and tried to establish a logical link between them.

RESULTS

Reported cases of squamous cell carcinoma occurring in oral lesions of these diseases seem to appear in old standing, scarring lesions.

CONCLUSIONS

Oral lichen planus, dyskeratosis congenita, tertiary syphilitic glossitis, chronic graft-versushost-disease, and oral discoid lupus erythematosus are not "pre-malignant diseases", their long-lasting mucosal scars are prone to the development of squamous cell carcinomas. In this sense, this tumor can be considered a mucosal type of Marjolin ulcer.

Emerging concepts involving inhibitory and activating RNA functionalization towards the understanding of microcephaly phenotypes and brain diseases in humans

Microcephaly is characterized as a small head circumference, and is often accompanied by developmental disorders. Several candidate risk genes for this disease have been described, and mutations in non-coding regions are occasionally found in patients with microcephaly. Various non-coding RNAs (ncRNAs), such as microRNAs (miRNAs), SINEUPs, telomerase RNA component (TERC), and promoter-associated lncRNAs (pancRNAs) are now being characterized. These ncRNAs regulate gene expression, enzyme activity, telomere length, and chromatin structure through RNA binding proteins (RBPs)-RNA interaction. Elucidating the potential roles of ncRNA-protein coordination in microcephaly pathogenesis might contribute to its prevention or recovery. Here, we introduce several syndromes whose clinical features include microcephaly. In particular, we focus on syndromes for which ncRNAs or genes that interact with ncRNAs may play roles. We discuss the possibility that the huge ncRNA field will provide possible new therapeutic approaches for microcephaly and also reveal clues about the factors enabling the evolutionary acquisition of the human-specific "large brain."

Case report: A novel mutation in RTEL1 gene in dyskeratosis congenita

Dyskeratosis congenita (DKC), also known as Zinsser-Cole-Engman syndrome, is a telomeropathy typically presenting as a triad of leukoplakia, nail dystrophy, and reticular hyperpigmentation. Reported genetic mutations linked to DKC include DKC1, TINF2, TERC, TERT, C16orf57, NOLA2, NOLA3, WRAP53/TCAB1, and RTEL1. Homozygous, compound heterozygous, and heterozygous mutations in RTEL1 (RTEL1, regulator of telomere elongation helicase 1) gene on chromosome 20q13 are known to cause autosomal dominant as well as recessive DKC. Pathogenic variants of RTEL1 gene in DKC patients include c.2288G>T (p. Gly763Val), c.3791G>A (p. Arg1264His), and RTEL p. Arg981Trp. We report a novel homozygous variant of RTEL1, transcript ID: ENST00000360203.11, exon 24, c.2060C>T (p.Ala687Val), in a patient of DKC presenting with leukoplakia, dystrophic nails, reticulate pigmentation, and positive family history of a similar phenotype. The novel variant, reported as a variant of uncertain significance, may therefore be considered diagnostic for DKC in a Pakistani population.

Severe immunochemotherapy-induced toxicities in a patient with dyskeratosis congenita and literature review

OBJECTIVES

Dyskeratosis congenita (DC) is a rare inherited disease characterized by the triad of reticulate hyperpigmentation, nail dystrophy and oral leukoplakia. DC patients are considered vulnerable to external pressure, such as immunochemotherapy. There are very few cases reporting severe therapy-induced toxicities in patients with DC.

METHODS

A 27-year-old woman was admitted to our hospital with a 4-month history of pancytopenia and a 7-day history of dyspnea with coughing. She was diagnosed with non-Hodgkin's lymphoma 5 months ago. She received immunochemotherapy due to non-Hodgkin's lymphoma but experienced recurrent fever, oral ulcer, pancytopenia, dyspnea and other symptoms during immunochemotherapy. On admission, she experienced an aggravation of respiratory symptoms, recurrent infections and acute heart failure.

RESULTS

Laboratory examination confirmed pancytopenia, and chest computed tomography showed interstitial lung disease (ILD). Genetic analysis results confirmed the presence of DC and a TINF2 gene mutation. With continuous supportive and anti-infection treatment, her condition finally stabilized. She was discharged from the hospital after nearly 2 months.

DISCUSSION

We reviewed similar cases and found common features that could be useful. However, the reported cases are very limited. More cases and studies are needed.

CONCLUSION

These cases indicate that DC patients seem more vulnerable to therapy toxicities; thus, physicians should be careful when treating these patients with chemotherapy drugs or radiation therapy. Reduced-intensity therapy may be considered.

Novel TINF2 gene mutation in dyskeratosis congenita with extremely short telomeres: A case report

BACKGROUND

Dyskeratosis congenita is a rare disease characterized by bone marrow failure and a clinical triad of oral leukoplakia, nail dystrophy, and abnormal skin pigmentation. The genetics of dyskeratosis congenita include mutations in genes involved in telomere maintenance, including TINF2.

CASE SUMMARY

Here, we report a female patient who presented thrombocytopenia, anemia, reticulate hyperpigmentation, dystrophy in fingernails and toenails, and leukoplakia on the tongue. A histopathological study of the skin showed dyskeratocytes; however, a bone marrow biopsy revealed normal cell morphology. The patient was diagnosed with dyskeratosis congenita, but her family history did not reveal significant antecedents. Whole-exome sequencing showed a novel heterozygous punctual mutation in exon 6 from the TINF2 gene, namely, NM_001099274.1:c.854delp.(Val285Alafs*32). An analysis of telomere length showed short telomeres relative to the patient’s age.

CONCLUSION

The disease in this patient was caused by a germline novel mutation of TINF2 in one of her parents.

A Novel Variant and a Missense Variant Identified in the DKC1 Gene in Three Chinese Familieswith Dyskeratosis Congenita

Purpose

Dyskeratosis congenita (DC) is an inherited telomere biology disorder characterized clinically by mucocutaneous triad of reticulate hyperpigmentation, nail changes and oral leukoplakia. Bone marrow failure, pulmonary fibrosis and malignancies are the mainly life-threatening causes. There are X-linked recessive, autosomal dominant and autosomal recessive patterns of DC. DKC1 is the most common pathogenic mutation gene responsible for X-linked DC, and it encodes a protein, dyskerin, which is a component of telomerase holoenzyme complex essential for telomere maintenance. Patients with DC have very short telomeres, but the precise pathogenic mechanism remains unclear. This study aimed to identify the causative mutations in the DKC1 gene in three Chinese families with the X-linked form of DC.

Patients and Methods

Three Chinese families with DC were included in this study. Whole exome sequencing and Sanger sequencing were performed to clarify the mutation of DKC1 gene. Measurement of relative telomere length through qPCR. Predictions of protein structure and function were performed using bioinformatics tools, including I-TASSER, Polyphen-2 and SIFT.

Results

There were four males with DC and a female carrier in three Chinese pedigrees. The novel mutation c.92A>C (p. Q31P) and the missense mutation c.1058C>T (p. A353V) in DKC1 were identified. Both mutations locally changed the structure of dyskerin. Variant Q31P and A353V were predicted to have “deleterious” and “natural” effects on the function of dyskerin, respectively.

Conclusion

The novel variant and missense variant detected in the DKC1 gene improve our understanding of DC and broaden the mutation spectrum of the DKC1 gene.

Fanconi anemia and dyskeratosis congenita/telomere biology disorders: Two inherited bone marrow failure syndromes with genomic instability

Inherited bone marrow failure syndromes (IBMFS) are a complex and heterogeneous group of genetic diseases. To date, at least 13 IBMFS have been characterized. Their pathophysiology is associated with germline pathogenic variants in genes that affect hematopoiesis. A couple of these diseases also have genomic instability, Fanconi anemia due to DNA damage repair deficiency and dyskeratosis congenita/telomere biology disorders as a result of an alteration in telomere maintenance. Patients can have extramedullary manifestations, including cancer and functional or structural physical abnormalities. Furthermore, the phenotypic spectrum varies from cryptic features to patients with significantly evident manifestations. These diseases require a high index of suspicion and should be considered in any patient with abnormal hematopoiesis, even if extramedullary manifestations are not evident. This review describes the disrupted cellular processes that lead to the affected maintenance of the genome structure, contrasting the dysmorphological and oncological phenotypes of Fanconi anemia and dyskeratosis congenita/telomere biology disorders. Through a dysmorphological analysis, we describe the phenotypic features that allow to make the differential diagnosis and the early identification of patients, even before the onset of hematological or oncological manifestations. From the oncological perspective, we analyzed the spectrum and risks of cancers in patients and carriers.

Genetic Disorders with Predisposition to Paediatric Haematopoietic Malignancies—A Review

The view of paediatric cancer as a genetic disease arises as genetic research develops. Germline mutations in cancer predisposition genes have been identified in about 10% of children. Paediatric cancers are characterized by heterogeneity in the types of genetic alterations that drive tumourigenesis. Interactions between germline and somatic mutations are a key determinant of cancer development. In 40% of patients, the family history does not predict the presence of inherited cancer predisposition syndromes and many cases go undetected. Paediatricians should be aware of specific symptoms, which highlight the need of evaluation for cancer syndromes. The quickest possible identification of such syndromes is of key importance, due to the possibility of early detection of neoplasms, followed by presymptomatic genetic testing of relatives, implementation of appropriate clinical procedures (e.g., avoiding radiotherapy), prophylactic surgical resection of organs at risk, or searching for donors of hematopoietic stem cells. Targetable driver mutations and corresponding signalling pathways provide a novel precision medicine strategy.Therefore, there is a need for multi-disciplinary cooperation between a paediatrician, an oncologist, a geneticist, and a psychologist during the surveillance of families with an increased cancer risk. This review aimed to emphasize the role of cancer-predisposition gene diagnostics in the genetic surveillance and medical care in paediatric oncology.

A New Pathogenic Variant of the RTEL1 Gene and Dyskeratosis Congenita: A Dermatological View

Abstract is missing (Short communication)

Multisystemic Manifestations in Rare Diseases: The Experience of Dyskeratosis Congenita

Dyskeratosis congenital (DC) is the first genetic syndrome described among telomeropathies. Its classical phenotype is characterized by the mucocutaneous triad of reticulated pigmentation of skin lace, nail dystrophy and oral leukoplakia. The clinical presentation, however, is heterogeneous and serious clinical complications include bone marrow failure, hematological and solid tumors. It may also involve immunodeficiencies, dental, pulmonary and liver disorders, and other minor complication. Dyskeratosis congenita shows marked genetic heterogeneity, as at least 14 genes are responsible for the shortening of telomeres characteristic of this disease. This review discusses clinical characteristics, molecular genetics, disease evolution, available therapeutic options and differential diagnosis of dyskeratosis congenita to provide an interdisciplinary and personalized medical assessment that includes family genetic counseling.

Case Report: A Missense Mutation in Dyskeratosis Congenita 1 Leads to a Benign Form of Dyskeratosis Congenita Syndrome With the Mucocutaneous Triad

BACKGROUND

Dyskeratosis congenita (DC) is a rare inheritable disorder characterized by bone marrow failure and mucocutaneous triad (reticular skin pigmentation, nail dystrophy, and oral leukoplakia). Dyskeratosis congenita 1 (DKC1) is responsible for 4.6% of the DC with an X-linked inheritance pattern. Almost 70 DKC1 variations causing DC have been reported in the Human Gene Mutation Database.

RESULTS

Here we described a 14-year-old boy in a Chinese family with a phenotype of abnormal skin pigmentation on the neck, oral leukoplakia, and nail dysplasia in his hands and feet. Genetic analysis and sequencing revealed hemizygosity for a recurrent missense mutation c.1156G > A (p.Ala386Thr) in DKC1 gene. The heterozygous mutation (c.1156G > A) from his mother and wild-type sequence from his father were obtained in the same site of DKC1. This mutation was determined as disease causing based on silico software, but the pathological phenotypes of the proband were milder than previously reported at this position (HGMDCM060959). Homology modeling revealed that the altered amino acid was located near the PUA domain, which might affect the affinity for RNA binding.

CONCLUSION

This DKC1 mutation (c.1156G > A, p.Ala386Thr) was first reported in a Chinese family with mucocutaneous triad phenotype. Our study reveals the pathogenesis of DKC1 c.1156G > A mutation to DC with a benign phenotype, which expands the disease variation database, the understanding of genotype-phenotype correlations, and facilitates the clinical diagnosis of DC in China.

Mutations Involved in Premature-Ageing Syndromes

Premature-ageing syndromes are a heterogeneous group of rare genetic disorders resembling features of accelerated ageing and resulting from mutations in genes coding for proteins required for nuclear lamina architecture, DNA repair and maintenance of genome stability, mitochondrial function and other cellular processes. Hutchinson–Gilford progeria syndrome (HGPS) and Werner syndrome (WS) are two of the best-characterized progeroid syndromes referred to as childhood- and adulthood-progeria, respectively. This article provides an updated overview of the mutations leading to HGPS, WS, and to the spectrum of premature-ageing laminopathies ranging in severity from congenital restrictive dermopathy (RD) to adult-onset atypical WS, including RD-like laminopathies, typical and atypical HGPS, more and less severe forms of mandibuloacral dysplasia (MAD), Néstor-Guillermo progeria syndrome (NGPS), atypical WS, and atypical progeroid syndromes resembling features of HGPS and/or MAD but resulting from impaired DNA repair or mitochondrial functions, including mandibular hypoplasia, deafness, progeroid features, and lipodystrophy (MDPL) syndrome and mandibuloacral dysplasia associated to MTX2 (MADaM). The overlapping signs and symptoms among different premature-ageing syndromes, resulting from both a large genetic heterogeneity and shared pathological pathways underlying these conditions, require an expert clinical evaluation in specialized centers paralleled by next-generation sequencing of panels of genes involved in these disorders in order to establish as early as possible an accurate clinical and molecular diagnosis for a proper patient management.

Multiple bilateral hip fractures in a patient with dyskeratosis congenita caused by a novel mutation in the PARN gene

We report a case of a young male patient with clinical signs of dyskeratosis congenita who presented with multiple bilateral low-traumatic hip fractures. Whole exome sequencing (WES) showed a previously unreported mutation in the poly(A)-specific ribonuclease (PARN) gene. Zoledronic acid 5 mg over 3 years was effective at preventing further fractures. A male patient was referred to our clinic at age 24 due to multiple bilateral hip fractures. At the time of admission, the patient's height was 160 cm and weight 40 kg; bone mineral density (BMD) at the lumbar spine was normal (L1-L4 0.0 Z-score). The patient was found to have abnormal skin pigmentation, hyperkeratosis of palms and soles, nail dystrophy, and signs of bone marrow failure (BMF). Bone fragility first presented at 5 years old with a wrist fracture, followed by multiple bilateral low-traumatic hip fractures without falls from 14 to 24 years. WES showed a previously unreported mutation (NM_002582.3: c.1652delA; p.His551fs) in the poly(A)-specific ribonuclease (PARN) gene. Flow fish telomere measurement result was 5.9 (reference range 8.0-12.6), which is consistent with the DC diagnosis. Permanent fixation with internal metal rods and zoledronic acid 5 mg over 3 years was effective at preventing further fractures over 4 years of follow-up. Additionally, BMF did not progress over 4 years of observation. DC associated with PARN gene mutations might predispose to low-traumatic multiple hip fractures in adolescents and young adults. Treatment with zoledronic acid in this case was effective and safe at preventing further fractures.

CST in maintaining genome stability: Beyond telomeres

The human CST (CTC1-STN1-TEN1) complex is an RPA-like single-stranded DNA binding protein complex. While its telomeric functions have been well investigated, numerous studies have revealed that hCST also plays important roles in maintaining genome stability beyond telomeres. Here, we review and discuss recent discoveries on CST in various global genome maintenance pathways, including findings on the CST supercomplex structure, its functions in unperturbed DNA replication, stalled replication, double-strand break repair, and the ATR-CHK1 activation pathway. By summarizing these recent discoveries, we hope to offer new insights into genome maintenance mechanisms and the pathogenesis of CST mutation-associated diseases.

Skin Pigmentation Abnormalities and Their Possible Relationship with Skin Aging

Skin disorders showing abnormal pigmentation are often difficult to manage because of their uncertain etiology or pathogenesis. Abnormal pigmentation is a common symptom accompanying aging skin. The association between skin aging and skin pigmentation abnormalities can be attributed to certain inherited disorders characterized by premature aging and abnormal pigmentation in the skin and some therapeutic modalities effective for both. Several molecular mechanisms, including oxidative stress, mitochondrial DNA mutations, DNA damage, telomere shortening, hormonal changes, and autophagy impairment, have been identified as involved in skin aging. Although each of these skin aging-related mechanisms are interconnected, this review examined the role of each mechanism in skin hyperpigmentation or hypopigmentation to propose the possible association between skin aging and pigmentation abnormalities.