PubMed · 6836536
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B L Therrell, L O Brown, P E Dziuk, W P Peter. 1983. The Texas Newborn Screening Program.. https://pubmed.ncbi.nlm.nih.gov/6836536/
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Classical galactosaemia (Mendelian Inheritance in Man, no 230400) is an autosomal recessive disorder of galactose metabolism caused by a deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT). The GALT enzyme is responsible for the conversion of galactose-1-phosphate with UDP glucose to glucose-1-phosphate and UDP galactose. The gene encoding for GALT is located on chromosome 9p13. Patients present with hepatomegaly, liver failure, food intolerance, hypoglycaemia, muscle hypotonia, sepsis and cataract. Treatment involving the total restriction of lactose-containing foods is life-saving but many patients develop late complications such as problems of mental development, disorders of motor function, disorders of speech and hypergonadotrophic hypogonadism.
Classic galactosemia is due to the deficiency of galactose-1-phosphate uridyl transferase and is transmitted as an autosomal recessive disorder. Patients suffering from classic galactosemia display acute symptoms such as poor growth, feeding difficulties, jaundice, hepatomegaly etc., which disappear when the individual is on galactose free diet. However, these patients continue to suffer from defects such as neurological disturbances and ovarian dysfunction, due to the accumulation of galactose-1-phosphate, which is a normal intermediate of galactose metabolism. The biochemical mechanism of galactose-1-phosphate mediated toxicity is still an enigma. Recent experiments strongly suggest that galactose-1-phosphate is also a substrate for inositol monophosphatase (IMPase). Phosphatidylinositol bisphosphate [PI(P)2] dependent signaling serves as a second messenger for several neurotransmitters in the brain. Therefore, the brain is critically dependent on IMPase for the supply of free inositol in order to sustain [PI(P)2] signaling. Circumstantial evidence strongly supports the possibility that being a substrate, galactose-1-phosphate could modulate IMPase function in vivo. The implication of this idea is discussed in relation to classic galactosemia as well as bipolar disorder, which has been thought to be due to the hyper-activation of [PI(P)2] mediated second messenger pathways(s).
UNLABELLED: Glucose-6-phosphate dehydrogenase (G6PD) deficiency is an X-linked recessive disorder in which haemolytic anaemia is the major symptom. The Beutler spot test employed in mass-screening for galactosaemia in newborns requires several intrinsic erythrocyte enzymes such as G6PD for its reaction and can theoretically detect G6PD deficiency apart from galactose-1-phosphate uridyltransferase deficiency. In this study, we detected two patients with G6PD deficiency using the quantitative Beutler test which was recently developed in our laboratory. Both patients lacked erythrocyte G6PD activity but exhibited no clinical symptoms. Molecular analysis in patients 1 and 2 revealed two novel missense mutations of C853T causing R285C and A1220C causing K407T, respectively. Molecular rather than enzymatic analysis was required in familial studies to detect and diagnose the carrier state. To date these patients have avoided oxidant stress and haemolytic diatheses have not been induced. CONCLUSION: Our results indicate that the quantitative Beutler test can detect glucose-6-phosphate dehydrogenase deficiency of class 1 and 2 and is therefore useful for early intervention and prevention of haemolytic diathesis in patients with this disorder.