The Many Faces of Cobalamin (Vitamin B12) Deficiency

Abstract

Although cobalamin (vitamin B 12 ) deficiency was described over a century ago, it is still difficult to establish the correct diagnosis and prescribe the right treatment. Symptoms related to vitamin B 12 deficiency may be diverse and vary from neurologic to psychiatric. A number of individuals with vitamin B 12 deficiency may present with the classic megaloblastic anemia. In clinical practice, many cases of vitamin B 12 deficiency are overlooked or sometimes even misdiagnosed. In this review, we describe the heterogeneous disease spectrum of patients with vitamin B 12 deficiency in whom the diagnosis was either based on low serum B 12 levels, elevated biomarkers like methylmalonic acid and/or homocysteine, or the improvement of clinical symptoms after the institution of parenteral vitamin B 12 therapy. We discuss the possible clinical signs and symptoms of patients with B 12 deficiency and the various pitfalls of diagnosis and treatment.

Vitamin B12 Deficiency Anemia and Polyneuropathy Due to Chronic Radiation Enteritis

“…A significant vitamin B12 deficiency was reported in 20% of 55 patients at 6-12 years after pelvic radiation (11). Various causes of vitamin B12 deficiency have been recognized, but disease or resection of the ileum as the cause of absorption disturbance has been described in recent reviews (12)(13)(14). To our knowledge, no other reports have described a case of vitamin B12 deficiency associated with chronic radiation enteritis in Japan, and chronic radiation enteritis does not seem to be well recognized as a potential cause of vitamin B12 deficiency.…”

Pernicious anaemia can be treated effectively with a single high dose of cobalamin

“…Despite a concurrent increase in MMA and a drop in B12, we were unable to observe alterations in the CBC. This may be explained by previous observations showing that isolated abnormalities of B12 or MMA levels do not predict clinical or haematologic manifestations of a B12 deficiency 13,14 . No adverse events were observed.…”

Astrogliosis in an Experimental Model of Hypovitaminosis B12: A Cellular Basis of Neurological Disorders due to Cobalamin Deficiency

“…Cobalamin deficiency affects human physiology with sequelae ranging from mild fatigue to severe neuropsychiatric abnormalities. There have been many cases reported where nervous system disorders were the main presenting symptom, often leading to permanent disability [ 3 ]. However, the cellular and molecular aspects of the neurological disorders caused by hypovitaminosis B12 remain largely unknown.…”

“…The main complications of B12 deficiency are megaloblastic anaemia and neurological manifestations, such as sensory and motor disturbances, ataxia, cognitive decline leading to dementia and psychiatric disorders including mood and behaviour changes or psychosis. Despite the widespread belief that vitamin B12 deficiency is primarily associated with ineffective erythropoiesis, serious neurological complications often predominate and can frequently occur in the absence of anaemia [ 1 , 2 , 3 ]. The cellular and molecular mechanisms of the nervous system disorders associated with vitamin B12 deficiency remain largely unknown.…”