

KOLKATA: A rare thalassaemia gene mutation that could be specific to Bengali Brahmins has been detected by researchers in Kolkata.

The 'Fannin Lubbock' mutation is a silent one, which cannot be detected in regular thalassaemia screening and has so far only been traced in a group of thalassaemia carriers in the Mediterranean region of Europe.

What the discovery means is that unwitting carriers of the gene can now get a confirmatory test so that they don't end up marrying another carrier and putting their child at risk of this deadly disease. A team of experts under the guidance of senior scientist Jayasree Basak is researching the mutation and its origin.

Fannin Lubbock mutation had not been reported from anywhere else in the world till scientists at Netaji Subhas Chandra Bose Cancer Research Institute ( NCRI ) chanced upon four thalassaemia carriers of a single family in Bandel last month.

The three women and a child had the rare mutation. Since no member of the family - a conservative Brahmin one belonging to the Barendra sect - has ever married outside the caste, scientists are intrigued about the source of the mutation and a study has been launched.

Fannin Lubbock mutation alters the beta globin gene structure in haemoglobin and is impossible to detect in blood count tests. It's only revealed on molecular analysis. The defect doesn't lead to thalassaemia. It merely makes the person a carrier but a child of two thalassaemia carriers has a 25% chance of being born with the ailment.

The discovery of the gene in the Barendra sect was almost by accident. A female member of the family visited NCRI for treatment after she had post-natal complications and a low haemoglobin count. While regular tests didn't show anything abnormal, molecular analysis revealed an alteration in the haemoglobin structure.

"It was strikingly similar to Fannin Lubbock that has so far been detected only in Europe. We compared her mutation to the past cases and found that the origin was not the same," said Deboshree M Bhattacharyya, a senior research fellow at NCRI.

Intrigued, the researchers launched into an intensive study. They screened all 16 members of the family and studied their clinical history. "We were surprised to find that the woman's mother was a carrier and had the mutation, too. Her aunt had Fannin Lubbock as well and she passed on the gene to her young son. We are trying to trace the source of the gene since it has never been reported anywhere in the sub-continent, let alone Bengal," said Jayasree Basak.

It's all the more intriguing since a very small percentage of Bengali Brahmins are thalassaemia carriers, compared to the rest of the Bengali population, she added.

Around 2-3% of Bengali Brahmins are carriers, compared to 10-11% of the non-Brahmins. "This particular family hasn't had an inter-caste marriage in at least four generations. So, the source remains a mystery. Non-Brahmins in Bengal have a higher percentage of thalassaemia carriers because they marry outside the caste more often," said Deboshree Bhattacharyya.

Bengal now has more than 1 lakh thalassaemia patients and 10% of the population in Kolkata is believed to be carriers. Secretary of the Thalassaemia and Aids Prevention Society Sailen Bose, however, refused to accept that thalassaemia could be caste-specific. "It would be wrong to conclude that fewer Brahmins have the disease since there has been no authentic study. Irrespective of caste, the number of thalassaemia patients has been spiralling. If this latent gene is detected it would be a boon. Or else carriers would go undetected," said Bose.

