The review found that only a fraction of the syndromes had been fully studied, and no gene or chromosomal location has been found for more than a quarter of them.
The number of rare genetic conditions that result in obesity appears to be nearly 3 to 4 times what previous reviews have uncovered, according to a new study from Canadian researchers.
Led by senior author David Meyre, PhD, of McMaster University in Hamilton, Ontario, the study searched 7 databases and identifiied 161 papers, from which the team catalogued 79 separate “syndromes” associated with obesity. Previous reviews put the number of such syndromes between 20 and 30. The results were reported in Obesity Reviews.
Only 19 of the 79 genetic syndromes identified in the review have been studied to the point that a lab test could confirm presence in a patient, the authors said. Of the rest, 11 have been partially clarified and 27 have been mapped on a chromosomal region. For more than a quarter (22), scientists have not isolated either the chromosomal location or the gene, meaning much work remains.
While genetic conditions that cause obesity are rare, the study shows how they affect a wider population than previously believed. The health issues that come alongside obesity can be significant, according to Meyre and the study’s first author, Yuvreet Kaur. “Rare genetic forms of obesity with many additional clinical features, such as intellectual disability, facial and organ-specific abnormalities, do exist, Meyre said.
The paper, he said, is a first step toward understanding more about how genes cause these rare syndromes, and how genetic causes affect obesity in the general population. Advances in the study of genetics will speed the next steps, the authors predict.
“With technological advancements in the field of genetics, improved genetic elucidation can potentially identify disease genes for the partially-elucidated and non-elucidated obesity syndromes,” they wrote. “Enhanced clinical research through international collaborations and development of consortia will advance our understanding of the genetic bases and inheritance of syndromic obesity and the biology of human obesity.”
Obesity remains a growing problem world wide and in the United States and Canada.
Kaur Y, deSouza RJ, Gibson WT, Meyre D. A systematic review of genetic syndromes with obesity [published March 27, 2017]. Obesity Rev. 2017; doi: 10.1111/obr.12531.