Isolated lissencephaly type 1 without known genetic defects belongs to the genetically heterogeneous group classic lissencephaly (see this term). 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.
Data from Orphanet are used to provide information on a disease's name, synonym(s), and overview. Reference: Access aggregated data from Orphanet at Orphadata. Orphadata: Free access data from Orphanet. © INSERM 1999. Available on http://www.orphadata.org. Data version April 2026
Newly diagnosed with
Isolated lissencephaly type 1 without known genetic defects?
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Advocacy Organizations
Genetic Epilepsy Team Australia
Collaboration of research and care
PPP2CA Pathways
PPP2CA Pathways connects families, shares strength, and supports the research community in the search for answers to Houge-Janssens Syndrome type 3.
Rare Epilepsy Network (REN)
Improving outcomes of people with rare epilepsies through an innovative collaborative infrastructure that drives urgent, patient-centered research, educaiton and advocacy.
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Clinical Trials
For a list of clinical trials in this disease area, please click here.