Laboratory Studies
Clinitest
Most hospitals use Clinitest in the diagnosis of galactokinase deficiency, the simplest laboratory test available to detect reducing sugars (eg, glucose, lactose, or fructose, which reduce copper salts in Clinitest tablets) in the urine.
Always correlate a positive Clinitest result with a test specific for glucose, such as Clinistix. Alternatively, galactose may be identified directly with paper or gas chromatography. If galactose is found, galactose-1-phosphate concentration should also be measured to conclusively exclude transferase-deficient galactosemia.
Definitive biochemical diagnosis is based on assessment of red cell galactokinase activity.
Imaging Studies
No imaging studies are required.
Other Tests
Once a definitive diagnosis is established, no further testing is needed.
Procedures
No diagnostic procedures are required.
Histologic Findings
No histologic findings are associated with galactokinase deficiency. Cataracts bear no distinguishing features that identify their etiology.
-
UDP-galactose synthesis and galactosemia. The most common form of galactosemia is due to a deficiency of galactose-1-phosphate uridyltransferase (GALT). This enzyme normally uses galactose-1-phosphate derived from dietary galactose. In the absence of GALT, galactose-1-phosphate accumulates, along with excessive galactose and its oxidative and reductive products galactitol and galactonate (not shown). UDP-galactose synthesis may also be impaired in the absence of GALT but not completely because UDP-galactose-4′-epimerase (GALE) can form UDP-galactose from UDP-glucose and can supply the donor to galactosyltransferases required for normal glycoconjugate biosynthesis.
