[Histologic findings in the lung in sudden infant death]

Pneumonia due to viral and atypical organisms and their sequelae

Most children presenting with pneumonia in the industrialised world will have a viral or 'atypical' organism. The clinical features of these 'atypical' pneumonias may be indistinguishable from bacterial pneumonia. New diagnostic techniques such as the polymerase chain reaction may help in diagnosis and choice of treatment, where appropriate. The pathological and clinical features of infection with each agent are discussed, together with their sequelae.

Histomorphologic studies of the glottic region to elucidate the pathogenesis and functional significance of fibrinoid vocal cord lesions in infants and young children

Focal lesions of the vocal cord in form of fibrinoid necrosis and thickening of the basement membrane are morphological findings in infants and young children that receive only scant attention and are also controversially valued. We discuss two causes for the pathogenesis of these findings: (1) recurrent laryngospasms and (2) a laryngeal phonotrauma resulting from frequent spells of shrill, presumably high-frequency crying. The aim of our study therefore was to gain insight into the development and functional significance of these lesions by examining their histological patterns and to draw the pertinent conclusions. In 56 deaths (natural and unnatural causes, fetal life up to 4 years, no pathological or traumatic laryngeal lesions) histological investigations were carried out on putrefaction-free material. For the histomorphological studies, horizontal sections through the region of the vocal cord were obtained and stained according to conventional and immunohistochemical staining methods. In 42 cases the thickness of the basement membrane was determined morphometrically. In 12 of the 56 cases (21%) we observed staged variations of focal lesions, ranging from fibrinoid necrosis to degenerative lesions with pronounced macrophage involvement and deposits of PAS-positive plaques. Measurements at the basement membrane revealed a thickness of 7.9 microm. Separate measurements at the anterior and posterior portions of the vocal fold showed a ratio of 1.7:1. When the cases were subdivided into those with and without fibrinoid necrosis the ratios were 2.5:1 and 1.5:1. This different pattern makes it unlikely that laryngospasm is the sole or essential cause. Pathogenetically more important might be phonatory overstraining due to maximum vibrations in only the anterior portions of the vocal fold, which is not specific for later SIDS victims. This assumption is also supported by the often observed conspicuous phonetic behavior of some later SIDS victims and the absence of these stage-like vocal cord lesions in stillborns and adults. It is presumably an age-specific, temporary finding which is completely reversible.

Infections of the upper respiratory tract in cases of sudden infant death

The nasal cavities were examined in 56 cases of sudden infant death syndrome (SIDS) and 26 control cases and the following criteria were compared: inflammatory infiltration of the nasal mucosa (SIDS 59%--controls 65%; P = 0.577), diapedesis of inflammatory cells (SIDS 38%--controls 42%; P = 0.678), epithelial desquamation (SIDS 62%--controls 85%; P = 0.043); hyperemia (SIDS 66%--controls 65%; P = 0.951) and hypersecretion of the seromucous glands (SIDS 55%--controls 69%; P = 0.233). Only epithelial desquamation was found significantly more often in the controls than in SIDS cases, but these alterations are unspecific and are influenced by the postmortem interval. The intensity of rhinitis was not different between the SIDS and control groups. The frequency of rhinitis is therefore not specific for the sudden infant death syndrome, and seems to be merely a result of the high incidence of upper respiratory tract infections in this age group. We speculate, however, that infections of the nose in conjunction with other factors, such as prone position, covering of the head, hyperthermia, parental smoking and immaturity of the central nervous system, could play a role in the pathogenesis of the sudden infant death syndrome.

The potential role of bacterial toxins in sudden infant death syndrome (SIDS)

Toxigenic bacteria have been implicated in some cases of Sudden Infant Death Syndrome (SIDS). Although there is not much evidence that Clostridia spp. are associated with SIDS in Britain, strains of Staphylococcus aureus producing pyrogenic toxins have been isolated from significant numbers of these infants at autopsy The pyrogenic toxins, produced by some strains of group A Streptococcus pyogenes as well as staphylococci, are powerful "superantigens" that have significant physiological effects including induction of fever > 38 degrees C. In this article, interactions between genetic and environmental factors that might enhance colonization of epithelial surfaces by toxigenic staphylococci are analyzed: infant's expression of Lewis(a) antigen which acts as a receptor for some microorganisms; viral infections; the effect of mother's smoking on susceptibility to respiratory infection. Based on epidemiological findings and laboratory investigations, a hypothesis is proposed to explain how bacteria producing pyrogenic toxins might contribute to some cot deaths.

Possibility of separating toxins from bacteria associated with sudden infant death syndrome using anion exchange chromatography

AIMS

To develop techniques for the characterisation of toxins elaborated by a strain of Escherichia coli associated with sudden infant death syndrome (SIDS).

METHODS

E coli SIDS 04, isolated from the nasopharynx of a case of SIDS, was studied. Cell-free toxin preparations were standardised, their protein measured, and analytical separation of proteins achieved using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). Acetone precipitation of proteins was required prior to Coomassie blue staining of bands. Preparative separation was achieved on an anion exchange column using a programmed concentration gradient of NaCl in TRIS buffer. Fractions were tested individually or pooled for presence of lethal toxin including endotoxin. Lethal toxin was detected with the chick embryo test system. Endotoxin was measured using a chromogenic modification of the Limulus amoebocyte assay.

RESULTS

Twenty one peaks were detected by chromatography. Ten individual, or pooled, fractions were assayed for endotoxin which ranged from 27-33 pg/ml. Much greater variation was found when the same fractions were assayed in chick embryos. E coli fractions varied considerably in lethal toxicity, from 0/10 to 10/10 chick embryos killed/tested. Certain E coli fractions tested individually (lethality four out of 10 to eight out of 10) proved more lethal (10 out of 10) if pooled prior to testing.

CONCLUSIONS

In E coli infection associated with SIDS relatively low concentrations of extracellular protein are lethally toxigenic for the chick embryo model of SIDS. These proteins can be separated analytically by SDS-PAGE and preparatively by anion exchange chromatography. Toxicity of individual fractions is not correlated with endotoxin concentrations in samples tested.