classic lissencephaly isolated lissencephaly type 1 without known genetic defects https://www.malacards.org/card/isolated_lissencephaly_type_1_without_known_genetic_defects SCTID:715406003 icd11.foundation:80358651 UMLS:C4275151 GARD:0018715 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. MONDO:0015205 Orphanet:1084 MEDGEN:895946