PEDBASE.org - The Pediatric Database - Detailed information of GALACTOSEMIA-2

GALACTOSEMIA-II

DEFINITION:

A disorder of galactose metabolism characterized by a deficiency of galactokinase activity resulting in toxic injury to the eyes.

EPIDEMIOLOGY:

incidence: 1/40,000
age of onset:
- cataracts may begin forming in infancy
risk factors:
- familial - autosomal recessive
  - chrom.#: ?
  - gene: galactokinase
- M = F

PATHOGENESIS:

1. Background

galactokinase catalyzes the conversion of galactose to galactose- 1-phosphate
lactose (a milk carbohydrate) is a disaccharide of glucose and galactose

2. Genetic Defect

genetic defect -> deficiency of galactokinase activity -> accumulation of galactose -> some of which is converted into galactitol which may be responsible for cataract formation

CLINICAL FEATURES:

cataracts
normal intelligence

INVESTIGATIONS:

1. Urine

test for reducing substance after feeding human or cow's milk or formula containing lactose
positive for reducing substance (galactosuria)
- positive Clinitest but negative Clinistix indicates that the reducing substance is not glucose
- galactose identified by chromatography

2. Serum

galactosemia

3. Diagnosis

deficiency of galactokinase activity in RBC's
heterozygotes have intermediate activity

MANAGEMENT:

1. Diet

eliminate lactose and galactose from the diet
if initiated early enough, can reverse cataract formation

Pediatric Database - GALACTOSEMIA-2

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