A case of Wilson-Mikity syndrome with high serum KL-6 levels

Impact of chest radiography-based definition of bronchopulmonary dysplasia

BACKGROUND

Bubbly/cystic appearance on chest radiograph is an important factor in severe-type bronchopulmonary dysplasia (BPD) in Japan. The aim of this study was to determine the perinatal characteristics and neonatal complications of the bubbly/cystic(+) group in extremely preterm infants with BPD, that is, oxygen dependency at day 28 after birth (BPD28).

METHODS

This was a multicenter retrospective cohort study of population data from infants (birthweight, <1,500 g) enrolled in the Neonatal Research Network of Japan. Of the 15 480 infants born at <28 weeks' gestational age (GA) between 2003 and 2012, 8,979 met the BPD28 criteria. The BPD28 infants were classified according to bubbly/cystic appearance on radiograph (±) at >28 postnatal days.

RESULTS

The bubbly/cystic(+) group had lower GA and birthweight and required longer mechanical ventilation and oxygen dependency than the bubbly/cystic(-) group. After adjustment for confounding factors, bubbly/cystic appearance was an independent risk factor for home oxygen therapy at discharge.

CONCLUSION

Bubbly/cystic appearance on chest radiograph was a predictor of short-term respiratory outcomes in infants with BPD28, which is diagnosed much earlier (≥28 postnatal days), and has a potentially different etiology to BPD36 (oxygen and/or positive pressure respiratory support dependency at 36 weeks' postmenstrual age).

Bubbly and cystic appearance in chronic lung disease: Is this diagnosed as Wilson-Mikity syndrome?

Wilson-Mikity syndrome (WMS) was first reported in 1960 by Wilson and Mikity. They described preterm infants who developed areas of cystic emphysema in the first month of life with subsequent progression to chronic lung disease (CLD) of infancy, although these infants did not exhibit early respiratory distress, such as respiratory distress syndrome (RDS). This condition was widely accepted over the next 20 years, but WMS is now rarely mentioned and is commonly considered an anachronism. In Japan, CLD is classified into six types according to the presence of RDS and/or intrauterine inflammation and appearance on chest X-ray. One type of CLD (type III, which accounts for 13.5% of all CLD) is defined as history of intrauterine inflammation and the typical bubbly and cystic appearance on chest X-ray described in the original report of WMS. There is insufficient evidence to determine whether WMS exists or whether WMS is relatively common only in Japan and not in other countries. It is important, however, to distinguish this type of CLD from other types because the strategy for the prevention or treatment of CLD should be different according to its origin, cause, and risk factors.

Pulmonary Collectins in Diagnosis and Prevention of Lung Diseases

Pulmonary surfactant is a complex mixture of lipids and proteins, and is synthesized and secreted by alveolar type II epithelial cells and bronchiolar Clara cells. It acts to keep alveoli from collapsing during the expiratory phase of the respiratory cycle. After its secretion, lung surfactant forms a lattice structure on the alveolar surface, known as tubular myelin. Surfactant proteins (SP)-A, B, C and D make up to 10% of the total surfactant. SP-B and SPC are relatively small hydrophobic proteins, and are involved in the reduction of surface-tension at the air-liquid interface. SP-A and SP-D, on the other hand, are large oligomeric, hydrophilic proteins that belong to the collagenous Ca²⁺-dependent C-type lectin family (known as “Collectins”), and play an important role in host defense and in the recycling and transport of lung surfactant (Awasthi 2010) (Fig. 43.1). In particular, there is increasing evidence that surfactant-associated proteins A and -D (SP-A and SP-D, respectively) contribute to the host defense against inhaled microorganisms (see 10.1007/978-3-7091-1065_24 and 10.1007/978-3-7091-1065_25). Based on their ability to recognize pathogens and to regulate the host defense, SP-A and SP-D have been recently categorized as “Secretory Pathogen Recognition Receptors”. While SP-A and SP-D were first identified in the lung; the expression of these proteins has also been observed at other mucosal surfaces, such as lacrimal glands, gastrointestinal mucosa, genitourinary epithelium and periodontal surfaces. SP-A is the most prominent among four proteins in the pulmonary surfactant-system. The expression of SP-A is complexly regulated on the transcriptional and the chromosomal level. SP-A is a major player in the pulmonary cytokine-network and moreover has been described to act in the pulmonary host defense. This chapter gives an overview on the understanding of role of SP-A and SP-D in for human pulmonary disorders and points out the importance for pathology-orientated research to further elucidate the role of these molecules in adult lung diseases. As an outlook, it will become an issue of pulmonary pathology which might provide promising perspectives for applications in research, diagnosis and therapy (Awasthi 2010).

Wilson-Mikity syndrome: updated diagnostic criteria based on nine cases and a review of the literature

BACKGROUND

Nearly 50 years ago, Wilson and Mikity described a syndrome (WMS) of chronic lung disease (CLD) in premature infants, characterized by early development of cystic interstitial emphysema (PIE), despite minimal ventilatory support. The validity of the diagnosis is currently unclear; now considered either an anachronism, part of BPD spectrum or included within various poorly defined diagnoses such as chronic pulmonary insufficiency of prematurity (CPIP).

OBJECTIVES

To define clinically useful diagnostic criteria for WMS so its position in the spectrum of CLD of infancy can be established.

METHODS

We studied nine patients who fulfilled WMS criteria, combining this data with a detailed review of the available literature.

RESULTS

Despite minimal respiratory support at birth, all developed generalized or lobar cystic PIE by 3 weeks of age, followed by slow inflammatory progression over a further 2-3 months. Final outcome was variable but most were left with some degree of CLD.

CONCLUSIONS

WMS is a rare but clearly identifiable syndrome with significant morbidity, predominantly affecting infants below 1,500 g birth weight. The earliest pathology appears to be alveolar air leak. Inflammatory activation induced by cystic interstitial air may cause the subsequent progressive respiratory disease. Management is supportive but should include investigation for pulmonary hypertension.

Plasma KL-6 predicts the development and outcome of bronchopulmonary dysplasia

Circulating KL-6 is a specific indicator of pulmonary injury affecting the alveolar epithelium and interstitium. Our preliminary study suggested the usefulness of plasma KL-6 as a marker of bronchopulmonary dysplasia (BPD). To confirm the diagnostic value of KL-6 for BPD as well as to determine the reference range, we conducted a larger prospective study in 135 preterm infants <32 wk GA. Among the infants without oxygen dependence at a postconceptional age of 36 wk, the plasma KL-6 level showed no significant association with GA at any time. Among 42 infants <28 wk GA, plasma KL-6 levels were significantly higher in those with moderate/severe BPD compared with those with no/mild BPD. A plasma level of 199 U/mL at 1 wk or 232 U/mL at 2 wk was an excellent predictor of moderate/severe BPD <28 wk GA (positive predictive value of 83% and 80%, respectively). Unlike nonspecific markers of inflammation or fibrosis, KL-6 objectively reflects the severity of pulmonary injury irrespective of the treatment or the radiographic changes. Therefore, not only as a good marker, measurement of KL-6 may also help to provide new insights into the pathogenesis of BPD.