Deanne and Alastair Corps in 2001.

Deanne and Alastair Corps in 2001.

Deanne Corps has lost her son and her mother to a rare disease that may also have taken her brother.

And she now knows that she, too, is at risk from the genetically inherited immune system disorder that has afflicted three generations of her family.

The reach of the disorder through Mrs Corps' family came to light only after the death of her 18-year-old son, Alastair.

He had survived lymphoma, a form of cancer, in childhood, but succumbed to glandular fever at Waikato Hospital in January last year. Acute liver failure was the direct cause of his death, but questions remained.

"Here was this apparently healthy young man who had passed away for causes that they couldn't determine," said Mrs Corps, of Wanganui.

Tests later showed he had the rare immune disorder X-linked lymphoproliferative disease (XLP).

Tests of stored samples then revealed that Mrs Corps' mother, who died of lymphoma in 1991, had the disease, and a check of clinical records showed her brother, who died aged 10 of the same cancer in 1977, probably had the immune disorder too.

XLP is passed on to children by the mother, but until Mrs Corps' mother was found to have died of it, it was thought that only boys developed symptoms.

Now Mrs Corps has to have her immune system monitored carefully for lymphoma.

The Auckland District Health Board laboratory, LabPlus, has developed tests for XLP and two other primary immune deficiency disorders - conditions arising from intrinsic or genetic factors rather than external causes - and is the only New Zealand facility where they are available.

A LabPlus doctor, Associate Professor Rohan Ameratunga, said XLP was so rare it probably affected no more than several families in New Zealand. It could lead to lymphoma, common variable immune deficiency or death from glandular fever.

"[The person's] immune system has a hole. The hole is the glandular fever virus. They can respond to other infections, but not this virus. When they get the virus their immune system falls to bits."

Most people caught the virus by the time they were teenagers. Boys with XLP were usually normal until they caught the virus; once they did, almost all died very quickly.

But if the disorder was identified in boys, they could be cured with a bone marrow transplant, Professor Ameratunga said.