Study of Pneumocystis carinii infection in paediatric autopsies (report of 3 cases).
Pneumocystis carinii is a ubiquitous organism that infects human beings by the respiratory route. The organisms appear to be relatively avirulent since they usually cause disease in immunodeficient individuals.
In children P. Carinii infection is known to associate with congenital immunodeficiency syndromes as well as protein caloric malnutrition. In premature babies infection is common at 3-5 months' age since their IgG levels are low. Reports from developed countries show a rising incidence of P. Carinii due to control of bacterial infections and improved survival of moriband patients as well as premature babies.
Since malnutrition and prematurity are commonly encountered in paediatric autopsies at our place it was thought worth-while to survey for infection by P. carinii in autopsy material.
Material was collected from lungs of 250 paediatric autopsies done during a one year period. Imprint smears from cut surface of fresh lungs were collected at the time of autopsy and fixed in 1:1 ether-alcohol mixture. These were stained by Giemsa stain. Five tissue blocks of lung-one from each lobe, were fixed in buffered formaline and processed to get 5 A thin, paraffin sections. These were stained by H & E., P.A.S. and Gomori's silver methanamine stains. Clinical data and other autopsy findings were recorded. All sections and smears were thoroughly examined under high power and 1000 magnification for presence of Pneumocystis carinii cysts and organisms.
Out of 250 paediatric autopsy cases studied, only 3 cases revealed infection by P. carinii. The details of these three cases are presented below:
A 3 month old female baby was admitted for convulsions. She had multiple congenital anomalies, hypocalcemia and oral thrush. Clinically, DiGeorges, syndrome was suspected. Autopsy revealed total situs inversus, palatal defect, short neck and hypoplastic thymus. The parathyroids could not be traced. There was oral thrush, pyogenic meningitis and consolidation of lungs.
A 15 month old male baby was admitted for post-measles bronchopneumonia. The patient had a fall from the cot. His post mortem examination revealed severe marasmus, bronchopneumonia and subarachnoid haemorrhage. The thymus was atrophic and revealed lymphocyte depletion on histology.
A one and half month old male infant was admitted for respiratory difficulty. He was a premature baby and weighed 2 kg at the time of admission. The lungs revealed patchy consolidation. The thymus showed scanty lymphocyte zone.
Microscopic examination of lungs revealed bronchopneumonia in the 1st two cases and interstitial pneumonia in the 3rd case. In addition, in all the three cases there were focal groups of alveoli exhibiting Pneumocystis carinii. These alveoli, on H. & E. stain, appeared filled with pale, eosinophilic, foamy, honeycombed material [Fig. 1]. Scattered tiny nuclei of trophozoites were seer, in the exudate. The alveolar septae were thickened and infiltrated by plasma cells, lymphocytes and histiocytes, G.M.S. stain was found the best for demonstration of cysts which were round or cup-shaped and measured 3-5 u [Fig. 2].
The ruptured cysts resembled collapsed grape-skins. P.A.S. stain showed 4-8 trophozoites in each cyst but the contrast was not good. Various stains were employed on smears of pulmonary aspirates for diagnosis of P. carinii. Giemsa stain showed all three phases of the organism; hence, it was preferred in this study; however, it did not give satisfactory results as the imprint smears of the lung surface were heavily mixed with blood and other cell components.
Pneumocystosis is a disease caused by protozoan parasite P. carinii which grows in pulmonary alveoli in immunodeficient patients. Clinically pneumocystosis manifests as interstitial pneumonia. The respiratory distress is out of proportion to physical signs. The diagnosis is based on demonstration of proliferating organism in the lung tissue (aspiration biopsy or autopsy) or sputum. The lesions are common in the subpleural zones of the dependent parts.
P. carinii exists in trophozoite, precyst and cyst forms. The life cycle is complete in four hours and is well described.
Pneumocystis pneumonia is usually associated with hematologic neoplasia or organ transplantation, although widespread use of immunosuppressive chemotherapy especially corticosteroids has facilitated its occurrence in patients with wide range of neoplastic and inflammatory diseases. The incidence of reported cases seems to be rising with the advent of premature baby nursaries, intensive care units and control of bacterial diseases.
Two basic forms of P. carinii infection are considered (a) Infantile focal or generalised pneumocystosis with plasma cell pneumonia due to IgG and probably IgA deficiency. Complement fixation test becomes positive in these cases after 3-6 weeks of infection. There is no recurrence in this type; (b) Hypoergic or hypoimmune pneumocystosis due to congenital abscence of IgG or iatrogenic immune deficiency. There is no plasma cell response. The organisms can be destroyed by drugs but recurrence is common. The complement fixation test remains negative. In a large series of pneumocystis pneumonia the attack rate of in children under one year of age was found to be five times higher than other age groups.
In children, pneumocystosis has also been reported with primary congenital immunodeficiency syndromes. One of our cases was associated with DiGeorges' syndrome i.e. defective development of parathyroid and thymus. Our patient manifested hypocalcemia. The infant also had candida infection.
The second case was convalescing from measles infection which might have depressed the T cell function. The third one was severely malnourished and weighed only 2 kg at the age of 40 days. The immunoglobulin levels and C.M.I. functions were not done.
The thymus was markedly hypoplastic in the 1st case and atrophic in the other two. Rest of the lymphoid tissue in the body was scanty. Although association between immune deficiency and P. carinii infection is poorly understood, defects in both humoral and cellular immunity appear to be operative.
The lungs of the cases revealed interstitial pneumonia as well as areas of bronchopneumonia indicating double infection.
The cases reported from S. Africa by Hughes and Shiraz Study revealed associated bacterial infection. While others accept diagnosis of P. carinii pneumonia only if abundent P. carinii organisms are present associated with an inflammatory response and if no other co-existant organisms are demonstrated by pathological examination, cultivation or serologic methods.
In spite of frequency of P.E.M. at our place, Pneumocystis carinii is detected in only 1.2% of autopsied cases probably due to high death toll taken by bacterial infections.
The project was supported by the Research Society, Seth G.S. Medical College and K.E.M. Hospital. The author is thankful to the Dean, Seth G.S. Medical College and K.E.M. Hospital for permitting me to publish the material and to Smt. Bharati Hardikar for technical help.