People assume he's naughty

I have always been fascinated by musicians and medicine, and I found them both in my husband, James. He played the piano beautifully - he is a composer - and looked like Hugh Grant. How could I resist? But, medically, I realised almost immediately that he had Tourette syndrome, a neurological disorder characterised by tics - involuntary, rapid, sudden movements.

At the time, I thought it was both hilarious and endearing. We were married in 1991.

We thought long and hard before having a baby because there was a 50 per cent chance that our child would be born with the syndrome. But we decided the risk was worth taking, and we had Freddy, now 11, and Daisy, eight. I knew instinctively that Freddy had inherited the gene.

Unfortunately, if you inherit the syndrome from your father you tend to get it in the worst possible way. When Freddy was two he had his first tantrum: it started at midday and ended at midnight at the GP's surgery.

One day, he decided he was going to say he didn't like eating chocolate and he kept this up for two years, even though I knew he loved it. When I read to him, he just wanted to race through the whole of something like Winnie-the-Pooh, saying excitedly: "Yes, yes, and then what?"; he couldn't get through books fast enough.

Even with my instincts about it, I cried for weeks when he was formally diagnosed at seven after his primary school asked us to consult an educational psychologist. His head-teacher said: "Freddy prefers to be alone and frequently hides under anything - table, chair, desk - curled up in the foetal position. He finds it difficult to make friends and displays an attitude of superiority, putting down other children and being quite unkind."

The psychologist tested him for four hours and reported an IQ of 144. When this gifted diagnosis was made, I was even more confused, because a lot of the characteristics of gifted children are the same as those with Tourette's. So we had him assessed by a Tourette's expert who confirmed the diagnosis.

So where does being gifted stop and Tourette's start? Being clever and diligent is better and easier for a child than being gifted. Clever children are receptive as opposed to intense; they enjoy their peers rather than preferring the company of adults, as Freddy does. Clever children work hard rather than mess around; they have good ideas rather than wild, silly ones. But gifted children are more interesting company than "ordinary" children. Fred is nearly always in trouble, but he is the greatest company and can be relied upon never to be boring.

James and Freddy have three types of tics: vocal, motor and mental. The vocal tics include making noises, such as dog barks or sometimes random whooping noises - this side of Tourette's is rather fun in our household. Most people who've heard of it think it's all about swearing; that is coprolalia, the inability to suppress rude words, and is only experienced by a small percentage of sufferers. It is impossible to describe the range of motor tics without it sounding like a description of the Ministry of Silly Walks. James has a wonderful sense of humour and he uses this to put people at ease - Tourette's can be alarming if you haven't come across it before. Once, when he was involved in a complicated leg twitch in Tesco, he saw a crowd of grannies staring at him. He smiled broadly and informed them he was fine - he was just auditioning a new twitch. Freddy has a fantastic support in his father, whereas James wasn't diagnosed until he was an adult, and was bullied mercilessly at school.

Even though I am used to it, I still get embarrassed, although I know that's my problem; sometimes, I think I'm a terrible mother to feel ashamed of my own son. I still feel the need to explain the condition to people. Freddy has not yet suffered too overtly with motor tics although we have been through periods of repeated grimacing, eye-rolling, finger-licking and nose-twitching. At the moment, he has taken to spitting, one of the least acceptable of the range of Tourette's twitches. It is never aimed at anyone, and mostly Freddy does it when he thinks no one is watching.

People respond in odd ways to his behaviour. Someone said recently when I asked them to make allowances for Freddy: "Oh, rubbish. How can he have it? He is so beautiful." It is just too awful to accept there's something wrong inside an outwardly beautiful boy. People assume Freddy is simply being mischievous and naughty. And he is such a Jekyll and Hyde character. If I take him out for a meal, I cannot guarantee that he isn't going to ask in a loud voice: "What is this hideous muck?"

At the moment, Freddy is on medication to treat his mental twitches, which include the need to memorise things, such as number plates (very tiring, this one), and obsessive thoughts that his family is dying in a terrible accident. The medication has enabled him to sleep better, and he has stopped ringing from school five times a day to check we are all okay.

I have to make sure Daisy doesn't suffer. My studio at home in Norfolk acts as our sanctuary; Daisy and I have girls' evenings in there; it's our twitch-free zone. Although sometimes I wish Freddy were different, I wouldn't change him for the world. I have cried and will cry buckets over him, but I am also fiercely proud.

Annie Tempest's work can be seen at the O'Shea Gallery, 4 St James's Street, SW1, from 1 November; www.tottering.com.

The Tourette Syndrome (UK) Association: www.tsa.org.uk