A rare massive presentation of catamenial hemothorax.

Catamenial hemothorax is a rare manifestation of thoracic endometriosis syndrome. It is commonly seen associated with pelvic endometriosis in nulliparous reproductive-age women. Most cases are minor and self-limiting. We present a case of a 32-year-old woman who presented with prolonged worsening dyspnea and was found to have a massive hemothorax on evaluation.