Hyperhomocysteinaemia

Alzheimer-type dementia - Hyperhomocysteinaemia Factor

Definition

The RMA defines hyperhomocysteinaemia to mean "a condition characterised by an excess of homocysteine in the blood".

General information

Homocysteine is an amino acid (one of the chemical compounds that forms proteins). Everyone produces it, mainly from eating animal products.  Normally the substance is converted into other non-damaging amino acids.  If the normal homocysteine disposal systems are faulty then homocystine can form.  This homocystine can then build up in the blood and appear in the urine.

The potential artery-damaging effects of elevated total homocysteine (tHcy) levels were suggested for many years before the substance was finally recognised as a risk factor for atherosclerotic disease.

Hyperhomocystinaemia can be due to inherited enzyme defects, various dietary deficiencies (folate and vitamins B6 and B12) or chronic renal failure.  In its most common form caused by deficiency of the enzyme cystathionine-beta-synthetase, affected individuals are normal at birth, but can develop lens subluxation, lengthening and weakening of long bones, and variable degrees of mental retardation.  These manifest during childhood and adolescence.

The presence of hyperhomocystinaemia is demonstrated by a blood test and would be commented on in the medical records.

Last reviewed for CCPS 16 September 2011.

Preliminary questions [41446]

41484 there is some evidence that hyperhomocysteinaemia may be a factor in the development of the condition under consideration.

41486 the veteran had hyperhomocysteinaemia at some time.

41425  the veteran has established the causal connection between the hyperhomocysteinaemia and VEA service for the clinical onset of Alzheimer-type dementia.

41487   the veteran has established the causal connection between the hyperhomocysteinaemia and operational service for the clinical onset of Alzheimer-type dementia.

or

41488   the veteran has established the causal connection between the hyperhomocysteinaemia and eligible service for the clinical onset of Alzheimer-type dementia.

Clinical onset and operational service [41487]

41489 the veteran had hyperhomocysteinaemia at least 10 years before the clinical onset of Alzheimer-type dementia.

7992     the hyperhomocysteinaemia is causally related to operational service.

Clinical onset and eligible service [41488]

41489 the veteran had hyperhomocysteinaemia at least 10 years before the clinical onset of Alzheimer-type dementia.

7993     the hyperhomocysteinaemia is causally related to eligible service.