<unk>  often presents slowly, and can cause harm insidiously and unnoticeably. Untreated, it can lead to neurological complications, and in serious cases, death. It can take several years for<unk>  to appear, and the disease often goes unrecognized, as the body becomes used to feeling unwell. The onset may be vague and slow, as the same symptoms are often also present with<unk> ; in 20% of cases of cobalamin deficiency,<unk>  is not observed.<unk>  may present with a wide range of signs and symptoms, such as feeling tired and weak, lightheadedness, dizziness, headaches, rapid heartbeat, irregular heartbeat, breathlessness, glossitis (a sore red tongue), a frequent drop in blood pressure, cold hands and feet,<unk> le skin, easy bruising and bleeding, low-grade fevers, shakiness and cold sensitivity, chest<unk> in, upset stomach, nausea, angular cheilitis, loss of appetite, heartburn, weight loss, diarrhea, constipation, severe joint<unk> in, feeling abnormal sensations including tingling or numbness to the fingers and toes (pins and needles), and tinnitus.<unk>  may present with a number of further common symptoms, including hair thinning and loss, early greying of the hair, mouth ulcers, bleeding gums, a yellowish skin (jaundice), a look of exhaustion with<unk> le and dehydrated or cracked lips and dark circles around the eyes, as well as brittle nails. In more severe or prolonged cases of<unk> , nerve cell damage may occur, which can lead to a more severe symptoms, including sense loss, difficulty in proprioception, neuropathic<unk> in, unsteady walking (ataxia), poor balance, loss of sensation in the feet, muscle weakness, blurred vision (either due to retinopathy or optic neuropathy), impaired urination, fertility problems, decreased level of consciousness, changes in reflexes, memory loss, mood swings, depression, irritability, cognitive impairment, confusion, anxiety, clumsiness, psychosis, and, in more severe cases, dementia. Decreased sense of taste or smell also may occur.<unk>  may also lead to cardiac murmurs and/or altered blood pressure (low or high). The deficiency may also present with thyroid disorders. In severe cases, the<unk>  may cause congestive heart failure. A complication of severe chronic<unk>  is subacute combined degeneration of spinal cord, which leads to distal sensory loss (posterior column), absent ankle reflex, increased knee reflex response, and extensor plantar response. Other than<unk> , hematological symptoms may include cytopenias, intramedullary hemolysis, and pseudothrombotic microangiopathy. Vitamin B12 deficiency, which is reversible, is occasionally confused with acute myeloid leukemia, which is an irreversible autoimmune condition presenting with some of the same hematological symptoms, including hypercellular bone marrow with blastic differentiation and hypersegmented neutrophils.<unk>  can contribute to a delay in physical growth in children, and may also be a cause for delay in puberty for adolescents.
Pernicious anemia
Zinc deficiency
Iron poisoning
Zinc toxicity
Hookworm infection
Fruit allergy
Pinworm infection
African iron overload