A roux darkening on the stovetop, andouille and crawfish cooking away with the trinity of green bell pepper, onion, and celery in a pan nearby. Rich and reedy accordion music filling the heavy bayou air as a breeze passes lazily through cypress trees and Spanish moss. A dash of Tony Chachere to bring it all together. For many, the term ‘Cajun’ evokes romantic scenes of rural Louisiana life. In the world of genetic counseling, however, ‘Cajun’ represents a distinct and often overlooked American ethnic group.
‘Cajun’ derives from ‘Acadian,’ or French-Canadian and Catholic residents of Nova Scotia, which were expelled from the region in the mid-1700’s. The exiled population eventually settled in communities along the Mississippi River near the Lafource, Teche, and Vermillion Bayous, where they have remained for over two centuries. Once a pejorative term used to refer to individuals with French ancestry and poor economic standing, the term ‘Cajun’ has been largely reclaimed as a self-identification, a place name, and an ancestral designation. At present, there are an estimated half million Acadian descendants living in Louisiana, with perhaps a hundred thousand people still speaking some Cajun-French in the home (Cleaver, 2020). For the Cajun people, laissez les bons temps rouler! Let the good times roll!
The insular and exiled nature of the original Acadian bayou communities resulted in the preservation of the cultural heritage of the Louisiana Cajuns, celebrated around the world for their language, cuisine, and music. However, the relative isolation of these populations led to other profound consequences for their modern descendants: common genetic inheritance and an increased predisposition for genetic disease.
One of the first genetic disorders identified at high rates in the Cajun population was Friedreich Ataxia, a progressive neurodegenerative disorder typically resulting from autosomal recessive inheritance of a trinucleotide repeat expansion. In the United States, an estimated 1 in 40-50,000 individuals are diagnosed with Friedreich Ataxia; studies initiated in the 1980’s found that number increases to 1 in 20,000 amongst individuals with Cajun ancestry (Siguro, 1992; Guidry, 2014).
Another autosomal recessive disorder disproportionately affecting Cajuns was identified in the following decade: Usher syndrome, specifically type 1C. The so-called Usher syndrome “Acadian Allele,” or USH1C c.216G>A, has been identified as a founder mutation in French-Canadian Acadians as well as Cajuns in southern Louisiana (Ebermann, 2007). Usher syndrome is so prevalent in Cajun communities that it has had an impact on American Sign Language; the ASL dialect used in southern Louisiana borrows from tactile ASL and restricts signing to a smaller physical space (Baudoin Griffard, 2017).
Additional rare autosomal recessive disorders have been identified in Louisiana Cajuns, attributed to Acadian founder effects. Two different recurrent HEXA mutations resulting in Tay-Sachs have been identified in Cajuns; the four pair (TATC) insertion in exon 11 of the HEXA gene has been traced back to a single ancestral couple over two hundred years ago (McDowell, 1992). Carrier frequency for disease-causing HEXA mutations amongst Cajuns is similar, or greater, than rates observed amongst Ashkenazi Jewish populations. In one rural community called Iowa (pronounced Eye-oh-way), the carrier frequency is higher than 1 in 10. Tay-Sachs is so prevalent in the region that it is known colloquially as “the Cajun disease.” Written records and oral history from early Cajun settlements describe “lazy baby” disease where apparently healthy infants would decline and die in early childhood; perhaps the legacy of undiagnosed Tay-Sachs (Kennedy, 1990).
Autosomal dominant disorders have also been identified at elevated frequency in Cajun populations. Louisiana has an increased prevalence of Charcot-Marie-Tooth disease type 1A due to PMP22 duplications (Guidry, 2014) as well as oculopharyngeal muscular dystrophy due to a Cajun PABP2 founder mutation (Scacheri, 1999).
From a genetic counseling perspective, the Cajun population represents a unique cultural and ancestral community with unique needs in preconception and clinical counseling. However, the need for such services is far outpaced by the current workforce. Many studies addressing the unique genetic background of this population are outdated. Louisiana hereditary disease centers are underfunded and underutilized. Currently, there are six clinical genetic counselors in Louisiana, supporting a population of over four million residents. C’est tout. That’s all.
Ultimately, the Cajuns of Louisiana provide a reminder of the importance of understanding the unique ethnic and ancestral populations we encounter in professional practice. We are better prepared to serve the patients by taking time to engage with the history, origins, and identity of these communities.. And for all of us, ça c'est bon! That’s good!
Baudoin Griffard, P. (2017, Summer). Cajun Strong: Advances in genetics provide new hope for Acadiana’s close-knit population of Usher's syndrome carriers. 64 Parishes. https://64parishes.org/cajun-strong.
Cleaver, M. (2020, October). What's the difference between Cajun and Creole – or is there one? The Historic New Orleans Collection. https://www.hnoc.org/publications/first-draft/whats-difference-between-cajun-and-creole-or-there-one.
Ebermann, I., Lopez, I., Bitner-Glindzicz, M., Brown, C., Koenekoop, R. K., & Bolz, H. J. (2007). Deaf blindness in French Canadians from Quebec: a predominant founder mutation in the USH1C gene provides the first genetic link with the Acadian population. Genome Biology, 8(4), R47. https://doi.org/10.1186/gb-2007-8-4-r47.
Guidry, M. (2014, Summer). Guédry & Petitpas Family: Acadian Genetic Diseases. Generations: Les Guédry d’Asteur. http://freepages.rootsweb.com/~guedrylabinefamily/genealogy/acadian_genetic_diseases.html.
Kennedy, J. M. (1990, November). A Tragic Legacy: Why is Tay-Sachs, a rare genetic disorder, killing so many children in a tiny Cajun town? The answer seems to lie in the region’s melting-pot heritage. Los Angeles Times. https://www.latimes.com/archives/la-xpm-1990-11-06-vw-4146-story.html.
McDowell, G. A., Mules, E. H., Fabacher, P., Shapira, E., & Blitzer, M. G. (1992). The presence of two different infantile Tay-Sachs disease mutations in a Cajun population. American Journal of Human Genetics, 51(5), 1071–1077.
Scacheri, P. C., Garcia, C., Hébert, R., & Hoffman, E. P. (1999). Unique PABP2 mutations in "Cajuns" suggest multiple founders of oculopharyngeal muscular dystrophy in populations with French ancestry. American Journal of Medical Genetics, 86(5), 477–481.
Sirugo, G., Keats, B., Fujita, R., Duclos, F., Purohit, K., Koenig, M., & Mandel, J. L. (1992). Friedreich ataxia in Louisiana Acadians: demonstration of a founder effect by analysis of microsatellite-generated extended haplotypes. American Journal of Human Genetics, 50(3), 559–566.