Renpenning syndrome is a disorder that almost exclusively affects males, causing developmental delay, moderate to severe intellectual disability, and distinctive physical features. Individuals with Renpenning syndrome typically have short stature and a small head size (microcephaly). Facial features characteristic of this disorder include a long, narrow face; outside corners of the eyes that point upward (upslanting palpebral fissures); a long, bulbous nose with a low-hanging separation between the nostrils (overhanging columella); a shortened space between the nose and mouth (philtrum); and cup-shaped ears. Males with Renpenning syndrome generally have small testes. Seizures and wasting away (atrophy) of muscles used for movement (skeletal muscles) may also occur in this disorder.