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Deficiency of galactokinase(GALAC2)

MedGen UID:
120614
Concept ID:
C0268155
Disease or Syndrome
Synonyms: Galactokinase Deficiency; Galactokinase deficiency with cataracts; Galactosemia 2; GALACTOSEMIA II; Hereditary galactokinase deficiency
SNOMED CT: Deficiency of galactokinase (124302001); Galactokinase deficiency galactosemia (124302001); Galactosemia II (124302001); Galactokinase deficiency (124302001); Galactosemia - galactokinase deficiency (124302001); GALK (galactokinase) deficiency (124302001)
Modes of inheritance:
Autosomal recessive inheritance
MedGen UID:
141025
Concept ID:
C0441748
Intellectual Product
Source: Orphanet
A mode of inheritance that is observed for traits related to a gene encoded on one of the autosomes (i.e., the human chromosomes 1-22) in which a trait manifests in individuals with two pathogenic alleles, either homozygotes (two copies of the same mutant allele) or compound heterozygotes (whereby each copy of a gene has a distinct mutant allele).
 
Gene (location): GALK1 (17q25.1)
 
Monarch Initiative: MONDO:0009255
OMIM®: 230200
Orphanet: ORPHA79237

Definition

Galactosemia II (GALAC2), or galactokinase deficiency, is an autosomal recessive disorder that causes cataract formation in children not maintained on a lactose-free diet. Cataract formation is the result of osmotic phenomena caused by the accumulation of galactitol in the lens (Asada et al., 1999). For a discussion of genetic heterogeneity of galactosemia, see GALAC1 (230400). [from OMIM]

Additional description

From MedlinePlus Genetics
Galactosemia type II (also called galactokinase deficiency) and type III (also called galactose epimerase deficiency) cause different patterns of signs and symptoms. Galactosemia type II causes fewer medical problems than the classic type. Affected infants develop cataracts but otherwise experience few long-term complications. The signs and symptoms of galactosemia type III vary from mild to severe and can include cataracts, delayed growth and development, intellectual disability, liver disease, and kidney problems.

Galactosemia is a disorder that affects how the body processes a simple sugar called galactose. A small amount of galactose is present in many foods. It is primarily part of a larger sugar called lactose, which is found in all dairy products and many baby formulas. The signs and symptoms of galactosemia result from an inability to use galactose to produce energy.

Researchers have identified several types of galactosemia. These conditions are each caused by mutations in a particular gene and affect different enzymes involved in breaking down galactose.

Classic galactosemia, also known as type I, is the most common and most severe form of the condition. If infants with classic galactosemia are not treated promptly with a low-galactose diet, life-threatening complications appear within a few days after birth. Affected infants typically develop feeding difficulties, a lack of energy (lethargy), a failure to gain weight and grow as expected (failure to thrive), yellowing of the skin and whites of the eyes (jaundice), liver damage, and abnormal bleeding. Other serious complications of this condition can include overwhelming bacterial infections (sepsis) and shock. Affected children are also at increased risk of delayed development, clouding of the lens of the eye (cataract), speech difficulties, and intellectual disability. Females with classic galactosemia may develop reproductive problems caused by an early loss of function of the ovaries (premature ovarian insufficiency).  https://medlineplus.gov/genetics/condition/galactosemia

Clinical features

From HPO
Galactosuria
MedGen UID:
120615
Concept ID:
C0268157
Disease or Syndrome
Elevated concentration of galactose in the urine.
Prolonged neonatal jaundice
MedGen UID:
347108
Concept ID:
C1859236
Finding
Neonatal jaundice refers to a yellowing of the skin and other tissues of a newborn infant as a result of increased concentrations of bilirubin in the blood. Neonatal jaundice affects over half of all newborns to some extent in the first week of life. Prolonged neonatal jaundice is said to be present if the jaundice persists for longer than 14 days in term infants and 21 days in preterm infants.
Increased intracranial pressure
MedGen UID:
56241
Concept ID:
C0151740
Finding
An increase of the pressure inside the cranium (skull) and thereby in the brain tissue and cerebrospinal fluid.
Hypergalactosemia
MedGen UID:
892325
Concept ID:
C4023071
Finding
Elevated concentration of galactose in the blood.
Cataract
MedGen UID:
39462
Concept ID:
C0086543
Disease or Syndrome
A cataract is an opacity or clouding that develops in the crystalline lens of the eye or in its capsule.

Term Hierarchy

CClinical test,  RResearch test,  OOMIM,  GGeneReviews,  VClinVar  
Follow this link to review classifications for Deficiency of galactokinase in Orphanet.

Recent clinical studies

Prognosis

P S, Ebrahimi EA, Ghazala SA, D TK, R S, Priya Doss C G, Zayed H
J Cell Biochem 2018 Sep;119(9):7585-7598. Epub 2018 Jun 12 doi: 10.1002/jcb.27097. PMID: 29893426

Clinical prediction guides

P S, Ebrahimi EA, Ghazala SA, D TK, R S, Priya Doss C G, Zayed H
J Cell Biochem 2018 Sep;119(9):7585-7598. Epub 2018 Jun 12 doi: 10.1002/jcb.27097. PMID: 29893426

Supplemental Content

Table of contents

    Clinical resources

    Practice guidelines

    • PubMed
      See practice and clinical guidelines in PubMed. The search results may include broader topics and may not capture all published guidelines. See the FAQ for details.
    • Bookshelf
      See practice and clinical guidelines in NCBI Bookshelf. The search results may include broader topics and may not capture all published guidelines. See the FAQ for details.

    Curated

    • ACMG Algorithm, 2022
      American College of Medical Genetics Algorithm, Primary or Secondary Hypergalactosemia (Galactose Elevated)
    • ACMG ACT, 2022
      American College of Medical Genetics and Genomics, Newborn Screening ACT Sheet, Elevated total galactose with normal GALT enzyme activity, Primary or Secondary Hypergalactosemia, 2022
    • ACMG ACT, 2022
      American College of Medical Genetics ACT Sheet, Newborn Screening ACT Sheet Primary or Secondary Hypergalactosemia
    • ACMG ACT Sheet, 2010
      American College of Medical Genetics ACT SHEETs, Primary or Secondary Hypergalactosemia, 2010
    • ACMG Algorithm, 2009
      American College of Medical Genetics Algorithm, Primary or Secondary Hypergalactosemia, 2009

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