Essence of multifactorial pathology
In medical biology and genetics, it is important to clearly differentiate the causes of various pathologies. Unlike chromosomal abnormalities (such as trisomy of chromosome 21 or deletion of the short arm of chromosome 5), which cause severe syndromes on their own, multifactorial diseases have a different nature.
Their main feature is a hereditary predisposition. The presence of a genetic defect does not guarantee a 100% development of the disease. The disease manifests only when an unfavorable environmental impact is superimposed on the genetic background.
Genetic basis
The foundation of diseases with hereditary predisposition can be of two types:
- Polygenic basis. Many different genes contribute to the development of the pathology. These are classical multifactorial diseases, where the phenotype is determined by a combination of effects from several genes and the obligatory influence of environmental factors.
- Monogenic basis. The predisposition is associated with a mutation in a single gene. However, despite the presence of the defective gene, strictly defined provoking environmental factors are still required for phenotypic expression (the direct development of the disease itself).
Provoking environmental factors
Without an external trigger, a multifactorial disease may never manifest. The main groups of provoking factors include:
- Environmental pollution.
- Nutritional factors (dietary features).
- Pathological reactions to pharmacological drugs.
- Various physical and biological factors.
Classification and examples of diseases
Multifactorial diseases are generally divided into two major clinical groups:
1. Mental and nervous system diseases This group includes severe disorders of the central nervous system and psyche that require a specific external trigger against a background of predisposition. Examples:
- Schizophrenia
- Epilepsy
- Manic-depressive psychosis
- Multiple sclerosis
2. Mid-life somatic diseases These are the most common pathologies encountered by general practitioners and internists. They include:
- Coronary heart disease (CHD) and hypertension
- Peptic ulcer disease of the stomach and duodenum
- Bronchial asthma
- Diabetes mellitus
- Psoriasis
Briefly: answers to topical questions
What biological and physical environmental factors serve as specific triggers for the development of bronchial asthma?
Specific triggers of bronchial asthma include various infections, allergens, as well as climatic and exertional factors.
- Biological factors — house dust, mites, epidermal allergens (animal fur, dander, saliva), plant pollen, mold fungal spores, food allergens, and respiratory tract infections (predominantly viruses, including rhinoviruses and RSV in children).
- Physical factors — physical exertion (provoking exercise-induced asthma), inhalation of cold air, and meteorological factors (weather changes).
To remember the concept: "GENETICS loads the gun, but the ENVIRONMENT pulls the trigger." Without a combination of mutations and environmental factors, the disease will not develop.
Class and exam questions
Is Down syndrome (trisomy 21) a multifactorial disease?
No. Trisomy of chromosome 21, as well as deletion of the short arm of chromosome 5, belongs to chromosomal diseases. Multifactorial diseases require a combination of mutations and environmental factors.
Can a multifactorial disease have a monogenic nature?
Yes, the genetic basis can be monogenic. In this case, a mutation in a single gene is present, but provoking environmental factors are still needed for the disease to develop.
Which somatic diseases are classified as multifactorial?
Mid-life somatic diseases with a hereditary predisposition include hypertension, CHD, diabetes mellitus, bronchial asthma, psoriasis, and peptic ulcer disease.
What else to study on this topic
- Mechanisms of polygenic trait inheritance and their impact on the phenotype
- Pathological reactions to pharmacological drugs as a disease trigger
- The role of environmental pollution in the manifestation of genetic mutations
- The relationship between dietary factors and the development of mid-life somatic diseases
- Features of the phenotypic expression of monogenic mutations under environmental influence
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