Rasmussen aneurysm is a distinctive variant of

pseudoaneurysm A pseudoaneurysm, also known as a false aneurysm, is a locally contained hematoma outside an artery or the heart due to damage to the vessel wall. The injury passes through all three layers of the arterial wall, causing a leak, which is contai ...

of a branch of the

pulmonary artery A pulmonary artery is an artery in the pulmonary circulation that carries deoxygenated blood from the right side of the heart to the lungs. The largest pulmonary artery is the ''main pulmonary artery'' or ''pulmonary trunk'' from the heart, and ...

, predominantly found adjacent to or within a lung cavity, both often arising as a complication of

pulmonary tuberculosis Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...

. The condition was originally described by Fritz Valdemar Rasmussen in 1868. It is a relatively uncommon complication associated with cavitary tuberculosis of the lung, with its

prevalence In epidemiology, prevalence is the proportion of a particular population found to be affected by a medical condition (typically a disease or a risk factor such as smoking or seatbelt use) at a specific time. It is derived by comparing the number o ...

observed in approximately 5–8% of cases based on autopsy findings. It is caused by the progressive thinning of the pulmonary artery wall. This weakening process is characterized by the replacement of both the

tunica externa The tunica externa (Neo-Latin "outer coat"), also known as the tunica adventitia (Neo-Latin "additional coat"), is the outermost tunica (biology), tunica (layer) of a blood vessel, surrounding the tunica media. It is mainly composed of collagen an ...

and

tunica media The tunica media (Neo-Latin "middle coat"), or media for short, is the middle tunica (layer) of an artery or vein. It lies between the internal elastic lamina of the tunica intima on the inside and the tunica externa on the outside. Artery The ...

with

granulation tissue Granulation tissue is new connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process. Granulation tissue typically grows from the base of a wound and is able to fill wounds of almost any size ...

, which subsequently undergoes transformation into

fibrin Fibrin (also called Factor Ia) is a fibrous protein, fibrous, non-globular protein involved in the Coagulation, clotting of blood. It is formed by the action of the protease thrombin on fibrinogen, which causes it to polymerization, polymerize. ...

. This tissue remodeling is a consequence of the healing response in the associated lung cavity. The dilation of the pulmonary artery in close proximity to or involvement within the lung cavity leads to the formation of a pseudoaneurysm. As is typical with any

aneurysm An aneurysm is an outward :wikt:bulge, bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also b ...

, Rasmussen aneurysm carries the inherent risk of rupture, which may result in life-threatening massive

hemoptysis Hemoptysis or haemoptysis is the discharge of blood or blood-stained sputum, mucus through the mouth coming from the bronchi, larynx, vertebrate trachea, trachea, or lungs. It does not necessarily involve coughing. In other words, it is the airw ...

, characterized by the coughing of blood. Such events are associated with a mortality rate exceeding 50%. Historically, Rasmussen aneurysms were widely regarded as a common etiology of hemoptysis, particularly in tuberculosis cases. However, with advancements in

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting pathogenic bacteria, bacterial infections, and antibiotic medications are widely used in the therapy ...

therapy and improvements in medical knowledge, contemporary understanding has evolved. Current medical insight suggests that the majority of hemoptysis cases are more closely linked to bleeding originating from the systemic

bronchial arteries In human anatomy, the bronchial arteries supply the lungs with oxygenated blood, and nutrition. Although there is much variation, there are usually two bronchial arteries that run to the left lung, and one to the right lung, and are a vital part ...

within the lung, with pulmonary artery aneurysms accounting for less than 10% of cases. This shift has led to a significant alteration in the approach taken by medical professionals in the diagnosis and management of hemoptysis within clinical practice. ''Rasmussen aneurysm'' was initially associated exclusively with cavitary tuberculosis, but the term is now utilized to encompass any anatomical aneurysm occurring in conjunction with various forms of destructive lung lesions.

References

{{reflist Vascular diseases Tuberculosis