Pernicious anemia is a specific type of vitamin B12 deficiency resulting from the body’s inability to absorb this nutrient properly. It is considered an autoimmune disorder where the immune system mistakenly attacks cells in the stomach lining or a protein called intrinsic factor. Intrinsic factor is produced in the stomach and is necessary for vitamin B12 to be absorbed in the small intestine. Without adequate absorption of vitamin B12, the body cannot produce enough healthy red blood cells, which are responsible for carrying oxygen throughout the body. This deficiency can gradually lead to various health issues impacting multiple bodily systems.
Common Symptoms
Pernicious anemia often causes symptoms that develop gradually. A persistent feeling of fatigue and general weakness is often an early indicator. This pervasive tiredness can significantly impact daily activities and does not typically improve with rest.
Shortness of breath, especially during exertion, is common due to reduced oxygen-carrying capacity. Loss of appetite and unintended weight loss can also occur. A sore, red, and smooth tongue (glossitis) is another common complaint.
Numbness or tingling, often described as “pins and needles,” can occur in the hands and feet. Dizziness or lightheadedness are also common, sometimes with faintness. These varied symptoms arise as the body struggles to function without sufficient vitamin B12.
Observable Physical Signs
Pernicious anemia can also present with several observable physical signs. A distinct pallor of the skin is common, sometimes accompanied by a subtle lemon-yellow tint. This yellowish hue results from a combination of anemia and a mild degree of jaundice due to ineffective red blood cell production.
The tongue may appear unusually smooth, shiny, and beefy red (atrophic glossitis). This change is due to the loss of papillae on the tongue’s surface. Some individuals might also exhibit a rapid heart rate (tachycardia) or even develop a heart murmur, as the heart works harder to compensate for reduced oxygen delivery.
In some cases, the spleen may become mildly enlarged (splenomegaly). Subtle changes in gait or balance issues can also be observed, hinting at neurological involvement. These physical manifestations provide objective clues to the presence of the condition.
Neurological Manifestations
Prolonged vitamin B12 deficiency can lead to specific and severe neurological and psychiatric complications. Peripheral neuropathy is a common neurological manifestation, involving numbness, tingling, or burning sensations, particularly in the extremities. This can progress to muscle weakness and spasticity in more advanced stages.
Difficulty with balance and coordination, medically termed ataxia, can impair walking steadily. Cognitive impairments are also observed, presenting as memory problems, confusion, and “brain fog”. These can range from mild forgetfulness to more significant cognitive decline.
Mood changes, including irritability and depression, are recognized psychiatric symptoms. In severe and untreated cases, more profound mental health issues, such as psychosis, can develop. Vision problems, specifically optic neuropathy (damage to the optic nerve), can also occur.
Diagnostic Confirmation
Confirming pernicious anemia involves specific tests that reveal vitamin B12 deficiency and its cause. Blood tests are the primary method for diagnosis, starting with a Complete Blood Count (CBC). This test typically shows macrocytic anemia, indicating larger-than-normal red blood cells, along with a low red blood cell count and low hemoglobin levels.
Measuring serum vitamin B12 levels directly reveals a deficiency. To differentiate pernicious anemia from other causes of B12 deficiency, additional markers are assessed. Elevated levels of methylmalonic acid (MMA) and homocysteine in the blood are specific indicators of vitamin B12 deficiency, as these substances accumulate when B12 is lacking.
The definitive diagnosis involves testing for intrinsic factor blocking antibodies and/or parietal cell antibodies. These antibodies are hallmarks of the autoimmune attack against intrinsic factor or the stomach cells that produce it. While rarely needed, a bone marrow examination might show megaloblastic erythropoiesis, reflecting abnormal red blood cell development.