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Mild transcobalamin I (haptocorrin) deficiency and low serum cobalamin concentrations.

Abstract

BACKGROUND

Low cobalamin concentrations are common, but their causes are often unknown. Transcobalamin I/haptocorrin (TC I/HC) deficiency, viewed as a rare cause, has not been examined systematically in patients with unexplained low serum cobalamin.

METHODS

Total TC I/HC was measured by RIA in three subgroups of 367, 160, and 38 patients with different categories of low cobalamin concentrations and three comparison subgroups of 112, 281, and 119 individuals with cobalamin concentrations within the reference interval. Additional studies, including family studies, were done in selected patients found to have low TC I/HC concentrations.

RESULTS

Low TC I/HC concentrations suggestive of mild TC I/HC deficiency occurred in 54 of 367 (15%) patients with low cobalamin identified by clinical laboratories and 24 of 160 (15%) patients whose low cobalamin was unexplained after absorption and metabolic evaluation, but in only 2 of 38 patients with malabsorptive causes of low cobalamin concentrations (5%). The prevalence was only 3% (8 of 281 plasma samples) to 5% (6 of 112 sera) in patients with cobalamin concentrations within the reference interval and 3% (4 of 119) in healthy volunteers. Three patients with low cobalamin (0.6%) had severe TC I/HC deficiency with undetectable TC I/HC. Presumptive heterozygotes for severe TC I/HC deficiency in two families had the findings of mild TC I/HC deficiency; mild deficiency was also found in at least three of seven studied families of patients with mild TC I/HC deficiency.

CONCLUSIONS

Mild TC I/HC deficiency is frequently associated with low cobalamin, is often familial, and its biochemical phenotype appears identical to the heterozygous state of severe TC I/HC deficiency. Severe TC I/HC deficiency also appears to be more common than suspected. Both diagnoses should be considered in all patients with unexplained low serum cobalamin.

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  • Authors+Show Affiliations

    Department of Medicine, New York Methodist Hospital, 506 Sixth Street, Brooklyn, NY 11215, USA. rac9001@nyp.org

    Source

    Clinical chemistry 49:8 2003 Aug pg 1367-74

    MeSH

    Adult
    Aged
    Data Collection
    Family
    Female
    Heterozygote
    Humans
    Male
    Middle Aged
    Reference Values
    Transcobalamins
    Vitamin B 12

    Pub Type(s)

    Journal Article
    Research Support, U.S. Gov't, P.H.S.

    Language

    eng

    PubMed ID

    12881454

    Citation

    Carmel, Ralph. "Mild Transcobalamin I (haptocorrin) Deficiency and Low Serum Cobalamin Concentrations." Clinical Chemistry, vol. 49, no. 8, 2003, pp. 1367-74.
    Carmel R. Mild transcobalamin I (haptocorrin) deficiency and low serum cobalamin concentrations. Clin Chem. 2003;49(8):1367-74.
    Carmel, R. (2003). Mild transcobalamin I (haptocorrin) deficiency and low serum cobalamin concentrations. Clinical Chemistry, 49(8), pp. 1367-74.
    Carmel R. Mild Transcobalamin I (haptocorrin) Deficiency and Low Serum Cobalamin Concentrations. Clin Chem. 2003;49(8):1367-74. PubMed PMID: 12881454.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Mild transcobalamin I (haptocorrin) deficiency and low serum cobalamin concentrations. A1 - Carmel,Ralph, PY - 2003/7/26/pubmed PY - 2003/8/21/medline PY - 2003/7/26/entrez SP - 1367 EP - 74 JF - Clinical chemistry JO - Clin. Chem. VL - 49 IS - 8 N2 - BACKGROUND: Low cobalamin concentrations are common, but their causes are often unknown. Transcobalamin I/haptocorrin (TC I/HC) deficiency, viewed as a rare cause, has not been examined systematically in patients with unexplained low serum cobalamin. METHODS: Total TC I/HC was measured by RIA in three subgroups of 367, 160, and 38 patients with different categories of low cobalamin concentrations and three comparison subgroups of 112, 281, and 119 individuals with cobalamin concentrations within the reference interval. Additional studies, including family studies, were done in selected patients found to have low TC I/HC concentrations. RESULTS: Low TC I/HC concentrations suggestive of mild TC I/HC deficiency occurred in 54 of 367 (15%) patients with low cobalamin identified by clinical laboratories and 24 of 160 (15%) patients whose low cobalamin was unexplained after absorption and metabolic evaluation, but in only 2 of 38 patients with malabsorptive causes of low cobalamin concentrations (5%). The prevalence was only 3% (8 of 281 plasma samples) to 5% (6 of 112 sera) in patients with cobalamin concentrations within the reference interval and 3% (4 of 119) in healthy volunteers. Three patients with low cobalamin (0.6%) had severe TC I/HC deficiency with undetectable TC I/HC. Presumptive heterozygotes for severe TC I/HC deficiency in two families had the findings of mild TC I/HC deficiency; mild deficiency was also found in at least three of seven studied families of patients with mild TC I/HC deficiency. CONCLUSIONS: Mild TC I/HC deficiency is frequently associated with low cobalamin, is often familial, and its biochemical phenotype appears identical to the heterozygous state of severe TC I/HC deficiency. Severe TC I/HC deficiency also appears to be more common than suspected. Both diagnoses should be considered in all patients with unexplained low serum cobalamin. SN - 0009-9147 UR - https://www.unboundmedicine.com/medline/citation/12881454/full_citation L2 - http://www.clinchem.org/cgi/pmidlookup?view=long&pmid=12881454 DB - PRIME DP - Unbound Medicine ER -