Die Bedeutung des Mangels an Vitamin B12 (Cobalamin) wird vielfach unterschätzt. Vitamin-B12-Mangel lässt sich am zuverlässigsten durch Bestimmung von Methylmalonylsäure (MMA) bzw. Homozystein (HCY) im Plasma oder Serum erfassen. Mit der alleinigen Bestimmung von Vitamin B12 im Serum kann ein klinisch relevanter Vitamin-B12-Mangel nicht sicher diagnostiziert werden. Nach neueren, gründlichen Laboranalysen ist anzunehmen, dass 50 - 60 % der Senioren, die älter als 65 Jahre sind, Zeichen eines Vitamin-B12-Mangels aufweisen. Eine wesentliche Ursache dieser Problematik ist die atrophische Gastritis, die gerade im Alter häufig auftritt. Die klinische Bedeutung dieses Ergebnisses wird betont durch die Tatsache, dass Vitamin-B12-Mangel ein unabhängiger Risikofaktor für kardiovaskuläre Erkrankungen und thromboembolische Ereignisse darstellt und M. Alzheimer bzw. senile Demenz verursachen oder verschlimmern kann. Hämatologische Symptome (makrozytäre Anämie, Panzytopenie) treten nur bei etwa 1/3 der Menschen mit Vitamin-B12-Mangel auf. Die Notwendigkeit einer frühzeitigen Diagnostik wird verdeutlicht durch die Tatsache, dass gerade die neuropsychiatrischen Symptome nach Vitamin-B12-Substitution zunächst häufig reversibel sind. Die Substitution von Cobalamin kann parenteral (bei gastrointestinalen Begleiterkrankungen zu bevorzugen) oder oral erfolgen. Die applizierten Dosen (gerade im Fall oraler Substitution) und die Effektivität der Substitution sollten kontrolliert werden.
Abstract
The clinical relevance of vitamin B12 (cobalamin) deficiency is often underestimated. Vitamin B12 deficiency can be confirmed most reliably by the measurement of methylmalonic acid (MMA) and homocysteine (HCY) in plasma or serum. However, clinically relevant vitamin B12 deficiency cannot be confirmed merely by quantification of vitamin B12 in the serum. According to recent carefully performed laboratory studies 50 - 60 % of the elderly (> 65 years of age) have signs of vitamin B12 deficiency. A major cause of this observation is atrophic gastritis the prevalence of which is high in elderly people. The clinical relevance of such results is emphasized by the fact that vitamin B12 deficiency is an independent risk factor for cardiovascular diseases and thromboembolic events, and it can induce or aggravate neurological diseases such as Alzheimer disease or senile dementia. Haematological disorders (macrocytosis, anaemia, pancytopenia) occur in only ⅓ of persons with vitamin B12 deficiency. The necessity of an early diagnosis becomes clear by the fact that particularly the neurological symptoms arc reversible in many non-advanced cases. Both parenteral (in patients with gastrointestinal diseases preferred) and oral substitution of cobalamin is possible. The doses administered (particularly the oral doses) and the effectiveness of the substitution should be controlled.
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