Pneumonia

Bacterial

Viral

Mycoplasma

Age

Any

Mainly less than 2 years old

3–15 years old

Season

Year-round

Winter

Spring

Presentation

Sudden

Variable

Insidious

Fever

High

Variable

Tachypnea

Common

Infrequent

Cough

Scarce

Frequent

Frequent and intense

Related symptoms

Chest pain

Acute rhinorrhea

Conjunctivitis

Exanthema

Arthralgias

Otalgia

Pulmonary examination

Condensation syndrome

Wheezing is frequently present

Condensation is sometimes present

Wheezing or condensation syndrome

Bronchial sounds, fine crackles

Bronchophony

Localized fine crackles

Table 32.2

Clinical manifestations of pneumonia caused by Mycoplasma

Very frequent	Frequent	Regular frequency	Infrequent
Cough	Headache	Myalgias	Conjunctivitis
			Odynophagia
Fever	Lack of energy	Wheezing	Skin rush
			Otalgia
	Expectoration		Vomiting
			Acute rhinitis
	Crackles		Adenopathy
			Pharyngitis

Extrapulmonary Manifestations

According to the subsets of patients studied, a variable percentage (10–20%) may have extrapulmonary compromise, which happens before, during, or after the pulmonary infection caused by MP, even when no symptoms are present. The most common ones are these:

Cutaneous

Present in 15–20% of the patients and are self-limited. Among them we have the following skin conditions: maculous eruptions, morbilliform rashes, papulovesicular rash, urticaria, erythema nodosum, erythema multiforme major (Steven–Johnson), and bullous.

Neurological

The first cause of extrapulmonary pathology. There have been cases of encephalitis, meningitis, aseptic meningoencephalitis, transverse myelitis, Guillain–Barré syndrome, peripheral neuropathy, cerebellar syndrome, and mental confusion. There is evidence that direct invasion and autoimmunity are the pathogenesis of neurological compromise.

1.

Hematological: Hemolytic anemia caused by cold agglutinins, autoimmune hemolysis, disseminated intravascular coagulation, thrombocytopenic purpura, and aplastic anemia.
2.

Articular: Mono- or polyarthritis (most frequent cause according to our experience in Chile).
3.

Cardiac: Myocarditis, pericarditis, arrhythmia, and heart failure.
4.

Renal: Acute nephritis, IgA nephropathy.
5.

Oculars: Conjunctivitis, anterior uveitis, iritis, hemorrhagic retinitis (very rare).

Radiology

The chest X-ray usually shows a segmented condensation that compromises the inferior lobes, in one or both sides, or the central perihilar regions. The usual image is nonhomogeneous, irregular, with interstitial or alveolar shadows, and sometimes atelectasis may be present. Sometimes the following can be observed: a lobar or multilobar condensation of a greater extension, small pleural effusions, diffuse or nodular interstitial infiltrations, hilar adenopathy, abscess, or peribronchovascular enlargements, which are rare (Figs. 32.1, 32.2, and 32.3). Our studies show interstitial images in 22.6% of patients, mixed in 28%, and alveolar in 48%; 10% presented with pleural compromise, and no chest tubes were needed for the pleura. Local experience suggests that 20% of the pulmonary images caused by MP are indistinguishable from those of classic pneumococcal pneumonia or of the CP chest X-ray pattern. X-ray findings may persist during 2 to 6 weeks, depending on how early the antibiotic treatment is prescribed.

../images/441522_1_En_32_Chapter/441522_1_En_32_Fig1_HTML.jpg — Fig. 32.1

Interstitial-alveolar pneumonia . Chest X-ray of 9-year-old schoolchild shows a right lower lobe interstitial-alveolar image

../images/441522_1_En_32_Chapter/441522_1_En_32_Fig2_HTML.jpg — Fig. 32.2

Alveolar pneumonia . Chest X-ray of 6-year-old schoolchild presenting with an extensive bilateral lobar consolidation (similar to that caused by *Streptococcus pneumoniae*)

../images/441522_1_En_32_Chapter/441522_1_En_32_Fig3_HTML.jpg — Fig. 32.3

Alveolar pneumonia and pleural effusion . Chest X-ray of 7-year-old schoolchild presenting with nasal bilateral condensation and left pleural effusion

Laboratory Diagnosis

Classic Diagnosis Techniques

Culture and serology using the complement fixation (FC) test have their limitations in clinical practice. Complex nutritional sources are required for isolation, and although the specificity of the procedure is total (100%), its sensitivity varies between 60% and 70%. MP grows slowly in culture media; it is a cumbersome microorganism, and visible colonies take from 2 to 6 weeks to appear. Consequently, most laboratories do not conduct this test. FC is a technique that measures a mixture of IgM and IgG. The antigens used are related to several microorganisms and tissues, which causes unspecific reactions and yields false-positives. Because there usually is a high IgG level in the population, caused by previous infections, this technique requires serum-matched samples to prove seroconversion.

Serological Diagnosis

IgM detection is the most common test ordered in general pediatrics to diagnose pneumonia caused by MP. Although its sensitivity depends on the humoral immune response and the time at which the test was taken, generally IgM appears somewhere between 7 to 10 days after the onset of the clinical condition, and it rapidly increases, which makes it a fundamental pillar in the diagnosis of the infection caused by this microorganism, with a sensitivity of 80% or more. Nevertheless, in some patients, especially those under 2 years old, the IgM does not develop until 2 weeks after the beginning of the disease, which limits the sensitivity of this diagnostic procedure. IFI to determine IgM considers as a positive a number of 1/32 titers, and it is a classic technique for the diagnosis, but its reading requires trained personnel. Enzyme immune assays (EIA) are techniques that are easy to implement in clinical laboratories and can detect IgM and IgG separately, which eases the differentiation between an active infection and a previous one. It has been proven that IgM in children can have sensitivity levels as high as 89% to 92%. Also, the specificity of IgM detection done through enzyme-linked immunosorbent assay (ELISA) can vary in about 25% to 90%, depending on the commercial kit being used.

DNA Amplification Polymerase Chain Reaction (PCR)

Nucleic acid amplification techniques have a great potential for MP diagnosis, because of their specificity and because they quickly deliver results. Also, they are the best diagnostic tool when treating immunocompromised children and infants who have not reached the first year of life. These patients have a lower humoral immune response when facing this agent. Nevertheless, the presence of MP in the upper respiratory tract may be an obstacle, particularly during epidemics. In Chile, it has been detected in 2% of healthy children. In children between 1 to 4 years of life, it was detected in 1.9%, and in children between the ages of 4 to 15 it appeared in 5% of cases. During the periods in which the incidence of MP is greater, the presence of MP also increases. A 15% increase in relationship to the MP presence has been observed in children who are in contact with family members who are undergoing respiratory infections caused by these bacteria. The new nucleic acid amplification techniques, such as the nucleic acid sequence-based amplification (NASBA) and conventional, nested, or real-time PCR (Fig. 32.4), are attractive alternatives when determining the diagnosis. For ARN, NASBA is intrinsically more sensitive than conventional amplification techniques, and further, NASBA can also measure the microbial load in the sample. PCR in real time can identify an active infection through the detection and quantification of the accumulation of amplified DNA as the reaction develops.

../images/441522_1_En_32_Chapter/441522_1_En_32_Fig4_HTML.jpg

Tags: Pediatric Respiratory Diseases A Comprehensive Textbook

Nov 7, 2020 | Posted by admin in Uncategorized | Comments Off

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