Genome Study in Constitutional Thinness

Study Overview
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Brief Summary
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Constitutional thinness (CT) is a recently defined entity as a differential diagnosis of anorexia nervosa (AN), considered to be the most frequent cause of low body mass index (BMI) in young women. CT subjects present no AN psychiatric traits, preserved menses, no biological signs of undernutrition and balanced energy metabolism despite a Body Mass Index (BMI) <17 kg / m². CT familial aggregation, low body mass without a hormonal explanation, and specific appetite regulation profile suggest a specific genetic profile in these subjects. Objective: A family linkage study in order to identify genes involved in the constitutional thinness phenotype by using genome wide scan (GWAS) techniques Studied population: Fifty families including at least one well phenotyped CT index case (grade 2 or 3 of thinness according WHO classification). Blood or saliva is sampled for DNA extraction. Perspectives: Revealing eventual abnormalities could lead to a more precise diagnosis of constitutional thinness and new hypothesis in understanding extreme bodyweight mechanisms.

Official Title
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Genome Study in Constitutional Thinness

Conditions
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Thinness, Leanness

Intervention / Treatment
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* Other: blood or saliva specimen


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: For all subjects: age > 18 yrs affiliation to health insurance member of a family including at least 2 CT members and overall 3 evaluable members over 2 generations written and signed consent For CT subjects : grade 2 or 3 of thinness according WHO classification women, BMI < 17 kg/m² at 20-30 yrs or < 19 for older subjects men, BMI < 18 kg/m² at 20-30 yrs or < 20 for older subjects absence of DSM criteria for anorexia nervosa young women : normal menses and fat mass percentage 15 % ; absence of DSM criteria for anorexia nervosa men : normal testosterone level For subjects without CT : women, BMI > 19 kg/m² men, BMI > 20 kg/m² Exclusion Criteria: CT subjects: smoking > 5 cigarettes / day history of emaciating pathologies intense physical activity > 7 hours / week For all subjects : refuse of written consent

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| CT subjects<br>blood or saliva specimen | Other: blood or saliva specimen<br>* blood or saliva specimen is sampled for DNA extraction in CT family's members<br>|
| subjects without CT<br>blood or saliva specimen | Other: blood or saliva specimen<br>* blood or saliva specimen is sampled for DNA extraction in CT family's members<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| chromosome regions' abnormalities | The linkage study is performed in order to identify one or several chromosome regions linked the constitutional thinness phenotype by using genome wide scan (GWAS) techniques in CT families members. | day 1 | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| genetic markers | Identify within upper mentioned regions more specific genetic markers (mutation/variant) to characterize genes involved in CT phenotype | day 1 | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Constitutional Thinness, linkage study, genome wide scan (GWAS)