Researchers at the University of Leeds have solved the puzzling riddle of "Finger clubbing", which was first identified over 2,000 years ago by Hippocrates.
In fact, scientists have also said that the diagnosis of this condition can now be done by a simple urine test.
Finger clubbing, a deformity of the fingers and fingernails, has long been recognized to be a sign of a wide range of serious diseases, like lung cancer, heart disease, hyperthyroidism, various gastrointestinal diseases. However, the reason behind it was unclear, until now.
"It's one of the first things they teach you at medical school. You shake the patient by the hand, and take a good look at their fingers in the process," Nature quoted Professor David Bonthron of the Leeds Institute of Molecular Medicine, as saying.
He added: "There are benign cases of clubbing, where it isn't associated with other illnesses, but particularly because of the link to lung cancer, it is generally regarded as rather sinister. You look at the range of conditions connected to finger clubbing and wonder what on earth they could have in common."
Thus, the researchers found clues in the medical literature, explaining cases in the past and previous research.
"We knew that in cystic fibrosis patients who have undergone a lung transplant, their finger clubbing goes away. The same goes for empyema patients who have had their lungs drained. It suggested that impaired lung function was somehow crucial to finger clubbing - but we didn't understand how," he said.
For the study, the researchers studied a group of patients suffering from inherited primary hypertrophic osteoarthropathy (PHO), a genetic disorder in which finger clubbing is accompanied by painful joint enlargement and a thickening of the bone.
They then pointed to a fatty compound called PGE2, which is produced naturally by the body to mediate the effects of internal inflammation. After completing its work, PGE2 is broken down by an enzyme 15-HPGD, produced in the lungs.
The researchers found that the patients followed by the Leeds had a genetic mutation, which prevented the production of 15-HPGD, resulting in up to ten times as much of the PGE2 in their systems.
"If you don't have this enzyme the PGE2 isn't broken down normally and simply builds up," said Bonthron.
In case of lung cancer patients, it is the overproduction of PGE2 by the tumour that leads to the clubbing. In congenital heart disease, blood bypasses the lungs, where PGE2 is normally broken down by 15-HPGD.
Tin fact, researchers have said that a simple urine test for levels of PGE2 may help in the diagnosis of unexplained clubbing, and to know if it also has other serious symptoms or not. The results also suggest that existing drugs such as aspirin, which are already used to prevent PGE2 production, may be effective in reducing the painful symptoms of finger clubbing.
The study is published online this week in Nature Genetics.