Hypotonia, Ataxia and Delayed Development Syndrome
Autosomal dominant
HADDS is caused by a change in one copy of EBF3, a gene that controls the development of nerve cells, or by a deletion at 10q26 that includes it. Most cases arise de novo.
Signs and symptoms
Low muscle tone, delayed walking, poor balance and coordination, and developmental and speech delay are typical, with intellectual disability ranging from mild to severe. Autistic or behavioural problems and subtle facial features are common. Genitourinary differences, such as vesicoureteral reflux and bladder dysfunction, have been reported in many people, and bowel problems can occur.
What a diagnosis changes
Physiotherapy, occupational and speech therapy, and educational support are central, with eye assessment and kidney and urinary tract evaluation. Most cases arise de novo, but a parent can carry the change, sometimes in only some of their cells, so genetic counselling and parental testing guide recurrence risk.
Genes analysed
Also known as
developmental delay-ataxia-hypotonia-facial dysmorphism syndrome; EBF3 neurodevelopmental disorder; HADDS; hypotonia, ataxia, and delayed development syndrome; HADDS
