Bilateral retinopathy, aplastic anaemia, and central nervous system abnormalities: a new syndrome?

TYMS-ENOSF1 Dyskeratosis Congenita in a Patient With Ring Chromosome 18: A Case Report

Dyskeratosis Congenita (DC) is a rare genetic syndrome due to variants in genes involved in telomeric regulation and maintenance, impacting multiple organ systems. We report a case of DC secondary to TYMS gene deletion in a patient with ring chromosome 18 and related partial monosomy 18p and 18q. TYMS encodes thymidylate synthase, and compound heterozygosity for loss of function variants in TYMS and a specific haplotype of its antisense regulator ENOSFI (enolase super family 1) causes digenic DC. The patient had physical and developmental features of 18p monosomy, including poor growth, feeding issues, distinctive facial features, and strabismus. In early infancy, he developed diffuse hyperpigmentation as well as numerous punctate hypopigmented macules, sparse hair, and nail dystrophy, and diagnosis of DC was confirmed with a telomere length assay. Our case highlights that individuals with deletions at 18p encompassing TYMS should be evaluated for features of digenic dyskeratosis congenita.

Adult-Onset Presentations of Retinopathy Associated With Short Telomere Syndromes

Purpose: To describe the association between short telomere syndrome and exudative retinopathies in adults. Methods: This case series compared the presentation, course of treatment, and visual outcomes of 2 patients with adult-onset retinopathy associated with short telomere syndrome. Results: In Case 1, a 53-year-old man initially presented with bilateral retinal telangiectasias and preretinal hemorrhage in the left eye, which was followed by multiple vitreous hemorrhages. In the subsequent 15 years, the patient was diagnosed with pulmonary fibrosis, liver cirrhosis, and a RTEL1 gene mutation, consistent with short telomere syndrome. In Case 2, a previously asymptomatic 26-year-old man with paternally inherited short telomere syndrome (TERC gene mutation) presented with floaters, bilateral peripheral retinal capillary nonperfusion, and an aneurysmal lesion with surrounding exudation. Conclusions: Short telomere syndromes, with systemic features that can be life-threatening, can manifest initially in adulthood with retinal telangiectasia, aneurysmal lesions, exudation, or peripheral retinal capillary nonperfusion, preceding systemic manifestations. Because the systemic manifestations of retinal telangiectasia and peripheral retinal capillary nonperfusion are progressive and can be life-threatening, recognizing these findings in adults with retinal telangiectasia is crucial.

Different phenotypes with different endings-Telomere biology disorders and cancer predisposition with long telomeres

Rare germline pathogenic variants (GPVs) in genes essential in telomere length maintenance and function have been implicated in two broad classes of human disease. The telomere biology disorders (TBDs) are a spectrum of life-threatening conditions, including bone marrow failure, liver and lung disease, cancer and other complications caused by GPVs in telomere maintenance genes that result in short and/or dysfunctional telomeres and reduced cellular replicative capacity. In contrast, cancer predisposition with long telomeres (CPLT) is a disorder associated with elevated risk of a variety of cancers, primarily melanoma, thyroid cancer, sarcoma, glioma and lymphoproliferative neoplasms caused by GPVs in shelterin complex genes that lead to excessive telomere elongation and increased cellular replicative capacity. While telomeres are at the root of both disorders, the term TBD is used to convey the clinical phenotypes driven by critically short or otherwise dysfunctional telomeres and their biological consequences.

Inherited bone marrow failure syndromes and germline predisposition to myeloid neoplasia: A practical approach for the pathologist

The diagnostic work up and surveillance of germline disorders of bone marrow failure and predisposition to myeloid malignancy is complex and involves correlation between clinical findings, laboratory and genetic studies, and bone marrow histopathology. The rarity of these disorders and the overlap of clinical and pathologic features between primary and secondary causes of bone marrow failure, acquired aplastic anemia, and myelodysplastic syndrome may result in diagnostic uncertainty. With an emphasis on the pathologist's perspective, we review diagnostically useful features of germline disorders including Fanconi anemia, Shwachman-Diamond syndrome, telomere biology disorders, severe congenital neutropenia, GATA2 deficiency, SAMD9/SAMD9L diseases, Diamond-Blackfan anemia, and acquired aplastic anemia. We discuss the distinction between baseline morphologic and genetic findings of these disorders and features that raise concern for the development of myelodysplastic syndrome.

Dyskeratosis congenita: natural history of the disease through the study of a cohort of patients diagnosed in childhood

Background

Dyskeratosis congenita (DC) is a multisystem and ultra-rare hereditary disease characterized by somatic involvement, bone marrow failure, and predisposition to cancer. The main objective of this study is to describe the natural history of DC through a cohort of patients diagnosed in childhood and followed up for a long period of time.

Material and methods

Multicenter, retrospective, longitudinal study conducted in patients followed up to 24 years since being diagnosed in childhood (between 1998 and 2020).

Results

Fourteen patients were diagnosed with DC between the ages of 3 and 17 years (median, 8.5 years). They all had hematologic manifestations at diagnosis, and nine developed mucocutaneous manifestations during the first decade of life. Seven presented severe DC variants. All developed non-hematologic manifestations during follow-up. Mutations were identified in 12 patients. Thirteen progressed to bone marrow failure at a median age of 8 years [range, 3-18 years], and eight received a hematopoietic stem cell transplant. Median follow-up time was 9 years [range, 2-24 years]. Six patients died, the median age was 13 years [range, 6-24 years]. As of November 2022, eight patients were still alive, with a median age of 18 years [range, 6-32 years]. None of them have developed myeloblastic syndrome or cancer.

Conclusions

DC was associated with high morbidity and mortality in our series. Hematologic manifestations appeared early and consistently. Non-hematologic manifestations developed progressively. No patient developed cancer possibly due to their young age. Due to the complexity of the disease multidisciplinary follow-up and adequate transition to adult care are essential.

Spectrum of Liver Pathology in Dyskeratosis Congenita

Dyskeratosis congenita (DC) is a rare multisystemic disorder associated with defective telomere maintenance. Frequent clinical manifestations of DC include reticular skin pigmentation, dystrophic nails, oral leukoplakia, and bone marrow failure. Hepatic disturbances are reported to occur in 7% of DC patients. This study aimed to evaluate the histopathologic spectrum of hepatic involvement in this disorder. DC patients with liver tissue in the pathology database at Boston Children's Hospital from 1995 to 2022 were identified. Clinical and pathologic information was documented. Thirteen specimens from 11 DC patients were included (M:F = 7:4; median age at the time of liver tissue evaluation: 18 y). DC-associated gene mutations were identified in 9 patients; TERF1-interacting nuclear factor 2 ( TINF2) was the most frequently represented gene mutation, seen in 4 patients. All patients had bone marrow failure, whereas dystrophic nails, cutaneous abnormal pigmentation, and oral leukoplakia were noted in 73%, 64%, and 55% of patients, respectively. Seven patients underwent bone marrow transplants before biopsy/autopsy (median interval of 45 mo). Histologically, 3 of 4 patients who presented with portal hypertension showed noncirrhotic changes (nodular regenerative hyperplasia and/or obliterative portal venopathy), whereas prominent central and sinusoidal fibrosis was noted in patients with intrahepatic shunting and those showing features of chronic passive congestion. All cases showed hepatocyte anisonucleosis. One patient developed hepatic angiosarcoma, and another 1 had colorectal adenocarcinoma metastatic to the liver. DC patients show heterogeneous histologic findings in their liver. The findings of noncirrhotic portal hypertension, intrahepatic shunting, and angiosarcoma suggest vascular functional/structural pathology as a possible unifying etiology of hepatic manifestations of DC.

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.

Avascular Peripheral Retina in Infants

Avascular peripheral retina in an infant is a common characteristic of numerous pediatric retinal vascular disorders and often presents a diagnostic challenge to the clinician. In this review, key features of each disease in the differential diagnosis, from retinopathy of prematurity, familial exudative vitreoretinopathy, Coats disease, incontinentia pigmenti, Norrie disease, and persistent fetal vasculature, to other rare hematologic conditions and telomere disorders, will be discussed by expert ophthalmologists in the field.

The biology and management of dyskeratosis congenita and related disorders of telomeres

BACKGROUND

Dyskeratosis congenita (DC) is a multisystem syndrome characterized by mucocutaneous abnormalities, bone marrow failure, and predisposition to cancer. Studies over the last 25 years have led to the identification of 18 disease genes. These have a principal role in telomere maintenance, and patients usually have very short/abnormal telomeres. The advances have also led to the unification of DC with a number of other diseases, now collectively referred to as the telomeropathies or telomere biology disorders.

WHAT IS COVERED

Clinical features, genetics, and biology of the different subtypes. Expert view on diagnosis, treatment of the hematological complications and future.

EXPERT VIEW

As these are very pleotropic disorders affecting multiple organs, a high index of suspicion is necessary to make the diagnosis. Telomere length measurement and genetic analysis of the disease genes have become useful diagnostic tools. Although hematological defects can respond to danazol/oxymetholone, the only current curative treatment for these is hematopoietic stem cell transplantation (HSCT) using fludarabine-based conditioning protocols. New therapies are needed where danazol/oxymetholone is ineffective and HSCT is not feasible.

The Masquerading Retinopathy of Revesz Syndrome

Revesz syndrome is a rare telomeropathy characterized by bone marrow failure and exudative retinopathy. We report the case of a 2-year-old male child, initially treated with bilateral laser photocoagulation for retinopathy of prematurity. He developed exudative changes in the right eye, presumed to be Coats disease. Later, the left eye developed a total vitreous hemorrhage. Proliferative retinopathy was noted intraoperatively. Systemic features of bone marrow failure, growth retardation, and nail pigmentation were present. Genetic testing confirmed the diagnosis of Revesz syndrome. We describe our approach to diagnosis and surgical management of the case. [Ophthalmic Surg Lasers Imaging Retina 2022;53(6): 346-348.].

Functional interaction between compound heterozygous TERT mutations causes severe telomere biology disorder

Telomere biology disorders (TBDs) are a spectrum of multisystem inherited disorders characterized by bone marrow failure, resulting from mutations in genes encoding telomerase or other proteins involved in maintaining telomere length and integrity. Pathogenicity of variants in these genes can be hard to evaluate, since TBD mutations show highly variable penetrance and genetic anticipation due to inheritance of shorter telomeres with each generation. Thus, detailed functional analysis of newly identified variants is often essential. Here we describe a patient with compound heterozygous variants in the TERT gene, which encodes the catalytic subunit of telomerase, hTERT; this patient has the extremely severe Hoyeraal-Hreidarsson form of TBD, although his heterozygous parents are clinically unaffected. Molecular dynamic modeling and detailed biochemical analyses demonstrate that 1 allele (L557P) affects association of hTERT with its cognate RNA component hTR, while the other (K1050E) affects the binding of telomerase to its DNA substrate and enzyme processivity. Unexpectedly, the data demonstrate a functional interaction between the proteins encoded by the 2 alleles, with WT hTERT able to rescue the effect of K1050E on processivity, whereas L557P hTERT cannot. These data contribute to the mechanistic understanding of telomerase, indicating that RNA binding in 1 hTERT molecule affects the processivity of telomere addition by the other molecule. This work emphasizes the importance of functional characterization of TERT variants to reach a definitive molecular diagnosis for TBD patients, and in particular it illustrates the importance of analyzing the effects of compound heterozygous variants in combination to reveal interallelic effects.

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.

Revesz syndrome with bilateral retinal detachments successfully treated by pars plana vitrectomy

Background

Revesz syndrome is a rare type of the dyskeratosis congenita spectrum disorder that is characterized by nail dystrophy, oral leukoplakia, and abnormal skin pigmentation. The retinal features are similar to those of exudative retinopathy with avascular areas of the peripheral retina. There are only a few publications describing patients with Revesz syndrome who underwent ocular treatments for the retinal complications. We report a Case of Revesz syndrome with bilateral retinal detachments that were successfully reattached by pars plana vitrectomy.

Observations

A 3-year-old Japanese girl with Revesz Syndrome had progressive vitreal hemorrhages and tractional retinal detachments in both eyes. She underwent pars plana vitrectomy with lensectomy on both eyes. A retinal attachment with vision improvement was achieved by a single surgery for the right eye and after repeated surgeries for the left eye. Postoperative electroretinographic (ERG) examinations of the right eye showed a negative type ERG with the b-wave/a-wave ratio <1.0. There were extensive areas of avascular retina detected by fluorescein angiography and a thinning of the inner and outer retina detected by optical coherence tomography.

Conclusion and importance

Pars plana vitrectomy can effectively treat the extensive retinal detachment in an eye with Revesz syndrome. However, postoperative retinal ischemia can be detected by careful imaging.

Retinal Features of Family Members With Familial Exudative Vitreoretinopathy Caused By Mutations in KIF11 Gene

Purpose

To determine the clinical characteristics of patients and family members with familial exudative vitreoretinopathy (FEVR) caused by mutations in the KIF11 gene.

Methods

Twenty-one patients from 10 FEVR families with mutations in the KIF11 gene were studied. The retinal and systemic features were examined. The genetic analyses performed included Sanger sequencing of the KIF11 gene, whole exome sequencing, as well as array comparative genomic hybridization (CGH) analysis and multiple ligation probe assay (MLPA).

Results

Sequence analysis revealed seven different KIF11 mutations. Array CGH with MLPA revealed two different exon deletions. All probands had advanced FEVR with retinal detachments (RDs) and microcephaly with or without developmental disabilities. Patients with bilateral RDs were more frequently associated with developmental disabilities (P = 0.023). Multimodal imaging of the family members revealed that six of nine patients without RDs (66%) had varying degrees of chorioretinopathy. The retinal folds in FEVR patients were associated with severe retinal avascularization. However, funduscopic changes in the peripheral retina were unremarkable in family members without RDs. A score representing the peripheral vascular anomalies determined from the fluorescein angiograms was lower than that of control eyes of patients with mutations of the Wnt signaling genes (P = 0.0029).

Conclusions

The probands with KIF11 mutations were associated with severe ocular and systemic pathologies, whereas affected family members showed highly variable clinical manifestations. Peripheral vascular anomalies can often be unremarkable in eyes without RDs.

Translational Relevance

These findings highlight more diverse mechanisms that underlie the pathological changes in patients with FEVR.

Revesz syndrome revisited

Background

Revesz syndrome (RS) is an extremely rare variant of dyskeratosis congenita (DKC) with only anecdotal reports in the literature.

Methods

To further characterize the typical features and natural course of the disease, we screened the English literature and summarized the clinical and epidemiological features of previously published RS cases. In addition, we herein describe the first recorded patient in central Europe.

Results

The literature review included 18 children. Clinical features are summarized, indicating a low prevalence of the classical DKC triad. All patients experienced early bone marrow failure, in most cases within the second year of life (median age 1.5 years; 95% CI 1.4–1.6). Retinopathy occurred typically between 6 and 18 months of age (median age 1.1 years; 95% CI 0.7–1.5). The incidence of seizures was low and was present in an estimated 20% of patients. The onset of seizures was exclusively during early childhood. The Kaplan–Meier estimate of survival was dismal (median survival 6.5 years; 95% CI 3.6–9.4), and none of the patients survived beyond the age of 12 years. Stem cell transplantation (SCT) was performed in eight children, and after a median of 22 months from SCT four of these patients were alive at the last follow up visit.

Conclusion

RS is a severe variant of DKC with early bone marrow failure and retinopathy in all patients. Survival is dismal, but stem cell transplantation may be performed successfully and might improve prognosis in the future.

Intracranial calcifications in childhood: Part 2

This article is the second of a two-part series on intracranial calcification in childhood. In Part 1, the authors discussed the main differences between physiological and pathological intracranial calcification. They also outlined histological intracranial calcification characteristics and how these can be detected across different neuroimaging modalities. Part 1 emphasized the importance of age at presentation and intracranial calcification location and proposed a comprehensive neuroimaging approach toward the differential diagnosis of the causes of intracranial calcification. Pathological intracranial calcification can be divided into infectious, congenital, endocrine/metabolic, vascular, and neoplastic. In Part 2, the chief focus is on discussing endocrine/metabolic, vascular, and neoplastic intracranial calcification etiologies of intracranial calcification. Endocrine/metabolic diseases causing intracranial calcification are mainly from parathyroid and thyroid dysfunction and inborn errors of metabolism, such as mitochondrial disorders (MELAS, or mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes; Kearns-Sayre; and Cockayne syndromes), interferonopathies (Aicardi-Goutières syndrome), and lysosomal disorders (Krabbe disease). Specific noninfectious causes of intracranial calcification that mimic TORCH (toxoplasmosis, other [syphilis, varicella-zoster, parvovirus B19], rubella, cytomegalovirus, and herpes) infections are known as pseudo-TORCH. Cavernous malformations, arteriovenous malformations, arteriovenous fistulas, and chronic venous hypertension are also known causes of intracranial calcification. Other vascular-related causes of intracranial calcification include early atherosclerosis presentation (children with risk factors such as hyperhomocysteinemia, familial hypercholesterolemia, and others), healed hematoma, radiotherapy treatment, old infarct, and disorders of the microvasculature such as COL4A1- and COL4A2-related diseases. Intracranial calcification is also seen in several pediatric brain tumors. Clinical and familial information such as age at presentation, maternal exposure to teratogens including viruses, and association with chromosomal abnormalities, pathogenic genes, and postnatal infections facilitates narrowing the differential diagnosis of the multiple causes of intracranial calcification.

Interstitial Lung Disease in Rare Congenital Syndromes

Diffuse or interstitial lung disease (DLD/ILD) comprises a diverse group of disorders that involve the pulmonary parenchyma. Its aetiology varies (which makes the diagnostic process difficult), but congenital diseases, including malformation syndromes or developmental disorders, constitute one of the causative factors. They are rare conditions, and thus their frequency is not high. However, considering the progress and increasing availability of genetic testing, detection of these rare syndromes may increase. The aim of this work is, therefore, to present the symptomatology of selected congenital syndromes with ILD, taking into account the genetic background.

A unique case of coats plus syndrome and dyskeratosis congenita in a patient with CTC1 mutations

Coats plus syndrome (CP) is a rare condition characterized by bilateral exudative retinal telangiectasias with associated systemic disorders primarily affecting the brain, bone and gastrointestinal tract due to a mutation in the CTC1 gene. CTC1 mutations are also known to cause dyskeratosis congenita (DC), which is an inherited bone marrow failure syndrome characterized by skin pigmentation abnormalities, nail dystrophy, and oral leukoplakia. This is the first reported case of a patient diagnosed with both CP and DC caused by compound heterozygous CTC1 gene mutations. Moreover, one of the variant mutations found in this patient has never been published before.

Prognostic significance of pulmonary function tests in dyskeratosis congenita, a telomere biology disorder

Pulmonary fibrosis and pulmonary arteriovenous malformations are known manifestations of dyskeratosis congenita (DC), a telomere biology disorder (TBD) and inherited bone marrow failure syndrome caused by germline mutations in telomere maintenance genes resulting in very short telomeres. Baseline pulmonary function tests (PFTs) and long-term clinical outcomes have not been thoroughly studied in DC/TBDs.

In this retrospective study, 43 patients with DC and 67 unaffected relatives underwent baseline PFTs and were followed for a median of 8 years (range 1–14). Logistic regression and competing risk models were used to compare PFT results in relation to clinical and genetic characteristics, and patient outcomes.

Restrictive abnormalities on spirometry and moderate-to-severe reduction in diffusing capacity of the lung for carbon monoxide were significantly more frequent in patients with DC than relatives (42% versus 12%; p=0.008). The cumulative incidence of pulmonary disease by age 20 years was 55% in patients with DC with baseline PFT abnormalities compared with 17% in those with normal PFTs (p=0.02). None of the relatives developed pulmonary disease. X-linked recessive, autosomal recessive inheritance or heterozygous TINF2 variants were associated with early-onset pulmonary disease that mainly developed after haematopoietic cell transplantation (HCT). Overall, seven of 14 patients developed pulmonary disease post-HCT at a median of 4.7 years (range 0.7–12). The cumulative incidence of pulmonary fibrosis in patients with heterozygous non-TINF2 pathogenic variants was 70% by age 60 years.

Baseline PFT abnormalities are common in patients with DC and associated with progression to significant pulmonary disease. Prospective studies are warranted to facilitate clinical trial development for patients with DC and related TBDs.

About 40% of patients with dyskeratosis congenita, a telomere biology disorder, have abnormal pulmonary function tests and progress to life-threatening pulmonary disease (PD). Prospective therapeutic studies of PD in these disorders are urgently needed.http://bit.ly/2HBSNCO

An update on the biology and management of dyskeratosis congenita and related telomere biology disorders

Introduction: Telomere biology disorders (TBDs) encompass a group of illnesses caused by germline mutations in genes regulating telomere maintenance, resulting in very short telomeres. Possible TBD manifestations range from complex multisystem disorders with onset in childhood such as dyskeratosis congenita (DC), Hoyeraal-Hreidarsson syndrome, Revesz syndrome and Coats plus to adults presenting with one or two DC-related features.Areas covered: The discovery of multiple genetic causes and inheritance patterns has led to the recognition of a spectrum of clinical features affecting multiple organ systems. Patients with DC and associated TBDs are at high risk of bone marrow failure, cancer, liver and pulmonary disease. Recently, vascular diseases, including pulmonary arteriovenous malformations and gastrointestinal telangiectasias, have been recognized as additional manifestations. Diagnostics include detection of very short leukocyte telomeres and germline genetic testing. Hematopoietic cell transplantation and lung transplantation are the only current therapeutic modalities but are complicated by numerous comorbidities. This review summarizes the pathophysiology underlying TBDs, associated clinical features, management recommendations and therapeutic options.Expert opinion: Understanding TBDs as complex, multisystem disorders with a heterogenous genetic background and diverse phenotypes, highlights the importance of clinical surveillance and the urgent need to develop new therapeutic strategies to improve health outcomes.

Telomeropathies: Etiology, diagnosis, treatment and follow-up. Ethical and legal considerations

Telomeropathies involve a wide variety of infrequent genetic diseases caused by mutations in the telomerase maintenance mechanism or the DNA damage response (DDR) system. They are considered a family of rare diseases that often share causes, molecular mechanisms and symptoms. Generally, these diseases are not diagnosed until the symptoms are advanced, diminishing the survival time of patients. Although several related syndromes may still be unrecognized this work describes those that are known, highlighting that because they are rare diseases, physicians should be trained in their early diagnosis. The etiology and diagnosis are discussed for each telomeropathy and the treatments when available, along with a new classification of this group of diseases. Ethical and legal issues related to this group of diseases are also considered.

The histopathology of bone marrow failure in children

Bone marrow failure (BMF) is a rare but life-threatening disorder that usually manifests as (pan)cytopenia. BMF can be caused by a variety of diseases, but inherited BMF (IBMF) syndromes are a clinically important cause, especially in children. IBMF syndromes are a heterogeneous group of genetic disorders characterized by BMF, physical abnormalities, and predisposition to malignancy. An accurate diagnosis is critical, as disease-specific management, surveillance, and genetic counselling are required for each patient. The major differential diagnoses of IBMF syndromes are acquired aplastic anemia (AA) and refractory cytopenia of childhood (RCC). These diseases have overlapping features, such as BM hypocellularity and/or dysplastic changes, which make the differential diagnosis challenging. RCC has been defined as a histomorphologically distinct entity. Therefore, understanding the BM histopathology of these diseases is essential for the differential diagnosis. However, the BM histopathological features have not been characterized in detail, as descriptions of BM histopathology are very limited due to the rarity of the diseases. This review provides a detailed description of the BM histopathology in cases of RCC, AA, and the four most common IBMF syndromes: Fanconi anemia (FA), dysketatosis congenita (DC), Diamond-Blackfan anemia (DBA), and Shwachman-Diamond syndrome (SDS). An overview, including the clinical features and diagnosis, is also provided.

Telomeropathies: rare disease syndromes

Telomeres are located at the end of the chromosomes. They protect chromosomes from fusion and degradation. Every cell division causes a shortening of the telomeres. A special enzymatic complex called telomerase is responsible for maintaining telomere length in intensively dividing cells, such as epithelial cells and bone marrow cells. The enzymatic complex includes the TERT subunit, which has reverse transcriptase activity, and the TERC subunit, which acts as a template. Other important components of telomerase are the proteins that are responsible for structural stability. Telomerase remains active only in the dividing cells of the body. The rate of telomere shortening depends on many factors including age, sex, and comorbidities. Faster shortening of telomeres is caused by gene defects, which have an impact on telomerase action. Collectively, these are called telomeropathies. Common causes of telomeropathies are mutations in the TERT and TERC telomerase genes. Types of telemeropathies include dyskeratosis congenita, idiopathic pulmonary fibrosis, and aplastic anaemia, among others. Clinical manifestations and prognoses depend on the type and quantity of mutated genes. Diagnosis of telomeropathies is often problematic because they present with the same symptoms as other diseases. So far, no effective therapeutic methods have been developed for telomeropathies. A therapeutic method for patients with bone marrow failure may be the transplantation of hematopoietic stem cells. For patients with idiopathic pulmonary fibrosis, treatments include immunosuppressive therapy, lung transplantation, or palliative care. In the future, gene therapy may be an effective treatment strategy for telomeropathies. Lifestyle changes may also have a positive impact on the person. Physical activity combined with a healthy diet rich in antioxidants and unsaturated fatty acids can decrease the oxidative stress levels in cells and lead to a slower shortening of the telomeres.

Dyskeratosis congenita with a novel genetic variant in the DKC1 gene: a case report

Background

Dyskeratosis congenita (DC) is a rare genetic disorder of bone marrow failure inherited in an X-linked, autosomal dominant or autosomal recessive pattern. It has a wide array of clinical features and patients may be cared for by many medical sub specialties. The typical clinical features consist of lacy reticular skin pigmentation, nail dystrophy and oral leukoplakia. As the disease advances, patients may develop progressive bone marrow failure, pulmonary fibrosis, oesophageal stenosis, urethral stenosis, liver cirrhosis as well as haematological and solid malignancies. Several genes have been implicated in the pathogenesis of dyskeratosis congenita, with the dyskerin pseudouridine synthase 1 (DKC1) gene mutations being the X-linked recessive gene.

Case presentation

Herein, we report a 31-year-old male with history of recurrent febrile episodes who was found to have reticulate skin pigmentation interspersed with hypopigmented macules involving the face, neck and extremities, hyperkeratosis of palms and soles, nail dystrophy, leukoplakia of the tongue, premature graying of hair, watery eyes and dental caries. Several of his male relatives, including two maternal uncles and three maternal cousins were affected with a similar type of disease condition. Pedigree analysis suggested a possible X-linked pattern of inheritance. Genetic testing in the proband showed a novel hemizygous, non-synonymous likely pathogenic variant [NM_001363.4: c.1054A > G: p.Thr352Ala] in the PUA domain of the DKC1 gene. Quantitative polymerase chain reaction for relative telomere length measurements performed in the proband showed that he had very short telomeres [0.38, compared to a control median of 0.71 (range 0.44–1.19)], which is consistent with the DC diagnosis. Co-segregation analysis of the novel mutation and telomere length measurements in the extended family members could not be performed as they were unwilling to provide consent for testing.

Conclusions

The novel variant detected in the DKC1 gene adds further to the existing scientific literature on the genotype-phenotype correlation of DC, and has important implications for the clinical and molecular characterization of the disease.

Beginning at the ends: telomeres and human disease

Studies of rare and common illnesses have led to remarkable progress in the understanding of the role of telomeres (nucleoprotein complexes at chromosome ends essential for chromosomal integrity) in human disease. Telomere biology disorders encompass a growing spectrum of conditions caused by rare pathogenic germline variants in genes encoding essential aspects of telomere function. Dyskeratosis congenita, a disorder at the severe end of this spectrum, typically presents in childhood with the classic triad of abnormal skin pigmentation, nail dystrophy, and oral leukoplakia, accompanied by a very high risk of bone marrow failure, cancer, pulmonary fibrosis, and other medical problems. In contrast, the less severe end of the telomere biology disorder spectrum consists of middle-age or older adults with just one feature typically seen in dyskeratosis congenita, such as pulmonary fibrosis or bone marrow failure. In the common disease realm, large-scale molecular epidemiology studies have discovered novel associations between illnesses, such as cancer, heart disease, and mental health, and both telomere length and common genetic variants in telomere biology genes. This review highlights recent findings of telomere biology in human disease from both the rare and common disease perspectives. Multi-disciplinary collaborations between clinicians, basic scientists, and epidemiologist are essential as we seek to incorporate new telomere biology discoveries to improve health outcomes.

Revesz syndrome masquerading as traumatic retinal detachment

A 13-month-old boy with mild hemophilia A presented for strabismus evaluation and was found to have retinal hemorrhages in the right eye, left exotropia, and left total retinal detachment. These findings were attributed to trauma and hemophilia A. Routine blood work for hemophilia A subsequently showed pancytopenia. A bone marrow aspirate showed marked hypocellularity consistent with severe aplastic anemia, and telomere testing revealed very short telomeres. The patient was found to have a TINF2 mutation consistent with a diagnosis of Revesz syndrome, a variant of dyskeratosis congenita. He underwent successful bone marrow transplantation, and on subsequent evaluation was found to have retinal hemorrhages, vessel sclerosis, and cotton wool spots in the right eye associated with peripheral retinal nonperfusion. He underwent retinal laser treatment to the areas of retinal nonperfusion which resulted in stable visual function.

PERIPHERAL RETINOPATHY ASSOCIATED WITH APLASTIC ANEMIA

PURPOSE

To report a case of severe, bilateral, rapidly progressing peripheral retinal nonperfusion associated with underlying aplastic anemia.

METHODS

An interventional case report.

RESULTS

A 4-year-old girl presented with decreased visual acuity. On clinical examination, she was found to have a RAPD, elevated intraocular pressure, 360° rubeosis, vitreous hemorrhage, severe exudative retinal detachment, and telangiectasia with severe peripheral retinal nonperfusion. Laboratory workup was significant for pancytopenia, and a bone marrow biopsy showed extreme hypocellularity with no malignant cells. The patient was diagnosed with primary aplastic anemia. She developed dramatic progression of retinal nonperfusion in the left eye, as well as in the fellow right eye. This bilateral retinopathy was poorly responsive to aggressive management, which included laser photocoagulation and intravitreal injections of anti-vascular endothelial growth factor medications.

CONCLUSION

Asymmetric, bilateral quickly progressing peripheral retinal ischemia, in conjunction with pancytopenia and otherwise negative workup may be related to underlying bone marrow failure and aplastic anemia.

RETINAL VASCULAR TORTUOSITY AND EXUDATIVE RETINOPATHY IN A FAMILY WITH DYSKERATOSIS CONGENITA MASQUERADING AS FAMILIAL EXUDATIVE VITREORETINOPATHY

PURPOSE

To report a novel presentation of dyskeratosis congenita masquerading as familial exudative vitreoretinopathy.

METHODS

Observational case series involving single family and literature review.

RESULTS

A brother and sister were diagnosed with familial exudative vitreoretinopathy at ages 4 and 2, respectively. Both patients were managed with laser photocoagulation. Eight years after the initial presentation, both siblings developed pancytopenia secondary to bone marrow failure. Laboratory work-up revealed severely shortened telomere length in both patients, and genetic testing revealed a missense mutation in the gene that encodes the reverse transcriptase component of telomerase, confirming the diagnosis of dyskeratosis congenita. The father of both children was a carrier of the same mutation, who exhibited marked retinal vascular tortuosity of the second-order vessels.

CONCLUSION

Dyskeratosis congenita is a severe multisystem disorder, which should be considered in cases of pediatric exudative retinopathies with concurrent signs and/or symptoms of bone marrow failure.

The genomics of inherited bone marrow failure: from mechanism to the clinic

The inherited bone marrow failure syndromes (IBMFS) typically present with significant cytopenias in at least one haematopoietic cell lineage that may progress to pancytopenia, and are associated with increased risk of cancer. Although the clinical features of the IBMFS are often diagnostic, variable disease penetrance and expressivity may result in diagnostic dilemmas. The discovery of the genetic aetiology of the IBMFS has been greatly facilitated by next-generation sequencing methods. This has advanced understanding of the underlying biology of the IBMFS and been essential in improving clinical management and genetic counselling for affected patients. Herein we review the clinical features, underlying biology, and new genomic discoveries in the IBMFS, including Fanconi anaemia, dyskeratosis congenita, Diamond Blackfan anaemia, Shwachman Diamond syndrome and some disorders of the myeloid and megakaryocytic lineages.

The wide-ranging clinical implications of the short telomere syndromes

There is an increasing number of inherited disorders in which excessive telomere shortening underlies the molecular defect, with dyskeratosis congenita (DC) being the archetypal short telomere syndrome. DC is classically described as a mucocutaneous triad of oral leukoplakia, nail dystrophy and abnormal skin pigmentation. However, excessive telomere shortening can affect almost any organ system, so the clinical manifestations are protean, including developmental delay, cerebellar hypoplasia, exudative retinopathy, aplastic anaemia, acute myeloid leukaemia, idiopathic pulmonary fibrosis, idiopathic hepatic cirrhosis, head and neck cancer and dental abnormalities, and may be multi-systemic. Undiagnosed patients may be seen by essentially any medical subspecialist. Correct diagnosis is important to ensure appropriate management, and for initiating investigations to identify affected family members. Treatment is often supportive, with transplantation offering cure for pulmonary fibrosis or bone marrow failure. Higher rates of mortality and morbidity with transplantation often require regimen alterations, underscoring the need for correct diagnosis. Short telomeres result from mutations in genes essential for telomere maintenance (e.g. genes encoding subunits of the telomerase enzyme complex). Disease severity reflects not only the severity of the defect, but also the inheritance of short telomeres, giving rise to incomplete penetrance and genetic anticipation. Attendees of the inaugural Australian Short Telomere Syndrome Conference were updated on the current scientific and clinical understanding of these disorders, and discussed the best approach for management of these patients in the Australian context. This review will include recommendations from the conference and aims to increase awareness of short telomere disorders.

Bilateral Proliferative Retinopathy Associated With Hoyeraal-Hreidarsson Syndrome, a Severe Form of Dyskeratosis Congenita

Dyskeratosis congenita (DC) is the prototypical member of a family of diseases caused by defective telomere maintenance. These "telomeropathies" also include Hoyeraal-Hreidarsson syndrome (HH) and Revesz syndrome, which are severe forms of dyskeratosis congenita, as well as a subset of idiopathic pulmonary fibrosis, aplastic anemia, and Coats' plus syndrome. Retinopathy has only rarely been reported in DC and HH, but is universally present in Coats' plus and Revesz syndromes. The care of these patients is typically a multidisciplinary effort, and this should include monitoring by an ophthalmologist.

The molecular genetics of the telomere biology disorders

The importance of telomere function for human health is exemplified by a collection of Mendelian disorders referred to as the telomere biology disorders (TBDs), telomeropathies, or syndromes of telomere shortening. Collectively, the TBDs cover a spectrum of conditions from multisystem disease presenting in infancy to isolated disease presentations in adulthood, most notably idiopathic pulmonary fibrosis. Eleven genes have been found mutated in the TBDs to date, each of which is linked to some aspect of telomere maintenance. This review summarizes the molecular defects that result from mutations in these genes, highlighting recent advances, including the addition of PARN to the TBD gene family and the discovery of heterozygous mutations in RTEL1 as a cause of familial pulmonary fibrosis.

Unraveling the pathogenesis of Hoyeraal-Hreidarsson syndrome, a complex telomere biology disorder

Hoyeraal-Hreidarsson (HH) syndrome is a multisystem genetic disorder characterized by very short telomeres and considered a clinically severe variant of dyskeratosis congenita. The main cause of mortality, usually in early childhood, is bone marrow failure. Mutations in several telomere biology genes have been reported to cause HH in about 60% of the HH patients, but the genetic defects in the rest of the patients are still unknown. Understanding the aetiology of HH and its diverse manifestations is challenging because of the complexity of telomere biology and the multiple telomeric and non-telomeric functions played by telomere-associated proteins in processes such as telomere replication, telomere protection, DNA damage response and ribosome and spliceosome assembly. Here we review the known clinical complications, molecular defects and germline mutations associated with HH, and elucidate possible mechanistic explanations and remaining questions in our understanding of the disease.

X-linked dyskeratosis congenita presenting in adulthood with photodamaged skin and epiphora

Dyskeratosis congenita (DC) is a clinically and genetically heterogeneous multisystem bone marrow failure disorder of telomere maintenance, which may present with dermatological features. The main cause of mortality is bone marrow failure, often developing in the second decade of life, although pulmonary disease and malignancies such as squamous cell carcinomas (SCCs) may also prove fatal. We report the case of a 28-year-old man with X-linked DC and confirmed DKC1 gene mutation. In addition to the classic triad of nail dystrophy, hyperpigmentation and oral leucoplakia, the patient had actinic keratosis (AK) and photodamaged skin, hitherto under-recognized features of this condition. Awareness of the clinical presentation of DC is important, as accurate clinical and molecular diagnosis affords patients and their families genetic counselling, cancer prevention and screening measures, and planning for complications such as bone marrow failure.

Dyskeratosis congenita caused by a novel TERT point mutation in siblings with pancytopenia and exudative retinopathy

Two siblings presenting with exudative retinopathy, thrombocytopenia, and macrocytosis were found to have markedly shortened telomeres and a previously unreported inherited mutation in TERT, c.2603A>G. Revesz syndrome, a subtype of dyskeratosis congenita (DC) caused by TINF2 mutation, combines marrow failure with exudative retinopathy, intracranial calcifications, and neurocognitive impairment. As our patients manifested neither intracranial calcification nor significant neurocognitive impairment, we conclude that the c.2603A>G TERT mutation may define a subtype of DC manifesting first as exudative retinopathy without other signs of DC. Children with exudative retinopathy should be periodically screened for macrocytosis and cytopenias to evaluate for underlying DC.

Ocular manifestations of idiopathic aplastic anemia: retrospective study and literature review

Aplastic anemia (AA) is a rare disease with few reports on its ophthalmic manifestations. The ocular findings are described in a retrospective consecutive series of 719 AA Korean patients followed at the Hematology Clinic of The Catholic University of Korea. Out of a total of 719 patients, 269 patients had eye examinations, 156 patients had retinal evaluation, and 37 (23.7%) had retinal findings. These 37 patients had unilateral retinal hemorrhage in seven and bilateral retinal hemorrhage in 30 with mean hemoglobin of 6.6 g/dL (range 2.7–12.6 g/dL) and platelet counts of 18.8×10⁹/L (range 4–157×10⁹/L); central retinal vein occlusion-like picture occurred in nine patients and these had similar rheology to the rest of the subjects; optic disc edema, cotton-wool spots, macular edema, and dry eyes occurred in two, three, five, and three patients, respectively. In this Korean series of 141 subjects with AA, systemic bleeding occurred in 24.8% of subjects, retinal hemorrhage in 37% of subjects, and any bleeding site (eye or elsewhere) occurred in 47.5% of subjects with AA. A literature review (1958–2010) of 200 AA cases revealed retinal hemorrhages in 56%, subhyaloid or vitreous hemorrhage in 9%, peripheral retinal vasculopathy in 5.5%, and cotton-wool spots, Sjögren’s syndrome, or optic disc edema in 4% each. The prevalence of retinopathy among series of AA patients varied from 20% to 28.3%, which is consistent with the Korean series of 24.8%. Management of AA patients needs to involve multiple specialties, including hematologists, ophthalmologists, and infectious disease specialists.

Human telomeres and telomere biology disorders

Telomeres consist of long nucleotide repeats and a protein complex at chromosome ends essential for chromosome stability. Telomeres shorten with each cell division and thus are markers of cellular age. Dyskeratosis congenita (DC) is a cancer-prone inherited bone marrow failure syndrome caused by germ-line mutations in key telomere biology genes that result in extremely short telomeres. The triad of nail dysplasia, abnormal skin pigmentation, and oral leukoplakia is diagnostic of DC but highly variable. Patients with DC may also have but numerous other medical problems, including pulmonary fibrosis, liver abnormalities, avascular necrosis of the hips, and stenosis of the esophagus, lacrimal ducts, and/or urethra. All modes of inheritance have been reported in DC and de novo mutations are common. Broad phenotypic heterogeneity occurs within DC. Clinically severe variants of DC are Hoyeraal-Hreidarsson syndrome and Revesz syndrome. Coats plus syndrome joined the spectrum of DC with the discovery that it is caused by mutations in a telomere-capping gene. Less clinically severe variants, such as subsets of apparently isolated aplastic anemia or pulmonary fibrosis, have also been recognized. These patients may not have the DC-associated mucocutaneous triad or complicated medical features, but they do have the same underlying genetic etiology. This has led to the use of the descriptive term telomere biology disorder (TBD). This chapter will review the connection between telomere biology and human disease through the examples of DC and its related TBDs.

Updates on the biology and management of dyskeratosis congenita and related telomere biology disorders

Dyskeratosis congenita (DC) is a cancer-prone inherited bone marrow failure syndrome caused by aberrant telomere biology. The mucocutaneous triad of nail dysplasia, abnormal skin pigmentation and oral leukoplakia is diagnostic, but is not always present; DC can also be diagnosed by the presence of very short leukocyte telomeres. Patients with DC are at high risk of bone marrow failure, pulmonary fibrosis, liver disease, cancer and other medical problems. Germline mutations in one of nine genes associated with telomere maintenance are present in approximately 60% of patients. DC is one among the group of clinically and biologically related telomere biology disorders, including Hoyeraal-Hreidarsson syndrome, Revesz syndrome, Coats plus (also known as cranioretinal microangiopathy with calcifications and cysts) and subsets of aplastic anemia, pulmonary fibrosis, nonalcoholic and noninfectious liver disease and leukemia. The authors review the pathobiology that connects DC and the related telomere biology disorders, methods of diagnosis and management modalities.

Short telomeres: from dyskeratosis congenita to sporadic aplastic anemia and malignancy

Telomeres are DNA-protein structures that form a protective cap on chromosome ends. As such, they prevent the natural ends of linear chromosomes from being subjected to DNA repair activities that would result in telomere fusion, degradation, or recombination. Both the DNA and protein components of the telomere are required for this essential function, because insufficient telomeric DNA length, loss of the terminal telomeric DNA structure, or deficiency of key telomere-associated factors may elicit a DNA damage response and result in cellular senescence or apoptosis. In the setting of failed checkpoint mechanisms, such DNA-protein defects can also lead to genomic instability through telomere fusions or recombination. Thus, as shown in both model systems and in humans, defects in telomere biology are implicated in cellular and organismal aging as well as in tumorigenesis. Bone marrow failure and malignancy are 2 life-threatening disease manifestations in the inherited telomere biology disorder dyskeratosis congenita. We provide an overview of basic telomere structure and maintenance. We outline the telomere biology defects observed in dyskeratosis congenita, focusing on recent discoveries in this field. Last, we review the evidence of how telomere biology may impact sporadic aplastic anemia and the risk for various cancers.

Revesz syndrome masquerading as bilateral cicatricial retinopathy of prematurity

Dyskeratosis congenita is a group of rare genetic bone marrow failure syndromes. Revesz syndrome, a variant disorder, is characterized by retinopathy, aplastic anemia, nail dystrophy, and cerebellar hypoplasia. We report the case of an 11-month-old boy with bilateral cicatricial retinal detachments associated with fibrovascular proliferation. Genetic testing ultimately confirmed a diagnosis of Revesz syndrome, which can mimic cicatricial retinopathy of prematurity. Prompt referral to a hematologist expedites diagnosis and treatment.

Dyskeratosis congenita- management and review of complications: a case report

Among the inherited bone marrow failure disorders, dyskeratosis congenita is an X-linked inherited disorder arising as a consequence of short telomere and mutations in telomere biology. Production of the altered protein dyskerin, leads to vulnerable skin, nails, and teeth which lead to higher permeability for noxious agents which can induce carcinogenesis accounting for the classical triad of skin pigmentation, nail dystrophy and oral leukoplakia. This condition is fatal and patients succumb to aplastic anemia, malignancy or immunocompromised state. We present a young male with the classic clinical triad and avascular necrosis of both femoral heads, with no evidence of hematologic anomaly or any malignancy. He was managed for osteonecrosis with uncemented total hip arthroplasty for the symptomatic left hip. Our case represents a benign form of such a fatal and rare condition, which if detected and managed early can result in improved quality of life for the patient suffering from this disorder. This patient is under our meticulous follow-up for the last 2 years in order to determine any late development of complications before being labelled as a variant of this syndrome.

Posttransplant Lymphoproliferative Disorder Complicating Hematopoietic Stem Cell Transplantation in a Patient With Dyskeratosis Congenita

Dyskeratosis congenita (DC) is a rare inherited disorder characterized by bone marrow failure and cancer predisposition. We present a case of a 28-year-old woman with DC who was admitted for hematopoietic stem cell transplantation (HSCT) for aplastic anemia and who developed acute myeloid leukemia with complex genetic karyotype abnormalities including the MLL (11q23) gene, 1q25, and chromosome 8. After transplantation, a monomorphic Epstein–Barr virus (EBV) negative posttransplant-associated lymphoproliferative disorder (PTLD) diffuse large B-cell lymphoma was discovered involving the liver, omental tissue, and peritoneal fluid samples showing additional MLL (11q23) gene abnormalities by fluorescence in situ hybridization. Despite treatment, the patient died of complications associated with transplantation and invasive fungal infection. This case represents the first bona fide documented case of EBV-negative monomorphic PTLD host derived, with MLL gene abnormalities in a patient with DC, and shows another possible mechanism for the development of a therapy-related lymphoid neoplasm after transplantation.