It is clinically important to recognize both bipolar disorder (BD) and borderline personality disorder (BPD) in patients seeking treatment for depression, and it is important to distinguish between the two. However, in routine clinical practice, the differentiation remains difficult.

The aim of the study was to illustrate the difficulty in the practice, to distinguish BD and BPD in depressed patients through a case report.

Mr IK 27-year-old, without medicals history. He is a single man with an animated life, professional instability, substance abuse, sensibility in the refusal, a tendency to impulsiveness and a feeling of meaning devoid. He was hospitalized for three consecutive suicide attempts. We found an unstable patient on the psychomotor plan, with depressive humour and anhedonia. The final diagnosis was major depressive episode without signs of bipolarity. He was putted under fluoxetine. The evolution was marked by a turn maniac. Diagnosis of BD and BPD were discussed. Aspect of the BPD appears and confirmed by Rorschach test.

At present the links between BD and BPD remains a subject of controversy. This case suggests that BPD needs to be diagnosed with a narrower set of criteria that cover all of its domains.