A rare presentation of isolated right-sided pleural effusion
• The occurrence of unilateral right-sided pleural effusion without ascites may be an atypical course of ovarian hyperstimulation syndrome.

• Primary prevention when performing ovarian stimulation should be taken into consideration in order to avoid ovarian hyperstimulation syndrome.

• Ovarian hyperstimulation syndrome is an iatrogenic and potentially life-threatening condition that must be diagnosed and treated promptly.

Ovarian hyperstimulation syndrome (OHSS) is usually an iatrogenic disorder. The incidence of moderate to severe OHSS is 1–5% of all in vitro fertilization (IVF) cycles, with a mortality rate of 1:45000–1:50000. Most cases of OHSS arise only 2–7 days after oocyte pickup (OPU) due to the administration of exogenous human chorionic gonadotropin (hCG) on the day of ovulation induction, a so-called “early-onset OHSS.” A decline in serum hCG concentration 7–10 days after hCG-induced ovulation leads to improved OHSS symptoms. In contrast, “late-onset OHSS” occurs 12–17 days after hCG administration almost exclusively due to endogenous hCG production resulting from pregnancy. A 38-year-old woman who had undergone in vitro fertilization presented with OHSS. Six days after transvaginal oocyte pickup, she presented with only an isolated right-sided pleural effusion and restricted respiratory capacity. A thoracentesis was successful. Clinicians must be aware of unilateral pleural effusion, with a higher incidence on the right side, as a single-symptom presentation of OHSS. The case reported here illustrates the diversity and severity of OHSS.