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Pneumocystis Pneumonia
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Pneumocystis Pneumonia

Topics / Medical / HIV and related conditions

Basics

Let us start by saying that the “new name” for this type of pneumonia is called PJP (Pneumocystis Jirovecii Pneumonia) and it is NOT called PCP.

This is because P. jirovecii infects humans, while P. carinni infects rats. The other important fact to keep in mind is that the micro-organism is a FUNGUS, NOT a protozoa (this has been known since around 1988). It is mostly found in immunocompromised patients. It may be transmitted from person to person via the airborne route. Similar to Tuberculosis, patients that are immunocompetent may be infected with PJP. However, these patients will not develop the “disease”. These patients remain asymptomatic, and they may become asymptomatic carriers. This is an AIDS defining illness.

It is important to remember that ANY patient who is immunocompromised may be affected. However, it is worth noting that patients who are HIV infected with a CD4+ count < 200 are at high risk of acquiring PJP.  This is the reason why these patients should be started on primary prophylaxis.

Risk Factors: Primary and Secondary Immunosuppressive conditions (Malignancy, HIV, Transplant Recipients, Immunosuppressive Treatment, Steroids)

Once the fungi attaches itself to the alveolar epithelium, the host response causes significant lung injury which results in impaired gas exchange. (Reason why they desaturate).

Presentation

Patients typically present with several weeks of:

  1. Non-productive dry cough
  2. Low grade fever
  3. Progressive dyspnea
  4. Hypoxemia
  5. Respiratory distress
  6. Most of the patients will have normal or clear lung sounds, however, some may have some crackles. Vitals may be deranged such as a tachycardia, tachypnea, fever.
  7. Usually have a CD4 count < 200

Investigations

  1. Bloods:
    1. CD4+ Count and CD4+ Percentage: Usually less than 14 days
    2. Serum Lactate Dehydrogenase (LDH) becomes elevated, nonspecific.
    3. Serum Beta-D-glucan: Found in many fungi’s cell wall therefore nonspecific.
    4. ABG: Respiratory Failure
  2. CXR:
    1. Diffuse bilateral peri-hilar interstitial infiltrates
    2. Multiple ling nodules which may become cavities
    3. Pneumothorax
  3. CT Chest:
    1. Ground glass opacities
    2. Cystic lesions
  4. Sputum (Definitive Diagnosis)
    1. Polymerase Chan Reaction (PCR)
    2. Dye stains (Microscopy)
    3. Fluorescein Antibody stain (Microscopy)
    4. NB: Keep in mind that a definitive diagnosis for PJP is not always possible. 
Chest Xray of PJP
Case courtesy of Dr Andrew Dixon, Radiopaedia.org. From the case Pneumocystis pneumonia

Treatment

Only start treatment once a diagnosis is made. However, you may inititate treatment in patients that have risk factors and have features which suggests PJP.

  1. Oxygen supplementation eg Nasal prongs, Facemask as needed
  2. If the patient is hypoxic: Prednisone PO 80mg PO daily for 5 days, then taper over 16 days. For instance:
    1. Prednisone 40mg PO BD for 5 days then
    2. Prednisone 20mg PO BD for 5 days then
    3. Prednisone 10mg PO BD for 11 days
  3. High dose Co-trimoxazole:
    1. Co-trimoxazole 80/400mg PO 6 hourly for 21 days.
      • If the patient is > 60kgs then give the patient three tablets. This is written as Co-trimoxazole 1920mg PO 6 hourly for 21 days)
      • If the patient is < 60kg then give the patient 4 tablets. This is written as Co-trimoxazole 1440mg PO 6 hourly for 21 days)
    2. Monitoring:
      1. Patients should be monitored clinically for the improvement which is excepted to occur after 4 – 8 days while on treatment.

Important

  1. Some patients may develop adverse reactions/allergic reactions to Co-trimoxazole, such as Stevens-Johnson. In this case you may consider changing it for Clindamycin plus Primaquine or Dapsone may be used.
  2. Remember that if the patient is vomiting you may also give Co-trimoxazole IV 6 hourly (the dose is also different)
  3. Steroids have be proven to increase cinical outcome and mortality.
  4. Always remember: If the patient is HIV positive, then initiate ARV treatment (if the patient is newly diagnosed) within 2 weeks from starting the PJP treatment. Once the patient has completed the 21 day high dose co-trimoxazole, then one needs to continue low dose co-trimoxazole as prophylaxis until at least 6 months AND the CD4+ count is > 200.
  5. Other indications for steroid use: From NCBI, “Room air arterial blood gas partial pressure of oxygen that is less than or equal to 70 mm Hg, an alveolar-arterial (A-a) gradient greater than or equal to 35 mm Hg, or hypoxia on pulse oximetry”.
Published on 26 July 2022
Dr. RW Becerra Estevez
Dr. RW Becerra EstevezMBChB (WSU)

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