His right leg had to be amputated above the knee in January after it became gangrenous, followed by his left leg in March. His right hand and lower forearm were removed in August, then his left hand and lower forearm last month.
Brant's legs had caused problems since he was in primary school.
"The leg got really bad in November last year," said Mr Tohu. "He took a bit of a tumble, got an infection in his knee, then it got out of control."
Brant's symptoms were first noticed when he was 6 months old. A rash of purple lesions spread all over his body. Later his fingers and toes were progressively damaged by bouts of constricted blood flow to the extremities, leading to tissue damage and gangrene.
"He hasn't had a whole hand since he was quite young, probably around his primary school years - right through, he's been losing bits of his body," said Mr Tohu.
Like Brant, his sister was diagnosed with systemic lupus erythematosus in childhood, but her symptoms were much less serious, Mr Tohu said.
He said Brant's disease is still progressing.
"He hasn't got a very good outlook. We were told when he was 9 or 10 that 18 years old would probably be the most that we could expect."
This month Brant had a prosthetic fitted by the Artificial Limb Service Auckland clinic to his right arm stump. Another will be made for his left arm once it heals fully. The prosthetic has a hook and clamp mechanism that Brant can operate with his left arm.
"I love my prosthetic," Brant said. "It's really good. It has given me more independence - I can pick up cups, I can hold a fork, I can eat my meals and have a drink."
The next milestone will be reeling in a fish on his uncle Andrew Tohu's boat.
They went fishing on the Whangarei Harbour last month, but Brant was restricted to "just supervising it that time. I would like to catch a fish again".
His father started a Give-A-Little fundraiser but will stop it early after already exceeding the $1000 target by $700.
The money will be used to modify Brant's wheelchair to mount a fishing rod which will have an electric reel with switches big enough for him to operate with his prosthetic; and to pay for a trip on a fishing charter boat.
"Our family has always enjoyed camping, beaching, diving and fishing," Richard Tohu said, "and Brant has been involved as much as possible."
What is systemic lupus erythematosus?
A kind of arthritis. It is an auto-immune disorder in which the body attacks itself.
How many people have it?
In New Zealand there are estimated to be several thousand people. It is more common in women than men; and in Maori and Pacific people than in Europeans.
What causes lupus?
Unknown. A genetic predisposition, linked to a number of genes, may be inherited, but environmental factors could play a role.
What are the symptoms?
There are many, including joint pain, fatigue, fever and poor circulation.
Are there any treatments?
Drugs used include corticosteroids, anti-inflammatories and immune system suppressors. There is no cure.
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