It is caused by a defect in the glycine cleavage system (GCS), which is made up of four protein subunits. Each of these four subunits is encoded by a separate gene. Defects in three of these four genes have been linked to glycine encephalopathy. : 790 
There is a fourth unit in the complex, dihydrolipoamide dehydrogenase or GCSL. However, to date there have been no mutations in GCSL found to be associated with glycine encephalopathy. A small percentage of affected individuals do not have detectable mutations in any of the three genes (listed above) that are typically associated with the disease. However, they still show defective glycine-cleavage enzymatic activity. It is thought that these patients may have mutations in the genes encoding one of the cofactors associated with the GCS complex.Defects in the GCS proteins can prevent the complex from functioning properly or can prevent the GCS complex from forming entirely. When the complex is unable to metabolize glycine properly, this causes excess glycine to build up to toxic levels in the bodys organs and tissues. Damage caused by elevated levels of glycine in the brain and cerebrospinal fluid is responsible for the characteristic seizures, breathing difficulties, movement disorders, and intellectual disability.This disorder is inherited in an autosomal recessive pattern. The term "autosomal" signifies that the gene associated with the disorder is located on an autosome. In an autosomal recessive inheritance pattern, two defective copies of the gene (one inherited from each parent) are required in order for a child to be born with the disorder.
Ichthyosis acquisita is a disorder clinically and histologically similar to ichthyosis vulgaris. : 565

Presentation
Associated conditions
The development of ichthyosis in adulthood can be a manifestation of systemic disease, and it has been described in association with malignancies, drugs, endocrine and metabolic disease, HIV, infection, and autoimmune conditions. : 494 It usually is associated with people who have Hodgkins disease but it is also occurs in people with mycosis fungoides, other malignant sarcomas, Kaposis sarcoma and visceral carcinomas. It can occur in people with leprosy, AIDS, tuberculosis, and typhoid fever. See also
Ichthyosis
Confluent and reticulated papillomatosis of Gougerot and Carteaud
List of cutaneous conditions

References


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