AT THE age of 50, Roger Keyte visited a doctor complaining of months of intermittent stomach ache and diarrhoea, expecting a relatively benign diagnosis such as irritable bowel syndrome.

To his surprise, the cause turned out to be a genetic disease he had never heard of - haemochromatosis, a potentially lethal condition in which the body fails to regulate iron properly.

"It is the most common genetic disorder worldwide, yet many GP s are still unaware of it," says Prof Monique Zaahl, a human geneticist at the University of Stellenbosch.

"Doctors treat patients for diabetes or cardiovascular disease and don't realise that an iron-loading disorder is the underlying condition," she says.

The irony is that once haemochromatosis is detected, the treatment is cheap and simple - bloodletting. Beloved by quacks, charlatans and well- intended doctors from ancient to surprisingly recent times, bloodletting to rid the body of disease eventually fell out of favour as doctors realised that illnesses were spread by germs, and that removing pints of blood from sick patients more often than not made them worse.

However, it remains a vital procedure for patients with iron- loading disorders. As the patient's body makes new blood to replace that which has been removed, it dilutes the iron concentration and brings it back to safe and healthy levels.

Hereditary haemochromatosis is caused by defects in the genes that regulate the way the body absorbs, transports and stores iron, and so the patient absorbs too much of this essential mineral from their diet. The excess gets dumped in organs such as the pancreas, heart, liver or joints and can cause cancer, diabetes, cardiovascular disease and even arthritis.

The disease is an autosomal recessive one: a person needs to inherit a copy of the defective gene from each parent to get the disease; if they have just one copy they will be a silent carrier.

About one in six South Africans of Caucasian descent is a carrier of hereditary haeomochromatosis and about one in 120-150 has two copies of the faulty genes that can result in illness, according to Mr Keyte, the spokesman for the Gauteng branch of the Haemochromatosis Society of SA.

Data on other population groups are more sketchy, partly because for many years scientists believed iron-loading disorders among black Africans were caused by the iron pots used for brewing beer, and so they never thought to investigate the hereditary aspects, says Prof Zaahl.

It now turns out that what was once called "Bantu siderosis" is in fact an iron-overload disorder caused by mutations in a gene responsible for making ferroportin. Ferroportin is involved in transporting iron from the small intestine to the bloodstream - if it fails to do its job properly, the iron is stored in the cells of the liver, spleen and bone marrow. In some parts of the country as many as one in 10 people are affected by the condition, she says.

Despite the fact that a simple genetic test can identify those most at risk of developing iron- loading disorders, all too often the condition is only detected once irreparable damage has set in, and patients are already undergoing treatment for its complications, says Prof Zaahl.

As the excess stored iron accumulates very slowly, the disease typically manifests in middle age - after 40 in men, and a little later in women as the protective benefits of menstruation wane after menopause.

"Sadly, genetic tests are the only way to diagnose people before they have symptoms, but they are costly," says Prof Zaahl. Prices range between R725 and R1300, and not all medical schemes will foot the bill.

Manie de Klerk, the executive manager for clinical best practice at Metropolitan Health subsidiary Qualsa, is finalising guidelines on genetic testing for the schemes in the stable, which account for about a third of SA's medical scheme members. The guidelines are likely to recommend that schemes pay for a selection of genetic tests, provided they have been recommended by a genetic counsellor.

Mr Keete says the lack of awareness of iron-loading disorders among doctors in SA is a huge challenge. The seminars and lectures he organises often prompt doctors to reassess patients. They have often been prescribing iron supplements to patients complaining of fatigue, a potentially dangerous scenario for anyone who is not regulating the mineral properly.