Haptocorrin (Transcobalamin I) and Cobalamin Deficiencies

Carmel, Ralph

doi:10.1373/clinchem.2006.078808

Cited by 4 publications

(2 citation statements)

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“…TC I and cobalamin levels correlate strongly in normal plasma (Carmel et al , 2001; Morkbak et al , 2006) because the same holo‐TC I accounts for >70% of both those levels (Carmel, 2007). In severe TC I deficiency, however, plasma cobalamin is attached only to TC II (holo‐TC II) and some minor, unidentified binding proteins mentioned earlier.…”

Section: Discussionmentioning

confidence: 99%

“…It has been associated with severely impaired granulopoiesis (Carmel et al , 1975; Carmel, 1981, 1983b). However, proposed acquired TC I deficiency in patients with acquired immunodeficiency syndrome (AIDS) and pregnant women with often low cobalamin levels appears to be limited to holo‐TC I reduction (Hansen et al , 1992; Koebnick et al , 2002), and a proposal that cobalamin deficiency itself reduces total TC I (Morkbak et al , 2006) has raised methodological concerns (Carmel, 2007).…”

Section: Discussionmentioning

confidence: 99%

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Genomic mutations associated with mild and severe deficiencies of transcobalamin I (haptocorrin) that cause mildly and severely low serum cobalamin levels

2009

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Summary Transcobalamin (TC) I deficiency, like the function of TC I itself, is incompletely understood. It produces low serum cobalamin levels indistinguishable from those of true cobalamin deficiency. Diagnosis is especially elusive when TC I deficiency is mild. To provide new, more substantive definition, the TCN1 gene was examined in two well‐characterised families that included members with both severe and mild TC I deficiencies. A severely deficient proposita with undetectable TC I levels displayed compound heterozygosity for two mutations, each causing a premature stop codon. Relatives in both families who had mildly low or low‐normal plasma levels of TC I and cobalamin were heterozygous for one or the other of these mutations. An unrelated patient with mild TC I deficiency and unknown familial TC I and cobalamin status was then tested and found to be similarly heterozygous for one of the mutations. The two nonprivate mutations identify a genetic basis for TC I deficiency for the first time. They also add new approaches to studying mild and severe TC I deficiency and to reducing confusion of its low cobalamin levels with those of cobalamin deficiency and its often dramatically different prognosis and management.

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Section: Discussionmentioning

confidence: 99%