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Transferase-Deficiency Galactosemia and the Duarte Variant-Reply

Frank K. Thorp, MD, PhD
JAMA. 1987;257(2):188. doi:10.1001/jama.1987.03390020053017.
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In Reply.—  I appreciate the comments of Dr Ng and colleagues regarding the issue of diet therapy for a child who is a mixed heterozygote for transferase-deficiency galactosemia and the Duarte variant, and apologize for the incorrect and confusing statement in my abbreviated answer regarding the anticipated enzyme level. Beutler's studies' on the distribution of transferase enzyme activity in parents and children from families with the galactosemia gene (gt) and the Duarte gene (GtD) indicate the following, expressed as percent of normal (Gt+) enzyme activity: Gt+/Gt+ = 100%; Gt+/gt = 50%; gt/gt = 0%; Gt+/GtD = 75%; GtD/GtD = 50%; and GtD/gt = 25%.1The actual levels of transferase enzyme activity, measured in red blood cells or other tissues, in any given subject, may deviate somewhat from these mean values, and will therefore result in a range of metabolic and clinical manifestations in different individuals


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