Final answer:
A pustule contains pus and is often related to suppurative skin infections like acne and impetigo.
Step-by-step explanation:
A pustule is a raised, inflamed papule with a white or yellow center containing pus in the top of the lesion. Pus is a thick, yellowish or greenish opaque liquid produced in infected tissue, consisting of dead white blood cells, bacteria, tissue debris, and serum. It is most commonly associated with suppurative (pus-producing) infections of the skin, such as acne, impetigo, furuncles, and carbuncles.
For instance, in the context of acne, an infection by Propionibacterium acnes can result in inflammatory lesions such as papules, pustules, nodules, or pseudocysts. Furthermore, impetigo, which is often caused by Staphylococcus aureus, S. pyogenes, or a combination of both, leads to the formation of vesicles, pustules, or bullae that rupture to produce encrusted sores.