When is 'I do' taboo?

Ireland has the highest recorded incidence of Hurler syndrome - a genetic disorder potentially fatal among children. Three quarters of Irish children diagnosed with the disorder are Travellers. A screening programme could save lives, yet no such programme is in place. Sandy Hazel investigates one of the risks of 'cousin marriage' in the first of three articles on Traveller health.

Cousin marriages are not exclusive to Irish Travellers. Royal families have practiced strategic couplings for years. The Bible is full of intermarried families. Over a billion people live in areas where 20 to 50 per cent of marriages are consanguineous, including the Middle East, Asia and some American states. Consanguineous means relationship by blood; the vernacular is 'cousin marriage'. It is generally prohibited only if the couple are closer than second or first cousins; different regions have different rules and dispensations depending on religion or law.

Genetic disorders are more common in populations with high rates of consanguineous marriage. Rare recessive disorders can cause a range of problems, such as blindness, deafness, skin diseases, metabolic disorders and neurodegenerative conditions. Some researchers have challenged the claims that interbreeding raises risks of genetic illnesses. 

But what do the statistics mean for the Irish Traveller community, where consanguineous marriage is estimated at 40 per cent? Irish health studies frequently cite consanguinity as being "highly contributory towards the increase of metabolic disease and congenital disease”.

In its review of the national screening programme for inherited metabolic disorders, the HSE states that “consanguinity, common amongst the Irish Travelling community, increases the risk for autosomal recessive disorders, some of which may be inborn errors of metabolism…justifying the need for special screening procedures.” The report states that Irish Travellers are an “at risk” group that merits particular attention with regard to newborn screening testing. However, HSE also says that there has been “a low up-take of post-natal services amongst the Traveller community including newborn screening testing”.

Professor Alan Bittles, Director of the Centre for Human Genetics in Perth, Australia has collated data on infant mortality in children born within first-cousin marriages from around the world. He found an increased risk of death of 1.2 per cent and increased risk of birth defects of 4 per cent among children born to cousins.  

Bittles insists that these figures must be viewed with the social and other benefits of cousin marriage. Some Traveller health advocates consider these to be low risks. The Pavee Point website says that cousin marriages are not harmful and that counselling on health is the best approach. 

Bittles’ research used sample populations larger than the entire population of the Irish Travelling community. Asked if gene mutation could be more frequent when the population was as small as the Irish Traveller community Bittles said this was too simplistic. “It very much depends on the type of mutation, whether it is lethal, and if so at what age,” he said in an interview with Politico.ie. “In general, when a recessive mutation occurs in a numerically small, socially or religiously 'isolated' community which avoids inter-marriage with others, and large family sizes are the norm, a recessive mutation can increase in frequency over successive generations, as appears to be the case with Hurler syndrome in the Travellers,” he said.

Hurler syndrome patients usually stop developing between ages 2 and 4. This is followed by progressive mental decline and loss of physical skills. Language may be limited due to hearing loss and an enlarged tongue. Corneas can become clouded and retinas degenerate. The child may develop a short body trunk and a maximum stature of less than 4 feet. Distinct facial features including flat face, depressed nasal bridge, and bulging forehead become more evident in the second year. By age 2, the ribs have widened and are oar-shaped. The liver, spleen and heart are often enlarged. Feeding may be difficult for some children, and many experience periodic bowel problems. Children with Hurler syndrome often die before age 10.

Research by Dr Sally Ann Lynch from Our Lady's Hospital for Sick Children in Dublin, indicates that the majority of children (73 per cent) diagnosed with Hurler syndrome came from the Irish Traveller population. Overall, Ireland has the highest recorded incidence worldwide.

Lynch's study says that "given the morbidity and mortality associated with delayed treatment, we recommend targeted newborn screening for this population".  In an interview with Politico.ie, Lynch said that every community has its own inherited disorders. "For example, Irish babies have higher than usual incidences of cystic fibrosis and Nigerian babies have higher sickle cell anaemia."  

Lynch explained that neonatal screening for cystic fibrosis is due to start in Ireland later this year. “Once that has been implemented it would be nice to think that a screening programme for Hurler syndrome amongst this at-risk group would be considered,” she added. 

Lynch says that Irish paediatricians are "switched on" to the incidence of Hurler syndrome among Traveller children, and they usually screen babies early. But a neonatal screening programme would identify these babies even sooner. "An early diagnosis means earlier treatment and possible prevention of some of the many complications that this condition can cause". Early treatment involves enzymes, but late diagnosis means bone marrow transplants.

A 2003 report, 'A Community Genetics approach to health and consanguineous marriage in the Irish Traveller community' recommended: 

• non-directive genetic counselling based on a detailed medical history 
• there hsould no major impediment to dispensation for marriage between Traveller couples who are first cousins 
• the preparation of appropriate education and training modules and materials, and 
• additional resources to be made available to the National Centre for Inherited Metabolic Disorders and the National Centre for Medical Genetics 'to allow them to expand their capacity to provide community genetics services to Travellers nationally.

Families from the Traveller population with a relative affected by Hurler syndrome or any other genetic disorder can be referred to the National Centre for Medical Genetics if they are worried about the possible risks to their children. Carrier testing is available for most of the genetic conditions seen amongst the Traveller population including Hurler syndrome.

There is no proactive screening of the Traveller population no more than there is proactive screening of the non-traveller Irish population. Referrals from all sectors of the Irish population are driven either by clinician or patient request. However, some communities are more driven to seek testing and preventative care than others.

Dispensations are required for consanguineous marriage within the Catholic Church. Fr Derek Farrell of the Parish of the Travelling People based in Phibsboro said that each Diocese is independent when it comes to granting dispensations. As part of the couple’s pre-marriage preparation, a discussion on factors relating to such unions and the availability of genetic counselling takes place.

“We can offer a referral, we aim to be a bridge between the couple and the health service, to build a trust,” said Farrell. A recommendation for a dispensation is made by the couple’s priest to the local bishop. But dispensation isn’t automatic said Farrell. Some aren’t granted and some dioceses don’t allow them. Refusals can sometimes lead to a couple travelling to the UK to be married.

While there is sensitivity around the choice to follow through or not on genetic counselling, Farrell said that in his experience there is little take up of the service.