Man has lived with diseases from time immemorial. In medical sciences, diseases are classified into many types. They can be communicable (those which can spread from one person to another), non-communicable (those which do not spread from one person to another), hereditary (those which run in families, spanning from parents through their offspring), and congenital (those which are present since birth).
Every human being carries 23 pairs of chromosomes. Chromosomes posses genes in them which determine how the individual will look, behave and sometimes what diseases he might be prone to. Some genes can undergo mutation (changes) and can give rise to diseases.
During the reproductive phases, the developing fetus receives one set of chromosomes from mother (23) and other set from father (23), forming 23 pairs again. In this process, sometimes, the chromosomes with mutated genes will get transferred to their children resulting in hereditary disease.
Further Classification of Hereditary Diseases
Hereditary diseases can be further classified into many types:
Monogenetic disorders: These are due to mutations in single gene. Monogenetic disorders can be related to autosomes (X chromosomes) or sex chromosomes (Y chromosomes). In addition to that, they can be dominant or recessive
Autosomal dominant means presence of that particular gene (even one single gene) that is inherited from either parent will definitely cause the disease. It means there is 50% of the chance that the child will inherit the disease.
Autosomal recessive means it need one pair of same mutated genes to be inherited from both the parents to cause the disease. Put simply, it means there is 25% probability that the child will inherit the disease.
Examples of Monogenetic Disorders and their occurrences
The most common monogenetic Autosomal dominantly inherited disorders include:
Familial Hypercholestremia (as seen in every 1 in 500 people)
Poly Cystic Kidney Disease (which occurs 1 in 1250 people)
Neurofibromatosis Type I (seen in every 1 in 2500 people)
Hereditary Spherocytosis (seen in every 1 in 5000 people)
Marfans Syndrome (seen in every 1 in 4000 people)
Huntington’s Disease (seen in every 1 in 15000 people).
The most common Monogenetic Autosomal recessively inherited disorders include:
Sickle Cell disease (seen in every 1 in 625 people)
Cystic Fibrosis (seen in every 1 in 2000 people)
Tachy Sach’s disease (seen in every 1 in 3000 people)
Phenyl Ketonuria (seen in every 1 in 12000 people)
Mucopolysaccharidosis (seen in every 1 in 25000 people)
Liposomal Acid Lipase Deficiency Disorder (seen in every 1 in 40,000 people)
Glycogen storage diseases (seen in every 1 in 50000 people)
Galactosemia (seen in every 1 in 57000 people).
In a similar vein, the most common X linked inherited disorders include:
Duchenne Muscular Dystrophy (seen in every 1 in 7000 people)
Hemophilia (seen in every 1 in 10,000 people).
Multifactorial disorders: These disorders have become common nowadays. They are present with all small inherited variations along with environmental effects that will add to it. Diabetes, Hypertension, Heart diseases are the most common multifactorial diseases.
Chromosomal disorders: Also, chromosomal disorders are usually due to deficiency or excess presence of chromosome. In this type of disorders, there is addition, deletion or formation of new chromosome, which results in specific disorders. Examples are:
Mitochondrial Inheritance Disorders: Unlike other disorders, Mitochondrial Inheritance Disorders rare. Mitochondria are cell organelles that are responsible for respiration and oxidation of food materials. Each mitochondrion has a nucleus that contains DNA. During reproduction, the fetus retains the mitochondria of the mother. Consequently, any change or mutation in mitochondrial DNA will lead to diseases like:
Down’s Syndrome: Extra copy of chromosome 21 is present. It is referred to as trisomy 21. Total chromosomes will be 47 with XXY
Prader Willi Syndrome: have you ever come across Prader Willi Syndrome? Well, this happens as a result of absence of Chromosome 15. Aside from the absence of Chromosome 15, non-expression can also lead to Prader Willi Syndrome
Chronic Myeloid Leukemia: This is a form of blood cancer where there is exchange of genetic materials between Chromosomes 9 and 22, leading to the formation of abnormal gene. More often than not, this condition results in cancer.
Lebers Optic neuropathy
Myoclonic epilepsy with Ragged red fibers
Mitochondrial encephalopathy, Lactic acidosis and Stroke like episode.
Wrapping up, this piece encapsulates the most common diseases that everyday people deal with, laying emphasis on the inherited ones. After perusing it, it is believed that you understand why people suffer from certain hereditary diseases. Obviously, hereditary diseases manifest in many different forms and in-depth knowledge of their causes – as explained in this guide – will help the victims get the right medical help.