Secret of a boy who felt no pain

The Pakistani boy and six relatives had mutations in a single gene that left them incapable of experiencing pain, even though their sense of touch was normal. All have suffered severe injuries as a result of not feeling pain, and the performer died on his 14th birthday after jumping from a roof.

Their cases, however, are of huge medical significance and could help millions of people who suffer intractable pain. The discovery of a single gene that can switch painful stimuli on and off without affecting other body systems raises the prospect of a new class of analgesics with none of the side-effects of conventional painkilling drugs. The gene, SCN9A, is responsible for making a protein called a voltage-gated sodium channel, which seems essential to pain perception. In normal people, this protein is found in high concentrations at the end of pain-sensing neurons. When a painful stimulus is felt, the protein amplifies it and excites the neuron, sending an electrical signal to the brain. The mutation disrupts this process, making the sodium channel protein useless. Painful stimuli thus fail to reach the pain-sensing neurons, and no signal is sent to the brain. The discovery, by a team led by Geoffrey Woods of the University of Cambridge, is particularly exciting because the abnormality appears to have no adverse effects in the children with the mutation, apart from the dangers that come with pain insensitivity. This suggests that a drug that blocked the protein’s activity could fight pain without the side effects that are produced by all the main analgesics available today. The findings also raise the prospect that other, smaller variations in the SCN9A gene could influence the way different people have different thresholds of pain tolerance. In the research, published in the journal Nature, Dr Woods’s team identified the mutated SCN9A gene in six related children, who were aged between four and 14 when examined. The performer died before he could be tested, but his mother carried the mutation and Dr Woods believed he had it. They were of normal intelligence and otherwise healthy, and could feel other tactile stimuli such as touch, pressure, temperature and tickling. “All six affected individuals had never felt any pain,” Dr Woods said. “They would bump into things as they didn’t get hurt, they were covered in bruises. They wear out their bodies. Life without pain sounds like a blessing, but it isn’t.” (Source: University of Cambridge : The Times: December 2006.)