Denatured pearl protein vesicles, also known as hemoglobin inclusion bodies, are actually denatured hemoglobin particles that are generally attached to cell membranes, and most often occur in sensitive individuals following the administration of medications or exposure to chemicals that can lead to the denaturation of Hb. This inclusion body is also seen in some patients with unstable Hb, and is therefore definitive in glucose-6-phosphate dehydrogenase deficiency as well as in unstable Hb disease, where the stain stains as a purplish-black granule.