Angina bullosa hemorrhagica (ABH) is the term used to describe acute, benign, and generally subepithelial oral mucosal blisters filled with blood that are not attributable to a systemic disorder or hemostatic defect. [1, 2, 3]
This condition was first described in 1933 as traumatic oral hemophlyctenosis. Badham first used the currently accepted term angina bullosa hemorrhagica in 1967.
The lesions may be confused with other more serious disorders (eg, mucous membrane pemphigoid, epidermolysis bullosa, linear IgA, dermatitis herpetiformis); however, the isolated nature, rapid healing, and rare recurrence of angina bullosa hemorrhagica blisters generally are sufficient findings to rule out the previously mentioned conditions.
The lesions of angina bullosa hemorrhagica may be indistinguishable from blood blisters related to thrombocytopenia; however, blood tests and the absence of areas of ecchymosis, epistaxis, or gingival bleeding are helpful signs to rule it out.
Some authors suggest mild trauma as the causative agent in angina bullosa hemorrhagica to break the epithelial–connective-tissue junction, causing bleeding of superficial capillaries and resulting in the formation of a subepithelial hemorrhagic bullae.
A genetic predisposition of loose adhesion between the epithelium and corium of the mucosa or a weak anchorage of the mucosal vessels may result in subepithelial hemorrhage. 
Angina bullosa hemorrhagica (ABH) may also represent an acute or chronic injury to soft tissue. It is an example of an oral mucosal traumatic lesion.  Angina bullosa hemorrhagica most commonly occurs in the soft palate where the covering squamous epithelium of the nonkeratinized type is thin and friable.  The break in the epithelial-connective–tissue junction causes bleeding of the superficial capillaries, resulting in the formation of the subepithelial hemorrhagic bullae. 
Angina bullosa hemorrhagica may also be a rare and underestimated adverse effect of inhalational corticosteroid therapy. The resulting collagen synthesis modifications lead to mucosal atrophy and a decrease in submucosal elastic fibers, especially in the elderly population over the long term (>5 y). Long-term use of such inhalers may induce capillary breakdown. [6, 7] Similarly, vascular fragility has also been implicated, in view of the association of angina bullosa hemorrhagica with diabetes mellitus. 
Angina bullosa hemorrhagica (ABH) is a benign condition; however, some authors have reported acute upper airway obstruction associated with rapidly enlarging bulla of the posterior pharynx and epiglottic region.  Rarely, tracheal intubation and surgical tracheostomy are required in such patients.
No sex predilection is reported for angina bullosa hemorrhagica (ABH).
Angina bullosa hemorrhagica (ABH) predominantly affects middle-aged or elderly people. The median age at presentation is 54 years, with 60% of the patients in the range of 45-70 years. Lesions have not been documented in children younger than 10 years.