Which clinical sign could indicate untreated B12 deficiency?

Glossitis, which is the inflammation of the tongue, can indeed indicate untreated vitamin B12 deficiency. In individuals with B12 deficiency, especially when it progresses, the tongue may become swollen, painful, and exhibit a smooth, red appearance due to the loss of papillae, which are responsible for texture. This is a direct result of the role vitamin B12 plays in maintaining the health of the mucosal membranes. Additionally, glossitis can occur alongside other symptoms of deficiency, such as fatigue, neuropathy, and anemia, reinforcing its significance as a clinical sign.

While pernicious anemia is a related concept—it specifically refers to the autoimmune condition leading to a lack of intrinsic factor necessary for vitamin B12 absorption—glossitis directly reflects the deficiency's impact. Diabetes and hyperthyroidism are not associated with vitamin B12 deficiency; they represent different metabolic disorders entirely. Thus, glossitis serves as a clear, observable sign of B12 deficiency that can prompt further investigation and management.