KBG syndrome is a rare genetic condition impacting multiple bodily systems. Symptoms vary among individuals, even within the same family. Early recognition is important for timely support and intervention.
Defining Physical Traits
Individuals with KBG syndrome often display distinctive physical characteristics. A notable feature is macrodontia of the upper central incisors, where these front teeth appear unusually large. This dental trait is observed in 80-95% of cases.
Beyond dental features, facial characteristics commonly include a broad nasal bridge, widely spaced eyes (hypertelorism), and prominent eyebrows that might grow together (synophrys). Many also present with a triangular face shape, a wide and short skull (brachycephaly), and a long space between the nose and upper lip. These features collectively contribute to a recognizable facial appearance.
Short stature is common, with many individuals shorter than average from birth, and 40-77% remaining below average height. Skeletal anomalies are also frequently observed, such as brachydactyly (unusually short fingers) and abnormalities in the vertebrae and ribs (costovertebral anomalies). Delayed bone age, where bones appear younger than chronological age, is another skeletal finding.
Developmental and Cognitive Features
KBG syndrome frequently involves developmental and cognitive differences. Developmental delays are a consistent feature, affecting motor skills, speech, and language acquisition. Most individuals learn to speak and walk later than typically expected.
Intellectual disability is commonly associated with KBG syndrome, typically ranging from mild to moderate. While prevalent, some individuals may have intelligence levels within the normal range. These cognitive variations can influence daily life and learning experiences.
Behavioral characteristics are also observed in individuals with KBG syndrome. These can include traits consistent with autism spectrum disorder, hyperactivity, and anxiety. Sleep disturbances are another reported behavioral concern. These neurodevelopmental aspects require comprehensive understanding and support.
Associated Health Concerns
Beyond the defining physical and cognitive traits, individuals with KBG syndrome may experience other health issues. Hearing loss is a recognized concern, occurring in approximately 25-31% of affected individuals. This can include conductive, sensorineural, or mixed hearing loss, with recurrent middle ear infections often contributing to conductive hearing loss.
Dental anomalies extend beyond macrodontia, sometimes including crowded teeth, missing teeth (oligodontia or hypodontia), or enamel hypoplasia. Heart defects are also reported in some individuals, with prevalence rates ranging from 9% to 40%. These can involve issues with heart valves and the walls between heart chambers, such as septal defects.
Genitourinary abnormalities, such as undescended testicles (cryptorchidism) in males, have been noted in a proportion of cases. Gastrointestinal issues, including feeding difficulties, vomiting, constipation, and gastroesophageal reflux disease, can also occur, particularly during infancy. Seizures are another less common feature, reported in about 20-50% of individuals, with varying types and responses to treatment.