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Allergic Asthma

Asthma is a complex genetic syndrome that affects some 300 million persons in the world. The response to treatment is also genetically complex and is characterized by a high intra-individual repeatability and high inter-individual variability, where 40% of the patients with asthma might not have a response to therapy. Inhaled glucocorticoids (also called inhaled corticosteroids or ICS) are the most prescribed medicines for controlling asthma. The endogenous glucocorticoid levels are inherited and vary at the beginning of the treatment in addition to the response to the variations of the environment. On the other hand, the studies carried out in families with distinct asthma conditions have shown family segregation as well as inherited conditions in the response to glucocorticoids. Given the inheritability within the therapeutic class of glucocorticoids, as well as the high levels of variability between patients and within the repeatability in response to the inhaled glucocorticoids for asthma treatment, it is possible that the response have a genetic base.

The hypothesis of some of the studies by the genome association is to identify new variants associated with the response to inhaled glucocorticoids for asthma. This hypothesis has been put to the test with the use of an algorithm for “detection based on the subjects’ families” randomly assigned inhaled glucocorticoids in the Childhood Asthma Management Program (CAMP). Through this detection SNPs have been identified that offer a greater potential for association which is also reproducible for the response to inhaled glucocorticoids, a measured as a change in the forced expiratory volume in 1 second (FEV1). After the selection, the association of the SNPs of four additional populations, taken from independent clinical trials with asthma patients was assessed.

 

Asthma classification

1. Rackman in 1918-1947

  • Atopic or extrinsic asthma: generally is seasonal and has an evident allergic stimulus; frequently begins in infancy or adolescence and the patient has family antecedents of allergic illnesses (eczemas, rhinitis, rashes). Its incidence is double in men than in women. Extrinsic asthma includes that of those patients having an antigen-antibody reaction that can be demonstrated as a trigger. Generally this antigen-antibody reaction is measured by IgE antibodies (atopic extrinsic asthma) while in other cases usually of occupational origin, a Gell and Coombs Type I hypersensitivity reaction (extrinsic no atopic asthma) cannot be demonstrated. 90% of the asthmas are atopic.
  • No atopic or intrinsic asthma (unknown cause): patients do no present personal or family antecedents of allergies; the illness appears in adulthood and affects equally both sexes. It is not possible to detect a concrete antigen as a precipitating cause. It usually begin in adult life, in many cases associated with nasal polyps, maxillary sinusitis, and /or idiosyncrasies to aspirin or other non-steroid anti-inflammatories and presents a chronic course that frequently needs oral steroids for its control.

 

2. Special forms of asthma

  • Asthma brought on by exercise: Many patients experience and obstruction of the airways 5 to 20 minutes after stopping the exercise or during the exercise due to a mechanism that seems to include cooling off, relative dryness of the secondary airways on increasing ventilation and the loss of heat in the airways.
  • Occupational asthma: It is produced by inhaling industrial smoke, dust and emissions found in the work place. Four response patterns in occupational asthma have been described: exclusive immediate, exclusive delayed, dual and recurrent nocturnal during several days. These patients, although varied according to the response type shown, usually improve when outside of the work place, during vacation time, weekends and periods of medical absence.

 

3. Classification according the clinical evolution

  • Intermittent or episodic asthma: if the illness involves dyspnoea (difficulty in breathing) with asymptomatic intervals.
  • Chronic or persistent asthma: if the symptoms are more or less permanent and sustained and have periodic exacerbations.

 

4. Classification according to age

  • Infantile asthma: The large majority are of viral origin from the same virus that causes bronchiolitis.
  • Childhood asthma: Boys are more affected than girls and is associated with allergies to allergens in the majority of cases.
  • Adolescent asthma: It is characterized by symptom and therapeutic regimen negation and the rate of mortality is greater at this age.
  • Adult asthma

Symptoms

The majority of persons with asthma have attacks separated by asymptomatic periods. Some people have prolonged difficulty in breathing with episodes of increased lack of breath. A whistling, wheezing or cough could be a principal symptom.

Asthma attacks can last minutes to days and can become dangerous if the airflow is severely restricted.

Attack symptoms include:

  • A cough with or without mucus (phlegm) production
  • Pulling of the skin between the ribs when breathing (Intercostal retractions)
  • Difficulty breathing which worsens with exercise or activity
  • Whistling sound when exhaling
  • Blue tinge to face or lips
  • Diminishing of mental lucidity, intense drowsiness or confusion during an asthma attack
  • Extreme respiratory difficulty
  • Rapid pulse
  • Intense anxiety due to breathing difficulties
  • Sweating
  • Abnormal respiratory pattern where exhaling (breathing out) takes more than twice as long as inhaling (breathing in)
  • Breathing temporarily stops
  • Chest tightness or pain

Prevention

Asthma symptoms can be substantially reduced avoiding triggers and substances that irritate the airways.

  • Use allergy-proof bedding to reduce exposure to dust mites
  • Vacuum bedroom carpets, rugs and furniture regularly
  • Use only fragrance-free detergents and cleaning products
  • Keep humidity levels low and repair leaks which can lead to the growth of mold
  • Keep the home clean and keep food in closed containers and out of the bedrooms to avoid the possibility of roaches as these can be triggers of asthma attacks in some people.
  • If a person is allergic, keep household pets out of the bedroom and use filters on heating ducts to trap animal dander.
  • Eliminate tobacco smoke. This is the most important step a family can take to help a person with asthma. Smoking outside of the house is not sufficient as the family members who smoke outside bring smoke residue inside on their clothes and in their hair, causing an asthma attack.

 

Persons with asthma should avoid as much as possible areas of environmental pollution, industrial emissions and other irritating emissions.

Gene or region studied

  • 17q21.32
  • TLR2
  • TBX21
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