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Pernicious Anemia; Causes, Symptoms, Diagnosis, Treatment

Pernicious anemia (also known as Biermer’s disease) is an autoimmune atrophic gastritis, predominantly of the fundus, and is responsible for a deficiency in vitamin B12 (cobalamin) due to its malabsorption. Its prevalence is 0.1% in the general population and 1.9% in subjects over the age of 60 years. Pernicious anemia represents 20%–50% of the causes of vitamin B12 deficiency in adults. Given its polymorphism and broad spectrum of clinical manifestations, pernicious anemia is a great pretender. Its diagnosis must therefore be evoked and considered in the presence of neurological and hematological manifestations of undetermined origin. Biologically, it is characterized by the presence of anti-intrinsic factor antibodies. Treatment is based on the administration of parenteral vitamin B12, although other routes of administration (eg, oral) are currently under study. In the present update, these various aspects are discussed with special emphasis on data of interest to the clinician.

Pernicious anemia is the loss of stomach cells that make intrinsic factor. Intrinsic factor helps the body absorb vitamin B12 in the intestine. The loss of parietal cells may be due to destruction by the body’s own immune system.

Pernicious anemia (PA) (also known as Biermer’s disease[Rx] and Addisonian anemia[Rx]) is a macrocytic anemia due to vitamin B₁₂ (cobalamin) deficiency, which, in turn, is the result of deficiency of intrinsic factor, a protein that binds avidly to dietary vitamin B₁₂ and promotes its transport to the terminal ileum for absorption[Rx]. The deficiency of intrinsic factor is a consequence of the presence of atrophic body gastritis (ABG), which results in the destruction of the oxyntic mucosa, and thus, the loss of parietal cells, which normally produce chlorhydric acid as well as intrinsic factor[Rx]. The term PA is sometimes used as synonym for cobalamin deficiency or for macrocytic anemia, but to avoid ambiguity, PA should be reserved for conditions that result from impaired secretion of intrinsic factor and atrophy of oxyntic mucosa[5]. However, differential diagnosis may sometimes be challenging due to the limit of available diagnostic tools.PA is considered an autoimmune disorder due to the frequent presence of gastric autoantibodies directed against intrinsic factor, as well as against parietal cells. PA is often considered a synonym of autoimmune gastritis, because PA is thought to be the end stage of an autoimmune process that results in severe damage of the oxyntic gastric mucosa[Rx].

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Causes of Pernicious Anemia

Autoimmune diseases, such as type 1 diabetes
Crohn’s disease
Having part or all of your stomach or intestine taken out
meat
poultry
shellfish
eggs
dairy products
fortified soy, nut, and rice milks
nutritional supplements
long-term use of certain medications and antibiotics, such as methotrexate and azathioprine
chronic obstructive pulmonary disease (COPD)
folate (vitamin B-9) deficiency caused by poor diet or conditions that affect absorption
chronic alcoholism
HIV
Cimetidine (used to treat peptic ulcers)
Omeprazole and Lansoprazole (proton pump inhibitors)
Phenobarbital, Pregabalin, Primidone and Topiramate (epilepsy)
Metformin (Type 2 Diabetes)
A strict vegetarian diet puts you at risk for PA too, since you won’t be eating foods that are rich in B-12 like eggs, milk, and poultry.
Pernicious anemia is a type of macrocytic anemia. It’s sometimes called megaloblastic anemia because of the abnormally large size of the red blood cells produced.

Pathologically, PA is characterized by at least the following elements:

The destruction of the gastric mucosa, especially fundic, by a process of cell-mediated autoimmunity.Rx,
A fundic atrophy accompanied by a reduction in gastric acid secretion, a reduction in intrinsic factor (IF) secretion, and vitamin B12 malabsorption, which is corrected by the addition of IF.1,Rx
The presence of various antibodies, including antibodies detectable in both plasma and gastric secretions in the form of anti-IF antibodies and antigastric parietal cell (anti-GPC) antibodies, the latter being specifically directed against the hydrogen potassium adenosine triphosphatase (H⁺/K⁺-ATPase) proton pump.Rx

Certain diseases can also raise your risk. They include

Addison disease
Chronic thyroiditis
Graves disease
Hypoparathyroidism
Hypopituitarism
Myasthenia gravis
Secondary amenorrhea
Type 1 diabetes
Testicular dysfunction
Vitiligo

Symptoms of Pernicious Anemia

PA affects people in different ways. These can be signs you have it

Fatigue (Many people wake up tired despite getting enough sleep.)
Shortness of breath
Feeling dizzy
Cold hands and feet
Chest pain
Pale or yellow skin
Trouble with balance (for example, struggling to put on your pants or socks while you’re standing)
A burning feeling in your legs or feet. This may get worse at night
Depression
Trouble focusing
Weight loss
An unsteady gait
Spasticity, which is stiffness and tightness in the muscles
Peripheral neuropathy, which is numbness in the arms and legs
Progressive lesions of the spinal cord
Memory loss
Nausea and vomiting
Confusion
Constipation
Loss of appetite
Heartburn

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Diagnosis of Pernicious Anemia

A complete blood cell count (CBC)
Examination of a blood smear (peripheral smear) under a microscope, often performed in association with a CBC
Blood vitamin B-12 level measurements
Tests for the presence of autoantibodies to intrinsic factor or stomach lining cells
Blood levels of iron and iron-binding capacity
Folate levels (which are often reduced when vitamin B-12 levels are low)
Blood levels of methylmalonic acid or homocysteine, both of which may be sensitive indicators of vitamin B-12 deficiency
The Schilling test, a measure of how well the body can absorb vitamin B-12, is less commonly used today than in the past.
Finally, bone marrow aspiration or bone marrow biopsy may be recommended in some cases if bone marrow disorders are suspected
Tests to measure blood levels of methylmalonic acid (MMA) or homocysteine, both of which may be sensitive indicators of vitamin B-12 deficiency;
An elevated MMA level is seen with B-12 deficiency, whereas elevated homocysteine levels are characteristic of both B-12 and folate deficiencies;
Bone marrow aspiration or bone marrow biopsy may be recommended in some cases to examine for the presence of bone marrow disorders.
Reticulocyte count, which measures how fast premature red blood cells, called reticulocytes, are made by bone marrow and released into blood

Main clinical manifestations of vitamin B12 deficiency

Neuropsychiatric manifestations	Digestive manifestations	Other manifestations
Frequent	Frequent	Vaginal mucosa atrophy
Combined sclerosis of the spinal cord	Hunter’s glossitis	Urogenital infections (especially mycoses)
Polyneuritis	Hemolytic icterus	Rebellious or recurrent cutaneous–mucosal ulcers
Ataxias	Others	Thrombosis (venous thromboembolism and ischemic heart disease)
Babinski	Abdominal pain	Subfertility and recurrent spontaneous abortions/male infertility
Rare	GI transit disorders
Cerebellar syndrome
Cranial nerve impairment
Sphincter dysfunctions
Others
Memory impairments
Dementia
Atherosclerosis
Parkinsonism
Depression

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Abbreviation: GI, gastrointestinal.

Treatment of Pernicious Anemia

The treatment of PA varies by country and area. Opinions vary over the efficacy of administration (parenteral/oral), the amount and time interval of the doses, or the forms of vitamin B₁₂ (e.g. cyanocobalamin/hydroxocobalamin). More comprehensive studies are still needed in order to validate the feasibility of a particular therapeutic method for PA in clinical practices. A permanent cure for PA is lacking, although repletion of B₁₂ should be expected to result in cessation of anemia-related symptoms, a halt in neurological deterioration, and in cases where neurological problems are not advanced, neurological recovery and a complete and permanent remission of all symptoms, so long as B₁₂ is supplemented. Repletion of B₁₂ can be accomplished in a variety of ways.

Intramuscular injections

The standard treatment for PA has been intramuscular injections of cobalamin in the form of cyanocobalamin (CN-Cbl), hydroxocobalamin (OH-Cbl) or methylcobalamin.