Primary clinical features include infantile feeding difficulties often requiring assisted feeding techniques. The majority of affected individuals present with microcephaly, though this is not a universal feature and may depend on the type of mutation.
Cognitive and behavioural characteristics are frequently seen in the TRIO-associated disorders. The majority of affected individuals experience developmental delay affecting both the speech as well as the motor development. Intellectual disability is part of clinical phenotype, with many affected patients reported to be in the mild intellectual disability spectrum and others in the borderline/normal IQ range.
Several of the patients have been diagnosed with attention deficit / hyperactivity (ADHD) or similar disorder. Stereotypic behaviours and autistic traits may be seen in association with the disorder and a few of the individuals published in the literature showed aggressive behaviour.
Minor hand anomalies are seen in many of affected individuals and consist of short tapering fingers (or brachydactyly), swelling of the proximal interphalangeal joints and on some occasions clinodactyly of the fifth finger. Further orthopaedic problems including kyphosis or scoliosis have been described in few of the patients.
There seems to be no consistent facial phenotype associated with TRIO mutations reported although some individuals may have facial asymmetry and a small jaw with dental anomalies including dental crowding or delayed dentition.