Pneumocystis carinii pneumonia (PCP) is an opportunistic lung infection caused by the fungus Pneumocystis that primarily affects those with weakened immune systems, especially those with advanced HIV/AIDS. It presents with cough, shortness of breath, fever, and lung infiltrates. Before the 1980s AIDS epidemic, it was rare and mainly affected those with malnutrition, leukemia, or on corticosteroids. Diagnosis involves staining sputum or bronchoalveolar lavage samples to identify the characteristic cysts and trophozoites of Pneumocystis under a microscope.

1. Pneumocystis carinii
Pneumonia
 Pneumocystis carinii pneumonia (PCP)
is an opportunistic infection that occurs in
immunosuppressed populations, primarily
patients with advanced human
immunodeficiency virus infection.

2. The classic presentation of
nonproductive cough, shortness of
breath, fever, bilateral interstitial
infiltrates and hypoxemia does
not always appear

3.  Before the epidemic of acquired
immunodeficiency syndrome (AIDS)
in the early 1980s,

4. Pneumocystis carinii pneumonia
(PCP) was a rare infection that
occurred in immunosuppressed
patients with protein malnutrition or
acute lymphocytic leukemia, or in
patients receiving corticosteroid
therapy.

6. Risk Factors and Clinical
Presentation
Defective T-cell immunity is the
primary risk factor for PCP.
 Associated clinical signs are well
defined in HIV infection and
reflect the degree of CD4+ cell
depletion

7. Physical findings are also
nonspecific.
 fine dry rales or may be
unremarkable.
In 2 to 6 percent of cases, PCP
may present with a spontaneous
pneumothorax.

8. Extrapulmonary pneumocystosis
occurs rarely, involving organs
such as the heart, skin, spleen,
thyroid or eyes.

9. The chest film typically shows
diffuse interstitial infiltrates but
can be normal in at least one
third of cases.

10. Less commonly, lobar infiltrates,
effusions or cavitary lesions mimic
other pulmonary processes.

11. Many other diseases may have a
similar presentation, including
mycobacterial, fungal, viral or
bacterial pneumonias, heart
failure, Kaposi's sarcoma and
pulmonary emboli.

12. Diagnosis
 P. carinii cannot be routinely cultured
and is identified by stains
demonstrating the cyst wall or the
trophozoite.
 Before the emergence of AIDS, PCP
was diagnosed by open lung biopsy.

13. Less invasive procedures-sputum
induction and bronchoalveolar
lavageare now the methods of
choice

14. Periodic acid-Schiff and
Papanicolou stains have been
used to display the characteristic
honeycombed froth associated
with P. carinii

15. Papanicolou staining
 It uses a combination of
haematoxylin, Orange G, eosin Y,
Light Green SF yellowish, and
sometimes Bismarck Brown Y.

16. PAS staining
 is a staining method used to etect
glycogen in tissues

17. The reaction of periodic acid
selectively oxidizes the glucose
residues, creates aldehydes that react
with the Schiff reagent and creates a
purple-magenta color

18. Solutions and Reagents:
0.5% Periodic Acid Solution:
 Periodic acid 0.5 g
 Distilled water 100 ml