Thiamine deficiency- Beriberi

Pathogenesis: Thiamine (vitamin B1) is a water-soluble vitamin present in most animal and plant tissues. Neuropathy due to thiamine deficiency, known as beriberi, was the first clinically described deficiency syndrome in humans. Beriberi may manifest with heart failure (wet beriberi) or without heart failure (dry beriberi). Thiamine deficiency is also responsible for Wernicke’s encephalopathy and Korsakoff’s syndrome. Thiamine diphosphate (TDP) serves as an essential co-factor in cellular respiration, ATP production, synthesis of glutamate and γ-aminobutyric acid and myelin sheath maintenance.

Clinical Features: Symptoms usually develop gradually over weeks to months, but sometimes they may manifest rapidly over a few days. Clinical features of thiamine deficiency begin with distal sensory loss, burning pain,  muscle weakness in the toes and feet. There is often associated aching and cramping in the lower legs. Left untreated, the neuropathy will cause ascending weakness in the legs and eventually evolve to a sensorimotor neuropathy in the hands.Approximately 25% of patients with thiamine deficient polyneuropathy may also have Wernicke’s encephalopathy which manifests as ophthalmoplegia (paralysis of ocular muscle), ataxia (abnormal gait, inability to stand), nystagmus (involuntary, uncontrollable eye movements) and encephalopathy

Treatment: When a diagnosis of thiamine deficiency is made or suspected, thiamine replacement should be provided until proper nutrition is restored. Thiamine is usually given intravenously or intramuscularly at an initial dose of 100 mg followed by 100 mg per day.

Vitamin B12 Deficiency

Pathogenesis: Vitamin B12 (cobalamin) is present in animal and dairy products and is synthesized by specific microorganisms. Humans depend on nutritional intake for their vitamin B12 supply. Vitamin B12 deficiency has been observed in 5% to 20% of older adults and up to 40% of older adults have low serum vitamin B12 levels. Cases of vitamin B12 deficiency can be due to malabsorption, pernicious anemia, gastrointestinal surgeries and weight reduction surgery. As vitamin B12 is only found in animal products strict vegan diets lack vitamin B12 and must be supplemented. Certain medications may contribute to vitamin B12 deficiency namely proton pump inhibitors and metformin.

Clinical Features: Vitamin B12 (cobalamin) deficiency is associated with hematologic, neurologic, and psychiatric manifestations. Subacute combined degeneration, neuropsychiatric symptoms, peripheral neuropathy and optic neuropathy are the classic neurological consequences of B12 deficiency. Patients may present with neurological symptoms regardless of a normal hematological picture. The neuropathy associated with B12 deficiency usually begins with sensory symptoms in the feet.

Treatment: Early diagnosis is critical since patients with advanced disease may be left with major residual disability. Common treatment regimen includes administration of 1000 mcg intramuscularly daily for 5–7 days, followed by 1000 mcg IM monthly. Other approaches are a once-a-week injections for four weeks, and then monthly injections