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Start free with EleplanIsolated lissencephaly type 1 without known genetic defects
ORPHA:1084Disease
What it is
Isolated lissencephaly type 1 without known genetic defects belongs to the genetically heterogeneous group, classic lissencephaly. It is a diagnosis of exclusion, when neither associated malformations nor family history are present, and in the absence of mutations of genes known to be involved in classic lissencephaly. Clinically patients present with the common features of classic lissencephaly such as developmental delay, intellectual disability, and seizures.
Key facts
- Age of onset
- Infancy, Neonatal
- Inheritance
- Unknown
- Classified as
- Disease
Signs and symptoms
Common30–79%
17- Agyria
- Axial hypotonia
- EEG with changes in voltage
- Enlarged sylvian cistern
- Feeding difficulties
- Gray matter heterotopia
- Hypsarrhythmia
- Infantile spasms
- Intellectual disability, profound
- Intellectual disability, severe
- Motor seizure
- Neonatal hypotonia
- Neurodevelopmental delay
- Pachygyria
- Seizure
- Spasticity
- Ventriculomegaly
These ranges are how often a sign appears across everyone diagnosed, not a prediction for one person — most people have some of these and not others. Orphanet also records findings that are specifically absent in this disease; those are in the data but not listed here.
ICD-10 codes
ICD-10 has no distinct code for most rare diseases, so many are filed under the nearest available one. A shared code identifies the group, not this disease — the ORPHAcode above is what identifies it.
Related health topics
Reached through the ICD-10 categories this disease is filed under, so these describe the broader group rather than this disease specifically.
Cross-references
Orphadata Science: Free access data from Orphanet. © INSERM 1999. Data version 2026-06-23. Available under CC BY 4.0. This is a reference, not medical advice.
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