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Clinical characteristics. The classic of megalencephalic leukoencephalopathy with subcortical cysts (MLC) is characterized by early-onset macrocephaly, often in combination with mild gross motor developmental delay and seizures; gradual onset of ataxia, spasticity, and sometimes extrapyramidal findings; and usually late onset of mild mental deterioration. Macrocephaly, observed in virtually all individuals, may be present at birth but more frequently develops during the first year of life. The degree of macrocephaly is variable and can be as great as 4 to 6 SD above the mean in some individuals. After the first year of life, head growth rate normalizes and growth follows a line parallel to and usually several centimeters above the 98th centile.

Initial mental and motor development is normal in most individuals. Walking is often unstable, followed by ataxia of the trunk and extremities, then minor signs of pyramidal dysfunction and brisk deep-tendon stretch reflexes. Almost all individuals have epilepsy from an early age. The epilepsy is typically well controlled with medication, but status epilepticus occurs relatively frequently. Mental deterioration is late and mild. Disease severity ranges from independent walking for a few years only to independent walking in the fifth decade.

Some individuals have died in their teens or twenties; others are alive in their fifties. An improving has a similar initial presentation with delayed mental or motor development, followed by an improving clinical course: macrocephaly usually persists, but some children become normocephalic; motor function improves or normalizes; hypotonia and clumsiness may persist in some or neurologic examination may become normal. Some have intellectual disability that is stable, with or without autism. Epilepsy and status epilepticus may occur. The diagnosis of MLC is established in individuals with typical clinical findings and characteristic abnormalities identified on brain MRI examination, including abnormal and swollen cerebral hemispheric white matter and presence of subcortical cysts in the anterior temporal region and often in the frontoparietal region. Identification of pathogenic variants in MLC1 or HEPACAM by can confirm the diagnosis of classic MLC (MLC1 or MLC2A, respectively) – particularly important if clinical features are inconclusive – and allow for family studies.

Identification of a HEPACAM can confirm the diagnosis of MLC with improving (MLC2B) if clinical features are inconclusive, and/or allow for family studies. Genetic counseling.

MLC1 and MLC2A are inherited in an manner. At conception, each sib of an individual has a 25% chance of being affected, a 50% chance of being an asymptomatic, and a 25% chance of being unaffected and not a carrier. Carrier testing for at-risk relatives and for pregnancies at increased risk are possible if both pathogenic alleles have been identified in the family. MLC2B is inherited in an manner. De novo pathogenic variants are common.

Each child of an individual with MLC2B has a 50% chance of inheriting the. Prenatal diagnosis for pregnancies at increased risk is possible if the pathogenic variant has been identified in an family member. Establishing the Diagnosis The diagnosis of MLC is established in a with the above. Flstudio 12 regkeyreg zip file. The characteristic abnormalities on brain MRI examination described in are diagnostic.

Identification of pathogenic variants in MLC1 or HEPACAM by (see ) can confirm the diagnosis of classic MLC (MLC1 or MLC2A, respectively) if clinical features are inconclusive, and/or allow for family studies if the diagnosis has been established based on clinical and characteristic radiographic features. Identification of a HEPACAM can confirm the diagnosis of MLC with improving (MLC2B) if clinical features are inconclusive, and/or allow for family studies if the diagnosis has been established based on clinical and characteristic radiographic features. Molecular genetic testing approaches can include serial single- testing, use of a, and more comprehensive testing. Serial single- testing •. Sequence analysis of HEPACAM can be performed first in individuals with the improving.