F.AKID, H.FOURATI, E.DAOUD, I.AMMAR, W. FEKI, L.SFAIHI*, M.HACHICHA*, Z.MNIF

Radiology service, Hedi Chaker Hospital Sfax, Tunisia

*Pedaitrics service, Hedi Chaker Hospital Sfax, Tunisia

IMAGING OF CHEST INFECTIONS IN IMMUNOCOMPROMISED CHILD

PEDIATRICS : PD 14

Introduction: The population of children afflicted with primary or

secondary immunodeficiencies is in evolution

This complex and varied population is at high risk for pulmonary complications related to both their underlying disease state and to various treatment regimes

Our purpose is to describe the main imaging appearances of the common infectious complications in immunocompromised children and to emphasize on difficulties in the interpretation of chest imaging in these cases.

Materials and methods:

Didactic poster, showing through a serie explored in our service different aspects of lung infections in children with various immunodeficient states

All patients underwent a chest radiograph and a chest CT scan.

Results:

Case 1:A 4-year-old boy with IL12 deficiency

(A): Frontal chest radiograph demonstrates left upper lobe pneumonia(B, C and D): Axial images from an intravenous contrast-enhanced chest CT, soft-tissue algorithm, show large mediastinal abscesses (arrows), which were drained revealing Mycobacterium tuberculosis. This child also had multiple left lobe lung abscess (arrow head) and a sternal osteolysis.

A B C D

Case 2:

(A): Frontal chest radiograph demonstrates subtle diffuse interstitial opacities caused by Pneumocystis carinii pneumonia.

(B,C): Axial images, lung algorithm, from a CT examination through the chest demonstrates scattered bilateral ground glass and interstitial opacities.

(D): Mosaic appearance with alternating of hyperdense and hypodense areas

A 10-year-old boy with chronic granulomatous disease

A CB D

Case 3:

(A,B and C) Axial images from a chest CT, lung algorithm, shows centrilobular micronodules surrounded by a ground glass appearance mainly at the right lower lobe caused by a candidiasis.

A 4-year-old boy with acute myeloid leukemia

A B C

Case 4:

(A):Frontal Chest Radiograph shows hazy airspace consolidation in the left lung with air bronchogram. Enlargement of soft tissues and interruption of the left costal third anterior arc caused by an aspergillosis

(B and C):Consolidation in the left upper lobe with chest wall invasion. A small consolidation in the middle lobe.

A 6-year-old boy with chronic granulomatous disease

A B C

Case 4:

(A and B):Control CT after 5 months: the pneumonia has not resolved. The chest wall invasion has occasioned parietal abscess (arrow) in front of the consolidation.

A 6-year-old boy with chronic granulomatous disease

A B

Discussion:The immunodeficiency states in children

may be sub-divided into two major groups:

Congenital or primary immunodeficiencie

Acquired or secondary immunodeficiencie

Discussion:Specific thoracic complications vary accordingto the child’s underlying immune status and

specifictreatment protocols. As such, the type of

infection orother disease states encountered depends on :

The child’s type of immunologic abnormality Severity of immunologic deficit Therapeutic interventions Environmental exposures

Primary immunodeficiencies

Humoral immunodeficiencies: The most commonly encountered type of primary

immunodeficiency, accounting for over 70% of all primary immunodeficiencies

Characterized by defective antibody production causing increased susceptibility of affected individuals to recurrent pyogenic infections, particularly caused by encapsulated bacteria, such as Haemophilus influenzae, Streptococcus pneumoniae,and Staphylococci

Primary immunodeficiencies

Humoral immunodeficiencies: Typical manifestations include recurrent pneumonia,

otitis media, sinusitis, and sepsis

Radiographically, children classically demonstrate thoracic abnormalities related to recurrent pulmonary infections including bronchiectasis, bronchial wall thickening, and atelectasis

Bronchiectasis is commonly located in the middle and lower lobes with an upper lobe distribution being unusual

Primary immunodeficiencies

Cellular and combined immunodeficiencies: Patients with cellular immunodeficiencies have increased

susceptibility to disseminated viral and opportunistic infections.

Progressive pneumonia often occurs because of respiratory syncytial virus, parainfluenza 3 virus, Pneumocystis carinii, varicella, or cytomegalovirus

Disorders include DiGeorge syndrome and severe combined immunodeficiency (SCID)

SCID syndrome is characterized by the absenceof both T- and B-cell function

Primary immunodeficiencies

Cellular and combined immunodeficiencies: Chest radiographs may demonstrate narrow upper

mediastinal contour and retrosternal lucency caused by absence of thymic tissue .

Pulmonary complications include recurrent pneumonias cause by P carinii, parainfluenza, respiratory syncytial virus, adenovirus, cytomegalovirus, or bacterial organisms.

Pneumocystis pneumonia typically manifests as diffuse interstitial infiltrates,which may progress to alveolar infiltrates

Primary immunodeficiencies

Partial combined immunodeficiency syndromes:

Partial combined immunodeficiency syndromes encompass a spectrum of disorders with varied clinical manifestations.

These diseases include : Wiskott-Aldrich syndrome, Cartilage-hair hypoplasia, Ataxia-telangiectasia, Purine-nucleoside phosphorylase deficiency, X-linked lymphoproliferative disease

Primary immunodeficiencies

Partial combined immunodeficiency syndromes: Children with partial combined immunodeficiencies have

increased susceptibility to recurrent sinopulmonary infections

Children afflicted with Wiskott-Aldrich syndrome and ataxia-telangiectasia have the highest malignancy rates of all primary Immunodeficiencies

Patients with ataxia-telangiectasia are highly susceptible to radiation-induced malignancies and use of ionizing radiation for evaluation of these children should beperformed judiciously

Primary immunodeficiencies

Disorders of phagocytic cells and adhesion molecules:

Chronic granulomatous disease is the most common phagocytic disorder, occurring in approximately 1 in 125,000 live births

this disorder is seen most commonly in males

These children develop recurrent infections, commonly with catalase-positive bacteria, such as Staphylococcus aureus or fungi including Aspergillus, caused by defective intra-cellular killing by neutrophils .

This disease usually presents before 1 year of age with pulmonary infections occurring most frequently

Primary immunodeficiencies

Disorders of phagocytic cells and adhesion molecules: Chest radiographs or chest CT typically demonstrate

lymphadenopathy, recurrent pneumonia, and pleural thickening .

The radiographic manifestations of Aspergillus vary but segmental or lobar infiltrates, nodular opacities, and cavitation are typical .

Recurrent pneumonias and pulmonary abscesses are common

Other thoracic manifestations include lymphadenitis, osteomyelitis, and chest wall abscesses

Secondary immunodeficiencies:AIDS : Most of these cases are acquired through vertical

transmission from HIV-positive mothers

Pulmonary infections are a major source of morbidity and mortality in children with AIDS.

Fifty percent of children who die from AIDS do so as a result of complications from pulmonary disease

These children are at risk for many opportunistic infections, such as P carinii pneumonia (PCP) and mycobacterial pneumonia, acute bacterial pneumonias are common

Secondary immunodeficiencies:AIDS : The typical radiographic appearance of PCP includes

increased interstitial markings, which spread from an initial perihilar distribution to the periphery. Alveolar opacities often accompany progression of interstitial disease

Adenopathy and pleural effusions are rarely seen in association with PCP

Chest CT in children with PCP typically demonstrates peribronchial cuffing, patchy consolidation, ground glass opacity and parenchymal cysts

Secondary immunodeficiencies:AIDS : Children with AIDS are also susceptible to

mycobacterial infections, although the incidence is less common than in the adult population with AIDS.

The radiographic appearance mimics that seen in immunocompetent children with hilar adenopathy and lobar collapse or consolidation

Miliary tuberculosis in children with AIDS, however, is distinctly unusual

Secondary immunodeficiencies:Bone marrow and stem cell transplantation : The temporal sequence of events after BMT is predictable

with initial profound neutropenia lasting from 2 to 4 weeks

Local lung defense mechanisms are also impaired after BMT for up to 12 months

Early infectious complications after BMT are most frequently caused by bacteria and fungi, most commonly gram-negative organisms and Aspergillus

Chest radiographs may show a classic focal or lobar consolidation, although atypical features are not uncommon

Secondary immunodeficiencies:Bone marrow and stem cell

transplantation : Children are also at increased risk of viral infections,

most importantly respiratory syncytial virus, herpes simplex virus, adenovirus, and varicella

Radiographic findings are nonspecific but may include marked pulmonary hyperinflation and bilateral perihilar opacities, which coalesce into diffuse airspace disease

Fungal pneumonias in children who have undergone BMT are typically caused by Aspergillus or Candida species.

Secondary immunodeficiencies:Bone marrow and stem cell

transplantation : Angioinvasive pulmonary aspergillosis is reported to

occur in approximately 4% of children after BMT

Late sequellae of BMT differ from the complications encountered early in the posttransplant period and include infections and bronchiolitis obliterans, diffuse alveolar damage, lymphocytic interstitial pneumonitis, and relapse of the underlying disease

Secondary immunodeficiencies:Solid organ transplantation: The thorax is a common site of infectious complications to

the pediatric transplant recipient after solid organ transplantation

Long-term immunosuppressive therapy increases the risk of infection and the risk of neoplasms including various lymphoproliferative disorders

Children who have undergone renal transplantation are highly susceptible to infection with cytomegalovirus

P carinii pneumonia (PCP) and Aspergillus infection are also common infections after renal transplantation

Secondary immunodeficiencies:Patients with cancer: Children undergoing chemotherapy and radiation

therapy for malignancy are also at increased risk for pulmonary complications

Children who are predominately neutropenic as a result of chemotherapy are at risk for gram-negative infections, such as Pseudomonas aeruginosa and Klebsiella species, and gram-positive infections with such organisms as S aureus

Secondary immunodeficiencies:Patients with cancer: Children with leukemia are at increased risk for

infection with S pneumoniae, H influenzae, and gram-negative bacilli

Children with T-cell defects related to high-dose corticosteroid treatment or Hodgkin’s disease are more likely to develop viral or fungal infections

Conclusion:Combination of clinical knowledge and

radiological features is useful to understand the pathologic pulmonary changes encountered in the immunocompromised patients