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==Overview==
==Overview==


Galactosemia consists of four types of disorders resulting from abnormal activity of the enzymes involved in galactose metabolism. Type I/ Classical is the most serious form of the disease.
[[Galactosemia]] consists of four types of [[disorders]] resulting from abnormal activity of the [[enzymes]] involved in [[galactose]] [[metabolism]]. Type I/ Classical is the most serious form of the [[disease]].


==Types==
==Types==
===Galactosemia Type 1===
[[Galactosemia]] refers to a group of [[autosomal recessive]] disorders of [[galactose]] [[metabolism]]. They are classified into the following types based on the enzymatic activity <ref name="pmid33562227">{{cite journal| author=Banford S, McCorvie TJ, Pey AL, Timson DJ| title=Galactosemia: Towards Pharmacological Chaperones. | journal=J Pers Med | year= 2021 | volume= 11 | issue= 2 | pages=  | pmid=33562227 | doi=10.3390/jpm11020106 | pmc=7914515 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33562227  }} </ref>
===Type I/Classical===
*Defects in both copies of the [[gene]] that codes for the enzyme [[galactose-1-phosphate uridyl transferase]] or [[GALT]].<ref name="pmid28281081">{{cite journal| author=Coelho AI, Rubio-Gozalbo ME, Vicente JB, Rivera I| title=Sweet and sour: an update on classic galactosemia. | journal=J Inherit Metab Dis | year= 2017 | volume= 40 | issue= 3 | pages= 325-342 | pmid=28281081 | doi=10.1007/s10545-017-0029-3 | pmc=5391384 | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=28281081  }} </ref>.
*Most common and severe form.
**Duarte galactosemia
***Variant of classic galactosemia.
***Galactose metabolised to some extent as GALT not completely absent
***Less severe symptoms than other forms


Galactosemia type 1, also called classic galactosemia is the most common form of the disorder and the first form to be discovered. Individuals diagnosed with classic galactosemia have the genetic makeup G/G, which indicates that they have inherited the galactosemia gene from each parent. They have defects in both copies of the [[gene]] that codes for the enzyme galactose-1-phosphate uridyl transferase or GALT.
===Type II===
*Defect in both copies of the gene that codes for the enzyme galactokinase or GALK.<ref name="pmid15526155">{{cite journal| author=Holden HM, Thoden JB, Timson DJ, Reece RJ| title=Galactokinase: structure, function and role in type II galactosemia. | journal=Cell Mol Life Sci | year= 2004 | volume= 61 | issue= 19-20 | pages= 2471-84 | pmid=15526155 | doi=10.1007/s00018-004-4160-6 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=15526155  }} </ref>
*Less common and harmful than classic galactosemia.
*Does not generally lead to hepatomegaly or brain damage.  


Duarte galactosemia is a variant of the classic galactosemia. Individuals with the genetic makeup D/G have one gene for classic galactosemia from one parent, G, and one Duarte gene variant from the other parent. Individuals with Duarte galactosemia will be able to metabolize some galactose as GALT activity in Duarte Galactosemia patients is approximately 20% to 50%. Patients with Duarte Galactosemia have less severe symptoms than other forms of the disorder.
===Type III===
*Alterations in the [[gene]] coding for [[epimerase]] enzyme.<ref name="pmid16611573">{{cite journal| author=Timson DJ| title=The structural and molecular biology of type III galactosemia. | journal=IUBMB Life | year= 2006 | volume= 58 | issue= 2 | pages= 83-9 | pmid=16611573 | doi=10.1080/15216540600644846 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=16611573  }} </ref> This is the mildest type.


===Galactosemia Type 2===
===Type IV===
 
*This type has only been discovered recently.  
Galactosemia type 2 is less common than classic galactosemia and is less harmful. It does not generally lead to hepatomegaly or brain damage. It is caused by the defect in both copies of the gene that codes for the enzyme galactokinase or GALK.
*Abnormal changes in the [[galactose mutatrose]] enzyme, encoded by the GALM [[gene]],  have been proven to cause the disorder. <ref name="pmid33181226">{{cite journal| author=Banford S, Timson DJ| title=The structural and molecular biology of type IV galactosemia. | journal=Biochimie | year= 2021 | volume= 183 | issue=  | pages= 13-17 | pmid=33181226 | doi=10.1016/j.biochi.2020.11.001 | pmc= | url=https://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=33181226  }} </ref>
 
===Galactosemia type 3===
 
Galactosemia type 3 is a very rare form of the disorder. There are two forms of Galactosemia type 3, a severe form and a benign form. This type of galactosemia is caused by defects in the gene that codes for the enzyme uridyldiphosphogalactose-4-epimerase or GALE.


==References==
==References==

Latest revision as of 09:13, 10 May 2022

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Dayana Davidis, M.D. [2]

Overview

Galactosemia consists of four types of disorders resulting from abnormal activity of the enzymes involved in galactose metabolism. Type I/ Classical is the most serious form of the disease.

Types

Galactosemia refers to a group of autosomal recessive disorders of galactose metabolism. They are classified into the following types based on the enzymatic activity [1]

Type I/Classical

  • Defects in both copies of the gene that codes for the enzyme galactose-1-phosphate uridyl transferase or GALT.[2].
  • Most common and severe form.
    • Duarte galactosemia
      • Variant of classic galactosemia.
      • Galactose metabolised to some extent as GALT not completely absent
      • Less severe symptoms than other forms

Type II

  • Defect in both copies of the gene that codes for the enzyme galactokinase or GALK.[3]
  • Less common and harmful than classic galactosemia.
  • Does not generally lead to hepatomegaly or brain damage.

Type III

  • Alterations in the gene coding for epimerase enzyme.[4] This is the mildest type.

Type IV

  • This type has only been discovered recently.
  • Abnormal changes in the galactose mutatrose enzyme, encoded by the GALM gene, have been proven to cause the disorder. [5]

References

  1. ↑ Banford S, McCorvie TJ, Pey AL, Timson DJ (2021). "Galactosemia: Towards Pharmacological Chaperones". J Pers Med. 11 (2). doi:10.3390/jpm11020106. PMC 7914515 Check |pmc= value (help). PMID 33562227 Check |pmid= value (help).
  2. ↑ Coelho AI, Rubio-Gozalbo ME, Vicente JB, Rivera I (2017). "Sweet and sour: an update on classic galactosemia". J Inherit Metab Dis. 40 (3): 325–342. doi:10.1007/s10545-017-0029-3. PMC 5391384. PMID 28281081.
  3. ↑ Holden HM, Thoden JB, Timson DJ, Reece RJ (2004). "Galactokinase: structure, function and role in type II galactosemia". Cell Mol Life Sci. 61 (19–20): 2471–84. doi:10.1007/s00018-004-4160-6. PMID 15526155.
  4. ↑ Timson DJ (2006). "The structural and molecular biology of type III galactosemia". IUBMB Life. 58 (2): 83–9. doi:10.1080/15216540600644846. PMID 16611573.
  5. ↑ Banford S, Timson DJ (2021). "The structural and molecular biology of type IV galactosemia". Biochimie. 183: 13–17. doi:10.1016/j.biochi.2020.11.001. PMID 33181226 Check |pmid= value (help).

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