User:Produde29499/Asthma-COPD Overlap Syndrome

Asthma-COPD Overlap Syndrome (ACOS) is a chronic inflammatory, obstructive airway disease in which features of both Asthma and COPD are present. Asthma and COPD were once thought of as distinct problems, however in some people, there are clinical features of both asthma and COPD with significant similarity in pathophysiology and symptoms. It is unclear whether ACOS is a separate disease or a clinical subtype of Asthma and COPD. The pathogenesis of ACOS (the process by which an infection leads to a disease) is badly understood, but it is thought to involve a special type of inflammation (usually seen in asthma) as well as another type of Inflammation (this time seen in COPD). The incidence and prevalence of ACOS are not well known. The risk factors for ACOS are also incompletely understood, but tobacco smoke is known to be a major risk factor.

Signs and symptoms

ACOS presents with symptoms of both Asthma and COPD. ACOS presents in adulthood, usually after the age of 40 (after there has been significant smoke exposure), with symptoms of dyspnea (shortness of breath), inability to exercise, mucus production, cough and episodes of worsening (exacerbations).

Cause

A history of significant and persistent smoke exposure is required for the diagnosis of COPD, therefore is also required for the diagnosis of ACOS. This can be due to smoking and air pollution.

Pathophysiology

ACOS has features of both asthma and COPD. Both asthma and COPD (as well as ACOS) present with attacks, periods where symptoms deteriorate, with reductions in airflow. However, in asthma, the airflow limitation usually completely resolves after exacerbations, whereas in COPD it may not. ACOS presents with a lot of airway clogging (due to inflammation), with symptoms of both asthma and COPD. Inflammation of the large and medium airways (classically seen with Asthma) is seen in ACOS. This consists of airway tightening due to the smooth muscle in your airway tightening the airway as well as the smooth muscle overreacting (due to allergens or irritants) causing a blocked airway. Mucus production and swelling in the airways can also cause airway obstruction in asthma.

Features of COPD (which include types of severe bronchitis and COPD) are also seen in ACOS. These include the features of severe bronchitis such as swelling of the small airways and mucus production. Bronchiole inflammation may lead to pulmonary fibrosis. As well as features of emphysema including swelling leading to alveolar destruction resulting in extreme lung swelling and air trapping.

Diagnosis

There are no widely accepted diagnostic criteria for ACOS, however the diagnosis requires clinical features of both asthma and COPD. One criteria, based on expert consensus,requires the presence of 3 major and at least 1 minor criteria for the diagnosis of ACOS. The major criteria are: a persistent airflow blockage, a significant history of smoking, or significant exposure to other indoor or outdoor air pollution and a history of asthma. The criteria include a history of allergic rhinitis, a worse response to an inhaler. Spirometry (documenting blockage) is required for the diagnosis of ACOS.

In those with asthma, some features often seen in COPD that may aid in the diagnosis of ACOS include emphysema seen on imaging. In those with COPD, other features often seen in asthma that may aid in the diagnosis of ACOS include an increase in the fraction of exhaled nitric oxide.

Treatment

Treatment of ACOS is based on expert opinion as there are no universally accepted guidelines from a Clinic. Treatment is usually based on whether features of Asthma or COPD dominate. Inhalers are the primary treatment in those with ACOS. Inhalers should be continued in those with Asthma who develop decreased airway responsiveness to bronchodilators consistent with ACOS. Therapy can be escalated to include a long lasting inhaler that prevents Asthma (usually an inhaler that has an orange case cover) and a combination or by having triple therapy, in those with more severe or resistant disease.

Monoclonal antibodies targeting a type of inflation which is predominant in Asthma have been used to treat severe asthma, and may also be used in severe cases of ACOS. These Antibodies include omalizumab (an Anti-inflammitory antibody), mepolizumab (an anti-inflammitory antibody) and benralizumab (another Anti-inflammatory antibody). People with ACOS and eosinophilia have a better response to them with fewer exacerbations and hospitalizations seen in ACOS treated with long term antibodies. Corticosteroids injected, or mouth drugs may be used during exacerbations of ACOS.

Prognosis

The progression of permanent airflow blockage is slower in ACOS as compared to COPD, but ACOS with late onset asthma is associated with a more rapid progression of blockage and a worse prognosis. ACOS with late onset asthma is associated with a higher chance of death as compared to COPD, asthma or healthy controls. Excluding ACOS with late onset asthma, ACOS has better survival than COPD, but higher chance of death compared to asthma. In other studies, ACOS was associated with worse dyspnea symptoms, more coughing, wheezing, mucus production as well as more frequent and more severe exacerbations as compared to COPD or asthma.

Epidemiology

Due to the diversity of criteria and a small quantity of trials, the prevalence of ACOS is not well known. Based on an analysis, the prevalence of ACOS in the general population is estimated to be 2%, whereas the prevalence of ACOS in those with asthma is 26.5% and in those with COPD it is 29.6%.