What deficiency is associated with a lack of cobalamin (B12)?

The deficiency associated with a lack of cobalamin (Vitamin B12) is indeed pernicious anemia. This condition arises specifically due to an inability to absorb B12 from the gastrointestinal tract, often linked to a lack of intrinsic factor, a protein necessary for B12 absorption.

Individuals with pernicious anemia can experience symptoms such as fatigue, weakness, memory problems, and neurological issues due to the critical role of B12 in red blood cell formation and neurological function. The condition is characterized by the formation of large, abnormal red blood cells, which is also a hallmark of megaloblastic anemia, but the defining point of pernicious anemia is the absorption issue rather than just the presence of large cells.

While megaloblastic anemia is indirectly related to B12 deficiency, as it presents with similar symptoms and abnormal blood cell size, it does not encompass the absorption challenge that defines pernicious anemia. Rickets is primarily associated with vitamin D deficiency, and scurvy is caused by a lack of vitamin C; thus, these conditions are unrelated to cobalamin deficiency.