RESUMEN
The genetic transmission of bipolar disorder remained undetermined up to now, partly due to clinical and genetically heterogeneity. In Tunisia, genetic study will profit from the existence of high rates of consanguinity. To determine the rate of consanguinity in bipolar I disorders sample and to compare the clinical characteristics and the frequency of affective disorders in first and second degree relatives of probands with and without consanguinity. One hundred thirty subjects met DSM-IV criteria for a bipolar I disorder were recruited. Available Information was obtained from a structured clinical interview, collateral history and medical records. The family investigation allowed completion of genealogies over three generations. The comparison was based on the clinical characteristics [age of onset, numbers of affective episodes, nature and severity of the last affective episode] and the frequency of affective disorders in first and second degree relatives of probands with and without consanguinity. The rate of consanguinity was estimated to 28, 5%It was higher in patients with family history of affective disorders: 34, 2%versus 20, 4%[p=0, 08]. Bipolar I patients with consanguinity were characterised by a high frequency of affective episodes and a more severe of the last affective episode, but theses differences were not significantly. However, the frequency of affective disorders was significantly increased in first degree relatives of probands with consanguinity: 10, 5%versus 6, 1%[p=0, 01], and in first and second degree relatives of probands with consanguinity: 4, 5%versus 2, 9%[p=0, 02]. The influence of consanguinity on the clinical characteristics and the frequency of affective disorders in first and second degree relatives of bipolar patients is en favour the recessive polygenetic transmission of bipolar disorders