Which of the following is a common condition causing severe weakness and susceptibility to infections?

Leukopenia is characterized by a decrease in the number of white blood cells (WBCs) in the bloodstream, which play a crucial role in the immune system. When leukopenia occurs, the body becomes less capable of fighting off infections, making individuals more susceptible to illnesses. This condition can lead to severe weakness as the body is unable to effectively respond to pathogens, leading to an increased risk of infections.

In contrast, while thrombocytopenia relates to a low platelet count and can lead to bleeding issues, it does not directly cause susceptibility to infections in the same way leukopenia does. Anemia involves a deficiency of red blood cells and primarily affects oxygen delivery to the body, leading to fatigue but not necessarily increasing infection risk. Hyperglycemia refers to high blood sugar levels and can lead to various complications, particularly in diabetes, but it does not inherently cause severe weakness or compromise the immune response to the extent seen in leukopenia.