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Síndrome demencial secundário a malabsorção de vitamina B12 : relato de um caso clínico
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A diversidade de etiologias e as múltiplas formas de apresentação clínica podem tornar o diagnóstico de demência num desafio. É conhecida a associação entre esta e perturbações no metabolismo da vitamina B12. Apresenta-se o caso de uma mulher caucasiana de 58 anos com diagnóstico prévio, mas não confirmado, de anemia perniciosa, sob reposição irregular de vitamina B12, que foi internada por défice cognitivo, desequilíbrio na marcha e parestesias nos membros inferiores de agravamento progressivo com 1 ano de evolução, a que se associou síndrome consumptiva com 3 meses de evolução. Em internamento não se verificou a anemia nem a presença de anticorpos anti-células parietais e foi excluída infeção ou neoplasia do sistema nervoso central ou outro. O estudo eletrofisiológico era compatível com polineuropatia sensitivo-motora desmielinizante a nível periférico. A ressonância magnética crânio-encefálica e medular revelou atrofia frontal e bitemporal, sem lesões desmielinizantes, vasculares ou ocupantes de espaço. Apesar da toma de vitamina B12 e de os níveis séricos da mesma se situarem dentro dos valores de referência, foi demonstrada uma reposição insuficiente através do doseamento de nível elevado de ácido metilmalónico. Trata-se então de um caso de demência precoce secundária a perturbação no metabolismo de B12 por défice de reposição, apesar de ter níveis séricos normalizados.
The diversity in clinical presentations and etiologies can turn the diagnosis of dementia into a challenge. There is a known link between dementia and dysfunctions of vitamin B12 metabolism. The author presents the case of a 58 year old caucasian woman with a previous, but unconfirmed, diagnosis of pernicious anaemia, under irregular vitamin B12 supplementation, admitted to the hospital with complaints of cognitive deficit, ataxia and paresthesia of the lower limbs which had been progressing for 1 year prior to admission, associated with a consumptive syndrome which started 3 months before admission. Workup performed during her stay showed no evidence of anaemia or anti-parietal cell antibodies; infection and cancer of the central nervous system or others were also excluded. The results of the electrophysiologic study were compatible with a peripheral nerve demyelinating motor-sensitive polyneuropathy. Magnetic resonance imaging of the central nervous system revealed frontal and bitemporal atrophy, with no evidence of demyelinating, vascular or space-occupying lesions. In spite of B12 intake and serum levels within normal reference values, insufficient reposition was demonstrated by measurement of high levels of methylmalonic acid. Thus, this is a case of dementia caused by vitamin B12 deficiency, which progressed in spite of normal serum levels of this vitamin.
The diversity in clinical presentations and etiologies can turn the diagnosis of dementia into a challenge. There is a known link between dementia and dysfunctions of vitamin B12 metabolism. The author presents the case of a 58 year old caucasian woman with a previous, but unconfirmed, diagnosis of pernicious anaemia, under irregular vitamin B12 supplementation, admitted to the hospital with complaints of cognitive deficit, ataxia and paresthesia of the lower limbs which had been progressing for 1 year prior to admission, associated with a consumptive syndrome which started 3 months before admission. Workup performed during her stay showed no evidence of anaemia or anti-parietal cell antibodies; infection and cancer of the central nervous system or others were also excluded. The results of the electrophysiologic study were compatible with a peripheral nerve demyelinating motor-sensitive polyneuropathy. Magnetic resonance imaging of the central nervous system revealed frontal and bitemporal atrophy, with no evidence of demyelinating, vascular or space-occupying lesions. In spite of B12 intake and serum levels within normal reference values, insufficient reposition was demonstrated by measurement of high levels of methylmalonic acid. Thus, this is a case of dementia caused by vitamin B12 deficiency, which progressed in spite of normal serum levels of this vitamin.
Descrição
Trabalho Final do Curso de Mestrado Integrado em Medicina, Faculdade de Medicina, Universidade de Lisboa, 2016
Palavras-chave
Demência Vitamina B 12 Deficiência de Vitamina B 12