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Items: 11

1.

Schizophrenia

Schizophrenia is highly heritable, as shown by family, twin, and adoption studies. For example, for identical twins, if one twin develops schizophrenia, the other twin has about a 50% chance of also developing the disease. The risk of the general population developing the schizophrenia is about 0.3-0.7% worldwide. The search for “schizophrenia genes” has been elusive. Initial linkage studies looked at parts of the genome associated with schizophrenia, and many candidate genes were identified, including APOE, COMT, DAO, DRD1, DRD2, DRD4, DTNBP1, GABRB2, GRIN2B, HP, IL1B, MTHFR, PLXNA2, SLC6A4, TP53, and TPH1. However, some of these have later been questioned. Microdeletions and microduplications have been found to be three times more common in individuals with schizophrenia, compared to controls. Because these deletions and duplications are in genes that are overexpressed in pathways related to brain development, it is possible that the inheritance of multiple rare variants may contribute to the development of schizophrenia. Several genetic disorders feature schizophrenia as a clinical feature. The 22q11.2 Deletion Syndrome comprises many different syndromes, of which one of the most serious is DiGeorge syndrome. Children born with DiGeorge syndrome typically have heart defects, cleft palate, learning difficulties, and immune deficiency. Schizophrenia is a late manifestation, affecting around 30% of individuals. Microdeletions and duplications in chromosome 1, 2, 3, 7, 15 and 16 have also been associated with schizophrenia. In 2014, a genome-wide association study looked at the genomes of over 35,000 patients and 110,00 controls. The study identified 108 SNPs that were associated with schizophrenia, 83 of which had not been previously reported. As expected, many of these loci occurred in genes that are expressed in the brain. For example, the SNPs included a gene that encodes the dopamine D2 receptor, DRD2 (the target of antipsychotic drugs), and many genes involved in glutamine neurotransmitter pathways and synaptic plasticity (e.g., GRM3, GRIN2A, SRR, GRIA1). More surprisingly, however, associations were also enriched among genes expressed in tissues with important immune functions. In 2016, a study based on nearly 65,000 people investigated the association between schizophrenia and variation in the Major Histocompatibility Complex (MHC) locus—a region on chromosome 6 that is important for immune function. The study focused on the C4 gene (complement component 4) that exists as two distinct genes: C4A and C4B, which encode particularly structurally diverse alleles. The study found that the alleles which promoted greater expression of C4A in the brain were associated with a greater risk of schizophrenia. By using mice models, the study showed that C4 is involved in the elimination of synapses during brain maturation. In humans, “synaptic pruning” is most active during late adolescence, which coincides with the typical onset of symptoms of schizophrenia. It is therefore possible that the inheritance of specific C4A alleles could lead to “run away” synaptic pruning, increasing the risk of schizophrenia. Further research may even determine C4 as a potential therapeutic target. [from GTR]

MedGen UID:
48574
Concept ID:
C0036341
Mental or Behavioral Dysfunction
2.

Schizophrenia

A mental disorder characterized by a disintegration of thought processes and of emotional responsiveness. It most commonly manifests as auditory hallucinations, paranoid or bizarre delusions, or disorganized speech and thinking, and it is accompanied by significant social or occupational dysfunction. The onset of symptoms typically occurs in young adulthood, with a global lifetime prevalence of about 0.3-0.7%. [from HPO]

MedGen UID:
506532
Concept ID:
CN117643
Finding
3.

Enthesitis-related arthritis

MedGen UID:
798421
Concept ID:
CN206193
Finding
4.

Regression

Return to a former state; a subsidence of the symptoms of a disease process; in cancer, a decrease in the size of a tumor or in the extent of cancer in the body. [from NCI]

MedGen UID:
195771
Concept ID:
C0684320
Pathologic Function
5.

Heterogeneous

The presence of apparently similar characters for which the genetic evidence indicates that different genes or different genetic mechanisms are involved in different pedigrees. In clinical settings genetic heterogeneity refers to the presence of a variety of genetic defects which cause the same disease, often due to mutations at different loci on the same gene, a finding common to many human diseases including ALZHEIMER DISEASE; CYSTIC FIBROSIS; LIPOPROTEIN LIPASE DEFICIENCY, FAMILIAL; and POLYCYSTIC KIDNEY DISEASES. (Rieger, et al., Glossary of Genetics: Classical and Molecular, 5th ed; Segen, Dictionary of Modern Medicine, 1992) [from MeSH]

MedGen UID:
67020
Concept ID:
C0242960
Organism Attribute
6.

Disease Attributes

Clinical characteristics of disease or illness. [from MeSH]

MedGen UID:
199876
Concept ID:
C0752357
Disease or Syndrome
7.

Schizophrenia Spectrum and Other Psychotic Disorders

Marked disorders of thought (delusions, hallucinations, or other thought disorder accompanied by disordered affect or behavior), and deterioration from a previous level of functioning. Individuals have one o more of the following symptoms: delusions, hallucinations, and disorganized speech. (from DSM-5) [from MeSH]

MedGen UID:
141907
Concept ID:
C0525046
Mental or Behavioral Dysfunction
8.

Diagnosis, Psychiatric

MedGen UID:
138165
Concept ID:
C0376338
Mental or Behavioral Dysfunction
9.

Genetic predisposition

A latent susceptibility to disease at the genetic level, which may be activated under certain conditions. [from MeSH]

MedGen UID:
137259
Concept ID:
C0314657
Organism Attribute
10.

Mental disorder

A disorder characterized by behavioral and/or psychological abnormalities, often accompanied by physical symptoms. The symptoms may cause clinically significant distress or impairment in social and occupational areas of functioning. Representative examples include anxiety disorders, cognitive disorders, mood disorders and schizophrenia. [from NCI]

MedGen UID:
14047
Concept ID:
C0004936
Mental or Behavioral Dysfunction
11.

Genetic Linkage

The co-inheritance of two or more non-allelic GENES due to their being located more or less closely on the same CHROMOSOME. [from MeSH]

MedGen UID:
6102
Concept ID:
C0023745
Molecular Function
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