For clinicians
Clinical reference: UPF3B-related disorder.
A rare X-linked recessive condition, formerly Lujan-Fryns syndrome, that can present with intellectual disability, autism-spectrum features, and mild dysmorphism, and is likely underdiagnosed. Below is a quick reference for suspicion, testing, and referral.
- Intellectual disability, often mild to moderate
- Marfanoid habitus
- Hypernasal speech and hypotonia
- Autism-spectrum features not fully explaining the picture
- Maternal male relatives with similar features
- Chromosomal microarray, first tier
- Exome or genome sequencing if microarray is negative
- Texas Medicaid covers exome sequencing for children with unexplained intellectual disability or developmental delay
- Corpus callosum dysgenesis
- Anterior commissure hypoplasia or agenesis
- Olfactory bulb agenesis
- Incomplete hippocampal rotation
- Mild cerebellar atrophy, in a single patient
Neuroimaging findings compiled from Tarpey et al. 2007, Laumonnier et al. 2010, Cherot et al. 2018, and Romano et al. 2024. Brain MRI is available for only a small number of published patients, so these features are not established as typical or expected.
Refer locally.
Local referral pathway for genetics evaluation and testing. Phone and fax to be confirmed directly with the clinic before publication.
A printable, shareable reference for your practice, with a family-facing resource on the back.
Free clinical and family-facing reference, available in multiple languages.
Last updated September 2026.