1) A 12 year old boy complains of achy joints usually after soccer practice

Answer:

What is the role of genes in the development of arthritis?

There is a link between genes and the prevalence of arthritis. Family studies show that a patient is more likely to have arthritis if they have relatives with the disease. Twin studies also show this phenomenon. Identical twins (who share 100% of their genes) were more likely that both of them have arthritis than non-identical twins (share 50% of their genes). In a UK study, their twin study set had 15% prevalence of RA in identical twins than 4% in non-identical twins.

The transmission of arthritis between generations however is not direct as in they are non-mendelian. The environment is also found to be a large factor in the disease. There are currently two genes that are known in the development of Rheumatoid Arthritis, the HLA-DRB1 gene and The protein tyrosine phosphatase 22 gene (PTPN22).

References:

https://www.nras.org.uk/the-genetics-of-rheumatoid-arthritis

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3655138/

https://ghr.nlm.nih.gov/condition/rheumatoid-arthritis#

https://www.webmd.com/arthritis/understanding-arthritis-basics#1

Compare and contrast osteoarthritis and rheumatoid arthritis.

The difference between these two types of arthritis are the cause of the joint deterioration and pain. Osteoarthritis is caused by the mechanical deterioration that happens to the joints that happens during everyday life. In comparison, Rheumatoid Arthritis is an autoimmune disease where the body's immune system detect the joints as a threat and attacks it.