In your response you must comment on the neurobiological basis for the disorder that your classmate has described as well as at least one current and relevant research study related to diagnosis or treatment of the disorder.
1st Respond Peluso
Phenylketonuria is a hereditary neurological disorder caused by the absence of an enzyme that converts the amino acid phenylaline to tyrosine. The accumulation of phenylaline causes damage within the structure of the brain unless a special diet is implemented soon after birth. This disorder can result in severe mental retardation with an average IQ of 20 by six years of age. (Carlson, N. R.) The consumption of food containing phenylaline by infants with PKU has been shown to result in irreversible neuological damage. This often results in microcephaly, motor impairments, choreoathetosis , tremors and skin abnormalities. (Christ, S. E.)
The knowledge within the field of neurology regarding this disorder is incomplete at best, However, research has confirmed that disruption of phenylaline metabolism results in decreased levels of tyrosine as well as the increased levels of phenylaline and associated substances in the blood supply of people with this disorder. Very high levels of phenylaline and its related metabolites including phenypyrufic acid have been shown to cause neuronal injury to take place under certain circumstances. These substances may even play a role in the disruption of the central nervous system. Thus, PKU may result in lower than normal levels of associated neurotransmittors within the structure of the brain. (Christ, S. E.)
PKU can be treated by placing the infant on a low phenylaline diet immediately after birth. This is done in order to keep the phenylaline at the appropriate level in order for myelination of the central nervous system to take place at a normal rate. There is evidence that indicates that adults with previously undiagnosed PKU can benefit from this sort of treatment strategy. There are studies that indicate that by providing a low phenylaline diet for individuals with PKU and other severe cognitive disabilities can often minimize the effects of this disorder. (Fitzgerald, B., Morgan, J., Keene, N., Rollinson, R., Hodgson, A., & Dalrymple-Smith, J.)
Carlson, N. (2013). Physiology of Behavior. Eleventh Edition. Pearson Group.
Christ, S. E. (2003). Asbjorn Folling and the Discovery of Phenylketonuria. Journal of the History of Neuroscience. Vol. 12. No. 1.
Fitzgerald, B., Morgan, J., Keene, N., Rollinson, R., Hodgson, A., & Dalrymple- Smith, J. (2000). An investigation into diet treatment for adults with previously untreated phenylketonuria
and severe intellectual disability. Journal of Intellectual Disability Research.
Alexander disease is a unique type of Leukodystrophy in which there is destruction of the myelin. The myelin is a fatty covering that insulates nerve fibers and promotes rapid transmission of nerve impulses (Ashrafi, 2013). When this covering experiences damage, neurological effects begin to happen. Quinlan (2007), also points out abnormal protein deposits known as Rosenthal Fibers as an indication in Alexanders disease.
Symptoms of this neurological disorder include an enlarged head and brain size, seizures, stiffness in arms and/or legs, intellectual disability and developmental delays (Ashrafi, 2013). Patients will often be born with all of the proper function and will begin to show these signs as the myelin begins deteriorating.
Alexander disease can be diagnoses by clinical evaluation paired with MRI that will show the myelin and will continue to show changes in this area. Identification of heterozygous pathogenic variants in GFAP (glial fibrillary acidic protein) will also show that a patient is suffering from this (Quinlan, 2007).
Alexander disease is terminal and generally takes the patient’s life within 10 years of onset. Therefore, treatment is considered to only be supportive and used to maintain the best quality of life as possible. Nutrition care is often a concern as patients begin to lose the ability to feed themselves and must be tube fed. Patients often take medications for infections and seizure control.
Ashrafi, M., Tavasoli, A., Aryani, O., Alizadeh, H., & Houshmand, M. (2013). Alexander Disease: Report of Two Unrelated Infantile Form Cases, Identified by GFAP Mutation Analysis and Review of Literature; The First Report from Iran. Iranian Journal Of Pediatrics, 23(4), 481-484.
Quinlan, R. A., Brenner, M., Goldman, J. E., & Messing, A. (2007). GFAP and its role in Alexander Disease. Experimental Cell Research, 313(10), 2077–2087. http://doi.org/10.1016/j.yexcr.2007.04.004