In microlissencephaly cases, the primary sulci would be unusually wide and flat while secondary sulci would be missing.At birth, lissencephaly with a head circumference of less than minus three standard deviations (< –3 SD) is considered microlissencephaly.Although genetic diagnosis in patients with MLIS is challenging, exome sequencing has been suggested to be a powerful diagnostic tool. Dobyns-Barkovich classification
In 1999, Dobyns and Barkovich suggested a classification of patients with severe microcephaly combined with gyral abnormalities including: microcephaly with simplified gyral pattern (MSGP), microlissencephaly and polymicrogyria. The classification divided those patients into ten groups in which MSGP represented the first four groups, microlissencephaly referred to the groups from 5-8 and polymicrogyria in the last two groups.In Dobyns-Barkovich classification, Dobyns-Barkovich type 6 is equivalent to Norman-Roberts syndrome (MLIS1) while Dobyns-Barkovich type 8 corresponds to Barth microlissencephaly syndrome (MLIS2). Differential diagnosis
Microlissencephaly is considered a more severe form than microcephaly with simplified gyral pattern. Microlissencephaly is characterized by a smooth cortical surface (absent sulci and gyri) with a thickened cortex (> 3 mm) and is usually associated with other congenital anomalies. Microcephaly with a simplified gyral pattern has too few sulci and normal cortical thickness (3 mm) and is usually an isolated anomaly. Prognosis
Many patients will die within the first year of life. Epidemiology
Microlissencephaly is listed in Orphanet database as a rare disease. There is not much information available about the epidemiology of microlissencepahly in literature.
In approximately 20% of complete moles, the most probable mechanism is that an empty egg is fertilized by two sperm. In both cases, the moles are diploid (i.e. there are two copies of every chromosome). In all these cases, the mitochondrial genes are inherited from the mother, as usual. Most partial moles are triploid (three chromosome sets). The nucleus contains one maternal set of genes and two paternal sets. The mechanism is usually the reduplication of the paternal haploid set from a single sperm, but may also be the consequence of dispermic (two sperm) fertilization of the egg.In rare cases, hydatidiform moles are tetraploid (four chromosome sets) or have other chromosome abnormalities. A small percentage of hydatidiform moles have biparental diploid genomes, as in normal living persons; they have two sets of chromosomes, one inherited from each biological parent. Some of these moles occur in women who carry mutations in the gene NLRP7, predisposing them towards molar pregnancy. These rare variants of hydatidiform mole may be complete or partial. Diagnosis
The diagnosis is strongly suggested by ultrasound (sonogram), but definitive diagnosis requires histopathological examination. On ultrasound, the mole resembles a bunch of grapes ("cluster of grapes" or "honeycombed uterus" or "snow-storm"). There is increased trophoblast proliferation and enlarging of the chorionic villi, and angiogenesis in the trophoblasts is impaired.Sometimes symptoms of hyperthyroidism are seen, due to the extremely high levels of hCG, which can mimic the effects of thyroid-stimulating hormone.