1. Homocystinuria
By Sean Burke

2. A person who is heterozygous for a mutation in CBS or in MTHFR will generally have mild increases in homocysteine levels. There is another type of mutation that can occur with MTHFR. This mutation results in a thermolabile variant (that means that the protein becomes inactivated with heat). A patient who is heterozygous for this mutation has no evidence of hyperhomocysteinemia or increased risk of thrombotic disorders. Patients who are homozygous for the defect can develop hyperhomocysteinemia. In addition to the above causes, deficiencies in Vitamin B6 and folate can lead to increased levels of homocysteine. Other causes include certain medications and kidney disease.

3. MS requires vitamin B12 (methylcobalamin) in order to carry out its reaction. If a patient does not have an adequate supply of vitamin B12, then homocysteine is not converted to methionine and the net result is an increase in homocysteine

4. MTHFR is required to form 5-methyl tetrahydrofolate (as depicted above). This is required in order to convert homocysteine to methionine. If this can not be formed, then homocysteine levels will increase.

5. The final enzyme associated with elevated homocysteine levels in CBS; this is required in order to convert homocysteine to cysteine. If this enzyme is not present, then homocysteine levels will increase

6. What is affected? Brain: Risk of developing mental retardation.
Eyes: Neartsightedness, Dislocation of lens at front of eye.
Blood: Risk of abnormal bloodclotting.
Bones: risk of osteoporosis and other skeletal abnormalities

7. Age?
People can be born with the disease but many may not show symptoms and may not even develop problems because they are taking the right measures.

8. Connection
I am connected to this disease because my Grandmother’s brother has mental disabilities due to the protein deficiency.

9. Chart

10. Works Cited
Homosystinuria. (2014, January 13). Retrieved from (n.d.). Retrieved from
(n.d.). Retrieved from
Dr. Gurvinder, R. (2013, June 13). Retrieved from