Brain imaging features of children with Hoyeraal-Hreidarsson syndrome

Brain Calcifications: Genetic, Molecular, and Clinical Aspects

Many conditions can present with accumulation of calcium in the brain and manifest with a variety of neurological symptoms. Brain calcifications can be primary (idiopathic or genetic) or secondary to various pathological conditions (e.g., calcium-phosphate metabolism derangement, autoimmune disorders and infections, among others). A set of causative genes associated with primary familial brain calcification (PFBC) has now been identified, and include genes such as SLC20A2, PDGFB, PDGFRB, XPR1, MYORG, and JAM2. However, many more genes are known to be linked with complex syndromes characterized by brain calcifications and additional neurologic and systemic manifestations. Of note, many of these genes encode for proteins involved in cerebrovascular and blood-brain barrier functions, which both represent key anatomical structures related to these pathological phenomena. As a growing number of genes associated with brain calcifications is identified, pathways involved in these conditions are beginning to be understood. Our comprehensive review of the genetic, molecular, and clinical aspects of brain calcifications offers a framework for clinicians and researchers in the field.

The role of post-transcriptional modifications during development

While the existence of post-transcriptional modifications of RNA nucleotides has been known for decades, in most RNA species the exact positions of these modifications and their physiological function have been elusive until recently. Technological advances, such as high-throughput next-generation sequencing (NGS) methods and nanopore-based mapping technologies, have made it possible to map the position of these modifications with single nucleotide accuracy, and genetic screens have uncovered the “writer”, “reader” and “eraser” proteins that help to install, interpret and remove such modifications, respectively. These discoveries led to intensive research programmes with the aim of uncovering the roles of these modifications during diverse biological processes. In this review, we assess novel discoveries related to the role of post-transcriptional modifications during animal development, highlighting how these discoveries can affect multiple aspects of development from fertilization to differentiation in many species.

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.

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.

Brain imaging features of children with Hoyeraal-Hreidarsson syndrome

OBJECTIVE

This study aimed to summarize the magnetic resonance imaging (MRI) and computed tomography (CT) features of the central nervous system (CNS) in children with Hoyeraal-Hreidarsson syndrome.

METHODS

The imaging and clinical data of four children diagnosed with Hoyeraal-Hreidarsson syndrome by clinical and laboratory tests in the Guangzhou Women and Children's Medical Center were gathered and analyzed retrospectively. The clinical manifestations and CNS imaging features of Hoyeraal-Hreidarsson syndrome were summarized based on our results and a literature review.

RESULTS

Our results showed that delayed development, skin pigmentation, nail/toenail dystrophy, thrombocytopenia, and anemia are the most observed clinical presentations of Hoyeraal-Hreidarsson syndrome. Important findings on CNS imaging showed that all patients had cerebellar hypoplasia, delayed myelination, hydrocephalus, brain atrophy, and calcification. The gene mutations in all cases were consistent with those of dyskeratosis congenita, including TINF2 mutations in three cases and DKC1 mutations in one case.

CONCLUSION

Hoyeraal-Hreidarsson syndrome is a severe variant of dyskeratosis congenita. Both DKC1 and TINF2 mutations can lead to the phenotypes of Hoyeraal-Hreidarsson syndrome. In our study, CNS imaging revealed that cerebellar hypoplasia has an important diagnostic value for Hoyeraal-Hreidarsson syndrome while delayed myelination, calcification of the parenchyma, brain atrophy, and hydrocephalus are also important findings on CNS imaging. Combining imaging features with clinical and laboratory indicators can assist the diagnosis of Hoyeraal-Hreidarsson syndrome.