HIV Pneumonia

What is HIV pneumonia?

Pneumonia is an infection of the lung that can occur in any person. It is more likely to affect people with weakened immune systems. HIV infection is one of the rapidly growing causes of a weak immune system. Therefore pneumonia in an HIV-positive patients is sometimes termed HIV pneumonia or more correctly as HIV-associated pneumonia. It is similar to pneumonia in any other person although sometimes in HIV pneumonia the microorganisms that causes the infection are very rare. When pneumonia occurs in HIV or any other diseases that compromises a person’s immune status, there is a high degree of mortality. This means that the chances of death is very likely especially if medical treatment is not rapidly initiated.

HIV Pneumonia Reasons

HIV Infection

The human immunodeficiency virus (HIV) is transmitted through contact with body fluids. Once the virus enters the bloodstream of a person, it targets certain types of immune cells known as CD4+ T-lymphocytes. The virus enters these cells, utilizes its resources to replicate and eventually destroys the cell. Gradually the population of the CD4+ cells decreases thereby compromising the body’s immune defenses. At the same time the number of virus particles in the bloodstream increase exponentially and is able to destroy more CD4-cells.

The process is ongoing and after several months to years, the body’s immune defenses are compromised to a state where it is prone to all types of infections. Many of these infections can be mild in a person with a healthy immune system, but in the backdrop of HIV infection it causes severe disease. When the body’s immune defenses drops to a very low state and otherwise rare infections and cancers appear, the person is said to have AIDS (acquired immune deficiency syndrome).

Pneumonia in HIV Infection

Most infectious agents that cause pneumonia reach the lung through the airways. Bacteria are the most common pathogens, followed by viruses and fungi. The airways have numerous protective mechanisms in place to neutralize pathogens before it reaches the lungs. Tiny hairs and mucus produced by the lining of the airways traps microbes, and neutralizes it as well as pushes it out of the respiratory tract. However, it is still possible for microorganisms to reach all the way to the lungs. Sometimes the invading pathogen reaches the lung through the bloodstream from a site of another infection elsewhere in the body. It can also directly spread from infections in neighboring organs.

In a person with a healthy immune system, the local defenses in the air sacs and alveolar septa of the lung tissue will be initiated once the microbe enters. These defenses will then target and destroy the invaders sometimes even before an infection sets in. Should an infection arise (pneumonia) then treatment is necessary to assist the immune system in it fight against the invader. Eventually a person will recover from the infection. The process is not as simple and straightforward with HIV infection as medication may be able to combat the invader but without an adequately functioning immune system, recovery is temporary or not complete.

HIV Pneumonia Causes

Pneumonia is caused by viruses, bacteria or fungi. HIV infection simply lowers the immune defenses sufficiently to allow these infections to occur more easily and persist for longer. In addition, otherwise rare microorganisms particularly certain fungi, are more likely to cause pneumonia in a person who is HIV-positive or has AIDS. Some of the pathogens that are likely to cause HIV associated pneumonia includes :

Bacteria

  • Mycobacterium tuberculosis
  • Mycobacterium avium
  • Streptococci, particularly Streptococcus pneumoniae

Fungi

  • Pneumocystis (carinii) jiroveci – most common opportunistic infection in HIV
  • Coccidioides immitis (coccidiomycosis)
  • Histoplasma capsulatum (histoplasmosis)
  • Cryptococcus neoformans (cryptococcosis or cryptococcal pneumonia)

Viruses

  • Herpes simplex virus
  • Varicella zoster virus

HIV Pneumonia Types

The different types of pneumonia are essentially infection and inflammation of the lung caused by the various bacteria, viruses and fungi.

Mycobacterium Pneumonia

Pulmonary tuberculosis associated with HIV infection is a growing problem globally. It is caused by Mycobacterium tuberculosis. Most new TB cases are related to HIV infection. There are two forms of TB infection – active infection and latent infection. In the active infection, the bacilli are destroying lung tissue while in latent infection the bacilli are encased within the lung and not attacking the lung tissue. HIV is one of the major risk factors for tuberculosis in this day and age and active infection is more likely to be seen in HIV-positive patients.

Mycobacterium avium complex (MAC) infection may occur with one of two Mycobacterium species – Mycobacterium avium and Mycobacterium intracellulare. Pneumonia is more likely to occur without reactivation of a latent infection as may be the case with the pulmonary tuberculosis. It is uncommon among people who are not immune compromised.

Fungal Pneumonia

A number of fungi can cause pneumonia that is rarely ever seen in a person who is not immunocompromised. The trophic form or spores of these fungi travel down the airways to lodge in the lung. Sometimes there is a latent infection where the fungi is present in the lungs but not actively damaging the lung tissue until the immune defenses are compromised. These forms of pneumonia includes coccidiomycosis, cryptococcus, histoplasmosis and  Pneumocystis (carinii) jiroveci pneumonia (PCP). Prior to the use of antiretrovirals for HIV infection, PCP was seen in the majority of HIV-positive patients.

Bacterial Pneumonia

Bacteria are the main cause of pneumonia. Streptococcus pneumoniae is the most common bacterial pathogen, both in HIV-positive and seronegative patients. However, a person living with HIV is more likely to develop pneumonia when this bacteria gains entry into the lung.

Viral Pneumonia

The two main viruses are implicated in HIV-associated pneumonia is herpes simplex virus (HSV) and varicella-zoster virus (VZV).  These infections are not common even in HIV-positive patients. Varicella zoster is the virus that causes chickenpox and a reactivation of the infection, which commonly causes shingles in adults, can lead to pneumonia in immunocompromised patients.

HIV Pneumonia Symptoms

The main symptoms of pneumonia includes a cough, difficulty breathing and chest pain. Other symptoms like fever and weight loss may be seen in HIV infection even without pneumonia. However, these symptoms are also a part of pneumonia.

Cough

The early stages of pneumonia may present with a productive cough. This means that mucus is produced and coughed up (sputum). Bloody mucus is more often seen with tuberculosis but can occur in any infection. A rusty red colored mucus may be seen with Streptococcus pneumoniae infection. A non-productive cough is more likely in AIDS patients.

Breathing

Difficulty breathing may be variable. Initially it starts off at exertional dyspnea where a person only experiences significant difficulty breathing after physical activity. Over time the dyspnea gets worse to the point that it is present even at rest. In severe cases the patient may be in respiratory distress and this has a poor prognosis for HIV-positive patients.

Chest Pain

Pneumonia typically causes pleuritic chest pain. The pain is sharp and mainly felt when breathing in deeply and during coughing. However, some patients may feel pain constantly. Abdominal pain may also be present although this may be due to other conditions, particularly of the abdominal organs.

HIV Pneumonia Diagnosis

Patients with pneumonia may present with the following signs :

  • Rapid breathing
  • Rapid or slow heart rate
  • Abnormal breathing sounds, including decreased breath sounds
  • Percussion dullness
  • Increased vocal resonance (egophony)

The symptoms along with the signs mentioned above and the medical history may be sufficient to reach a differential diagnosis of pneumonia. Specific tests need to be done to including blood tests, sputum culture and cytoscopy, and sometimes blood cultures. Imaging studies like X-rays and CT scans are useful in identifying lung changes associated with pneumonia like consolidation of a lobe of the lung. Removal of fluid from the lungs (thoracocentesis) can also be helpful with diagnosis once the aspirated fluid is examined and tested.

Blood Tests

Blood tests are useful for confirming an infection and assessing the patient’s status. It is usually not conclusive for the type of pneumonia. These tests can also be used to monitor the progression of the diseases and response to treatment.

Sputum Tests

This is the preferred method of diagnosing the cause of pneumonia and is conclusive in the diagnosis when considered along with  the resul0st of blood tests, x-rays and the history. Sputum culture is where the sputum sample is used to grow the causative organism on media within the laboratory. The organism can then be identified and its sensitivity to certain antibiotics can be verified thus aiding in the treatment. Sputum cytology is the microscopic examination of the sample and may also be of use in verifying the causative pathogen and degree of lung damage.

HIV Pneumonia Treatment

Patients with pneumonia first need to be stabilized. Oxygen levels and heart function needs to be monitored. Administration of oxygen may be necessary. Medication is needed both for pneumonia and HIV infection, if the appropriate treatment for the latter has not been started as yet.

  • Antibiotics are mainly used for treating pneumonia. The dosage may be higher and the duration longer in HIV positive patients depending on the severity of the infection and the patient’s immune profile.
  • Antiretroviral therapy (HAART) needs to be commenced in the event of opportunistic infections or patients with a poor immune profile. These drugs need to be used exactly as prescribed.
  • Other measures like corticosteroids and even antivirals (not antiretrovirals) are generally not recommended for HIV patients.
  • Strict bed rest, plenty of fluids and a healthy diet with sufficient protein is also necessary for patients who are not hospitalized. The appropriate supportive measures are implemented within the hospital environment for hospitalized patients.

HIV Pneumonia Death

Before the advent of antiretrovirals, PCP occurred in 70% to 80% of patients. This has significantly decreased in recent years with HAART. It still remains one of the leading causes of death among HIV/AIDS patients.

However, it is important to note that in terms of these statistics it was found that about half of all the patients who died due to PCP were either not using antiretrovirals or not adhering to the regimen. Therefore prophylaxis (medication used for prevention of future infections) may be prescribed in high risk patients who are not responding well to antiretroviral therapy.

Tuberculosis also remains one of the significant causes of death among HIV-positive patients. This has reached epidemic proportions in developing nations.

References

1. http://www.merckmanuals.com/home/lung_and_airway_disorders/pneumonia/pneumonia_in_immunocompromised_people.html

2. http://eprints.ucl.ac.uk/6772/1/6722.pdf

3. http://emedicine.medscape.com/article/807846-overview

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