Overview
Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome is a rare genetic brain disorder. The name describes its main features: a head that grows more slowly than normal after birth (postnatal microcephaly), weak muscle tone in infancy (infantile hypotonia), stiffness and spasticity mainly in the legs (spastic diplegia), difficulty speaking clearly (dysarthria), and intellectual disability. This condition is sometimes referred to by its Orphanet code ORPHA:477673 or linked to the ICD-10 classification G11.4, which covers hereditary spastic ataxias and related disorders. The syndrome affects the developing brain and nervous system. Children are typically born appearing normal in head size, but the head grows more slowly than expected in the months and years after birth. Over time, the brain changes lead to tight, stiff leg muscles that make walking difficult, weak muscle tone in early infancy, and challenges with speech and learning. The degree of intellectual disability can vary from mild to more severe. There is currently no cure for this condition. Treatment focuses on managing symptoms and improving quality of life. This includes physical therapy to help with movement and muscle stiffness, speech therapy to improve communication, and educational support tailored to each child's learning needs. Some children may benefit from medications to reduce muscle spasticity. Early intervention and a strong support team can make a meaningful difference in a child's development and daily life.
Key symptoms:
Head that grows more slowly than normal after birth (postnatal microcephaly)Floppy or weak muscle tone in infancy (hypotonia)Stiff, tight leg muscles causing difficulty walking (spastic diplegia)Slurred or unclear speech (dysarthria)Intellectual disability ranging from mild to severeDelayed motor milestones such as sitting, standing, and walkingDelayed speech and language developmentDifficulty with balance and coordinationPossible feeding difficulties in infancy
Clinical phenotype terms (22)— hover any for plain English
Autosomal recessive
Passed on when both parents carry the same gene change; often skips generations
Infantile
Begins in infancy, roughly 1 month to 2 years old
Treatments
No FDA-approved treatments are currently listed for Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome.
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Specialists
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Treatment Centers
8 centersBaylor College of Medicine Rare Disease Center ↗
Baylor College of Medicine
📍 Houston, TX
🏥 NORDStanford Medicine Rare Disease Center ↗
Stanford Medicine
📍 Stanford, CA
🔬 UDNNIH Clinical Center Undiagnosed Diseases Program ↗
National Institutes of Health
📍 Bethesda, MD
🔬 UDNUCLA UDN Clinical Site ↗
UCLA Health
📍 Los Angeles, CA
🔬 UDNBaylor College of Medicine UDN Clinical Site ↗
Baylor College of Medicine
📍 Houston, TX
🔬 UDNHarvard/MGH UDN Clinical Site ↗
Massachusetts General Hospital
📍 Boston, MA
🏥 NORDMayo Clinic Center for Individualized Medicine ↗
Mayo Clinic
📍 Rochester, MN
👤 Mayo Clinic Center for Individualized Medicine
🏥 NORDUCLA Rare Disease Day Program ↗
UCLA Health
📍 Los Angeles, CA
Travel Grants
No travel grants are currently matched to Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome.
Community
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Caregiver Resources
NORD Caregiver Resources
Support, advocacy, and financial assistance for caregivers of rare disease patients.
Mental Health Support
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Family & Caregiver Grants
Financial assistance programs specifically for caregivers of rare disease patients.
Social Security Disability
Learn how rare disease patients may qualify for SSDI/SSI benefits.
Questions for your doctor
Bring these to your next appointment
- Q1.What genetic testing do you recommend to find the exact cause of my child's condition?,What therapies should we start right away, and how often should my child receive them?,Are there any medications that could help with my child's muscle stiffness?,What developmental milestones should we realistically expect, and how can we support progress?,What signs should prompt us to seek emergency care?,Are there any clinical trials or research studies we should know about?,What support services and educational resources are available for our family?
Common questions about Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome
What is Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome?
Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome is a rare genetic brain disorder. The name describes its main features: a head that grows more slowly than normal after birth (postnatal microcephaly), weak muscle tone in infancy (infantile hypotonia), stiffness and spasticity mainly in the legs (spastic diplegia), difficulty speaking clearly (dysarthria), and intellectual disability. This condition is sometimes referred to by its Orphanet code ORPHA:477673 or linked to the ICD-10 classification G11.4, which covers hereditary spastic ataxia
How is Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome inherited?
Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome follows a autosomal recessive inheritance pattern. Genetic counseling can help families understand recurrence risk and testing options.
At what age does Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome typically begin?
Typical onset of Postnatal microcephaly-infantile hypotonia-spastic diplegia-dysarthria-intellectual disability syndrome is infantile. Age of onset can vary across affected individuals.