Updates on the genetics of multiple endocrine neoplasia

Multiple endocrine neoplasia (MEN) is a group of syndromes with a genetic predisposition to the appearance of endocrine tumors, and shows autosomal dominant transmission. The advent of molecular genetics has led to improvements in the management of MEN in terms of diagnosis, prognosis and therapy. The genetics of MEN is the subject of regular updates, which will be presented throughout this paper. MEN1, the first to be described, is associated with the MEN1 gene. MEN1 is well known in terms of the observed phenotype, with genetic analysis being conclusive in 90% of patients with a typical phenotype, but is negative in around 10% of families with MEN1. Improvement in analysis techniques and the identification of other genes responsable for phenocopies allows the resolution of some, but not all, cases, notably non-familial forms suspected to be fortuitous assocations with tumors. MEN4 is a rare phenocopy of MEN1 linked to constitutional mutations in the CDKN1B gene. Though it closely resembles the phenotype of MEN1, published data suggests the appearance of tumors is later and less frequent in MEN4. MEN2, which results from mutations in the RET oncogene, shows a strong genotype-phenotype correlation. This correlation is particularly evident in the major manifestation of MEN2, medullary thyroid carcinoma (MTC), in which disease aggressiveness is dependent on the pathogenic variant of RET. However, recent studies cast doubt on this correlation between MTC and pathogenic variant. Lastly, the recent description of families carrying a mutation in MAX, which is known to predispose to the development of pheochromocytoma and paraganglioma, and presents a phenotypic spectrum that evokes MEN, suggests the existence of another syndrome, MEN5.

Late-Onset Psychosis and Phenocopies

Psychotic symptoms can manifest at any age, but in the elderly they represent a real diagnostic challenge. Thought disorders, hallucinations (usually visual), mood disorders with delusions, impairment of social interaction and occasionally verbal or physical aggression may be observed (Karon & VandenBos, 1998). Since the first descriptions of classical psychiatry, attempts have been made to define the psychoses observed in the elderly and determine whether they are primary "psychiatric" syndromes or, conversely, whether they can be attributed to other pathologies. Thus, different concepts have emerged, such as Late Onset Psychosis or Late-Onset Schizophrenia, Very Late-Onset Psychosis or Very Late-Onset Schizophrenia-Like Psychosis – VLOSL), Late-Life Psychosis, etc.

A narrative review on mild behavioural impairment: an exploration into its scientific perspectives

In clinical practice, the admission of patients with late-onset psychological and behavioural symptoms is frequent, regardless of the presence or absence of cognitive decline. These symptoms commonly occur in the prodromal stage of dementia and can precede the onset of dementia. While the concept of Mild Cognitive Impairment (MCI) -which is defined as a level of cognitive impairment insufficient to impact daily functioning- is well established, the notion of Mild Behavioural Impairment (MBI) is not yet widely recognized. However, studies have demonstrated that the presence of MBI in both cognitively normal patients and individuals with MCI is associated with an increased risk of dementia progression. Thus, MBI may serve as a neurobehavioral indicator of pre-dementia risk states. This narrative review aims to discuss the evolution of the term, the relevant clinical aspects, and potential biomarkers that may contribute to the clinical definition of MBI. The objective is to assist clinicians in recognizing the diagnosis and differentiating it from psychiatric syndromes, as well as identifying possible etiologies of neurodegeneration.

Cellular mechanisms and clinical applications for phenocopies of inborn errors of immunity: infectious susceptibility due to cytokine autoantibodies

INTRODUCTION

With a growing knowledge of Inborn error immunity (IEI), immunological profiling and genetic predisposition to IEI phenocopies have been developed in recent years.

AREAS COVERED

Here we summarized the correlation between various pathogen invasions, autoantibody profiles, and corresponding clinical features in the context of patients with IEI phenocopies. It has been extensively evident that patients with anti-cytokine autoantibodies underly impaired anti-pathogen immune responses and lead to broad unregulated inflammation and tissue damage. Several hypotheses of anti-cytokine autoantibodies production were summarized here, including a defective negative selection of autoreactive T cells, abnormal germinal center formation, molecular mimicry, HLA class II allele region, lack of auto-reactive lymphocyte apoptosis, and other possible hypotheses.

EXPERT OPINION

Phenocopies of IEI associated with anti-cytokine autoantibodies are increasingly recognized as one of the causes of acquired immunodeficiency and susceptibility to certain pathogen infections, especially facing the current challenge of the COVID-19 pandemic. By investigating clinical, genetic, and pathogenesis autoantibodies profiles associated with various pathogens' susceptibilities, we could better understand the IEI phenocopies with anti-cytokine autoantibodies, especially for those that underlie life-threatening SARS-CoV-2.

Beyond Sarcomeric Hypertrophic Cardiomyopathy: How to Diagnose and Manage Phenocopies

PURPOSE OF REVIEW

We describe the most common phenocopies of hypertrophic cardiomyopathy, their pathogenesis, and clinical presentation highlighting similarities and differences. We also suggest a step-by-step diagnostic work-up that can guide in differential diagnosis and management.

RECENT FINDINGS

In the last years, a wider application of genetic testing and the advances in cardiac imaging have significantly changed the diagnostic approach to HCM phenocopies. Different prognosis and management, with an increasing availability of disease-specific therapies, make differential diagnosis mandatory. The HCM phenotype can be the cardiac manifestation of different inherited and acquired disorders presenting different etiology, prognosis, and treatment. Differential diagnosis requires a cardiomyopathic mindset allowing to recognize red flags throughout the diagnostic work-up starting from clinical and family history and ending with advanced imaging and genetic testing. Different prognosis and management, with an increasing availability of disease-specific therapies make differential diagnosis mandatory.

The green-brown polymorphism of the club-legged grasshopper Gomphocerus sibiricus is heritable and appears genetically simple

Background

Local coexistence of distinct, genetically determined color morphs can be unstable and transitional. Stable, long-term coexistence requires some form of balancing selection to protect morphs from getting lost by directional selection or genetic drift. However, not all phenotypic polymorphism need to have a genetic basis. We here report on the genetic basis of two color polymorphisms in the club-legged grasshopper Gomphocerus sibiricus: a green-brown polymorphism that is phylogenetically and geographically widespread among orthopteran insects and a pied-brown pattern polymorphism that is shared among many gomphocerine grasshoppers.

Results

We found a remarkably clear outcome of matings within and between morph that suggest not only that the green-brown polymorphism is heritable in this species, but that results can be most parsimoniously explained by a single autosomal locus with two alleles in which the green allele is dominant over the brown allele. A few individuals did not match this pattern and suggest the existence of genetic modifiers and/or developmental phenocopies. We also show that the pied-brown polymorphism is highly heritable, although the evidence for the involvement of one or more loci is less clear-cut.

Conclusions

Overall, our data demonstrate that the two polymorphisms are heritable in the club-legged grasshopper and appear genetically simple, at least with respect to green morphs. The results are consistent with the idea that the synthesis or transport of a pigment involved in the production of green coloration (likely biliverdin) is lost by homozygosity for loss-of-function alleles in brown individuals. The apparently simple genetic architecture of the green-brown polymorphism offer potential for studying balancing selection in the field and for genetic mapping in this species.

Clinical spectrum, genetic complexity and therapeutic approaches for retinal disease caused by ABCA4 mutations

The ABCA4 protein (then called a “rim protein”) was first identified in 1978 in the rims and incisures of rod photoreceptors. The corresponding gene, ABCA4, was cloned in 1997, and variants were identified as the cause of autosomal recessive Stargardt disease (STGD1). Over the next two decades, variation in ABCA4 has been attributed to phenotypes other than the classically defined STGD1 or fundus flavimaculatus, ranging from early onset and fast progressing cone-rod dystrophy and retinitis pigmentosa-like phenotypes to very late onset cases of mostly mild disease sometimes resembling, and confused with, age-related macular degeneration. Similarly, analysis of the ABCA4 locus uncovered a trove of genetic information, including >1200 disease-causing mutations of varying severity, and of all types – missense, nonsense, small deletions/insertions, and splicing affecting variants, of which many are located deep-intronic. Altogether, this has greatly expanded our understanding of complexity not only of the diseases caused by ABCA4 mutations, but of all Mendelian diseases in general. This review provides an in depth assessment of the cumulative knowledge of ABCA4-associated retinopathy – clinical manifestations, genetic complexity, pathophysiology as well as current and proposed therapeutic approaches.

An updated review on phenocopies of primary immunodeficiency diseases

Primary immunodeficiency diseases (PIDs) refer to a heterogenous group of disorders characterized clinically by increased susceptibility to infections, autoimmunity and increased risk of malignancies.

These group of disorders present with clinical manifestations similar to PIDs with known genetic defects but have either no genetic defect or have a somatic mutation and thus have been labelled as “Phenocopies of PIDs”. These diseases have been further subdivided into those associated with somatic mutations and those associated with presence of auto-antibodies against various cytokines.

In this review, we provide an update on clinical manifestations, diagnosis and management of these diseases.

Syphilis

Syphilis is an infectious disease caused by a spirochete, Treponema pallidum; it is most commonly spread by sexual transmission. Syphilis is known as the "Great Imitator," as systemic manifestations are variable. It can involve any part of the eye, with syphilitic uveitis being the most common type. Congenital syphilis is characterized by Hutchinson's teeth, saddle nose deformity, deafness, and interstitial keratitis; pigmentary changes in the retina are varied and patchy.

Autoimmune Retinopathy

The autoimmune retinopathies (AIRs) are a group of inflammatory-mediated retinopathies that present with unexplained visual loss (both central and peripheral), visual field defects, usually a ring scotoma, photoreceptor dysfunction as evident on electroretinography (ERG), and circulating autoantibodies against retinal antigens. The fundus may be normal or may show vascular attenuation, retinal atrophy with or without pigmentary changes or waxy pallor of the optic disc, and no or minimal inflammatory cells.

Diffuse Unilateral Subacute Neuroretinitis (DUSN)

Diffuse unilateral subacute neuroretinitis (DUSN) is caused by a subretinal live and mobile nematode. Acute phase: Patients usually present with severe pain, decreased vision, vitritis/papillitis, and tracks of grayish-white lesions-and a live nematode. Late phase: Arterial narrowing, optic atrophy, diffuse disruption of the retinal pigment epithelium (RPE), with severe visual loss.

Rubella Retinopathy

DEFINITION

A phenocopy is an individual showing features (phenotype) characteristic of a genotype but produced environmentally rather than genetically (not inherited); these features are not due to mutations, as the underlying DNA sequence of the phenocopy is not altered.

Acute Zonal Occult Outer Retinopathy (AZOOR) and Related Diseases

Acute zonal occult outer retinopathy (AZOOR) is a presumed inflammatory disorder with outer retinal dysfunction. Typically, the onset is acute and it is unilateral, with symptoms of photopsias and nasal field loss; scotoma is usually contiguous with the optic nerve. Later, the other eye is involved in nearly three fourths of patients. The central vision remains good in most cases. Patients are usually young women with myopia. Fundus: May be normal in the beginning, but may show a grayish-white line at the border of normal and involved retina, usually in peripapillary area. This line disappears within weeks and is replaced with an orange zone. With time, retinal vessels attenuate and a large zone of retinal pigment epithelium (RPE) depigmentation appears, sort of a sector retinitis pigmentosa (RP) or unilateral or asymmetric RP. Rarely, mild vitritis may occur, and relative afferent pupillary defect (RAPD) is present in about 75% of cases.

Drug-Induced Retinal Toxicity

Drug-induced retinal toxicity can occur from the use of systemic, intravitreal, or topical medications. Despite the presence of the blood-ocular barrier, the retina is vulnerable to toxic effects of systemic medications leading to dysfunction and retinal degeneration. These toxicities can be categorized as damage to the retinal pigment epithelium (RPE) and photoreceptor complex, vascular damage, ganglion cell or optic nerve damage, cystoid macular edema, crystalline retinopathy, uveitis, changes in color vision and electroretinography (ERG), and other miscellaneous effects.

No evidence of increased breast cancer risk for proven noncarriers from BRCA1 and BRCA2 families

In families screened for mutations in the BRCA1 or BRCA2 genes and found to have a segregating mutation the breast cancer risk for women shown not to carry the family-specific mutation might be at above "average" risk. We assessed the risk of breast cancer in a clinic based cohort of 725 female proven noncarriers in 239 BRCA1 and BRCA2 families compared with birth-matched controls from the Danish Civil Registration System. Prospective analysis showed no significantly increased risk for breast cancer in noncarriers with a hazard ratio of 0.67 [95 % confidence interval (CI) 0.32-1.42, p = 0.29] for all family members who tested negative and 0.87 (95 % CI 0.38-1.97, p = 0.73) for non-carries who were first-degree relatives of mutation carriers. Proven noncarriers from BRCA1 and BRCA2 families have no markedly increased risk for breast cancer compared to the general population, and our data do not suggest targeted breast cancer surveillance for noncarriers from BRCA1 and BRCA2 families.