Ultrastructure of Lamellar Bodies in Congenital Surfactant Deficiency

Congenital surfactant deficiency (CSD) is a newly identified neonatal lung disorder associated with a variety of molecular defects affecting surfactant synthesis and secretion in alveolar type II cells. The authors present ultrastructural findings of abnormal lamellar bodies in lung biopsies from 4 infants with CSD. All were term infants presenting shortly after birth with severe respiratory failure that was unresponsive to conventional therapy and all died within the first month of life. Lung biopsies were performed between 8 and 25 days of age. Biochemical and molecular studies in 2 unrelated male infants identified SP-B deficiency, one case with 121 ins 2 mutation and the second with a 209 + 4 A > G mutation. Light microscopy in both cases showed features of alveolar proteinosis. Ultrastructurally, alveolar type II cells lacked mature lamellar bodies, and their cytoplasm contained numerous pleomorphic inclusions with membranous and vesicular structures not seen in normal type II cells. The other 2 infants were a pair of siblings in whom molecular studies identified mutations in ABCA3 transporter gene. Light microscopy showed features of acinar dysplasia and desquamative interstitial pneumonitis. TEM studies revealed absence of mature lamellar bodies in type II cells and instead showed a mixture of cytoplasmic electron-dense inclusions with concentric membranes and distinctive electron dense aggregates. The ultrastructural changes in alveolar type II cells correlated well with specific gene defect. In SP-B deficiency, the absence of mature lamellar bodies is consistent with the postulated role for this protein in the formation of lamellar bodies. The lack of mature lamellar bodies in the ABCA3 gene mutations is due to the dysfunction of this endogenous lipid transporter that targets surfactant lipid moieties to the lamellar bodies. The findings demonstrate the importance of TEM studies of lung biopsies from infants with CSD as it is a critical adjunct in the diagnosis of neonatal lung disease and in defining the underlying cellular defects.

Prognostic value of placental ultrasound in pregnancies complicated by absent end-diastolic flow velocity in the umbilical arteries

Our objective was to evaluate the utility of gray-scale placental ultrasound for the detection of pathological lesions in the placentas of preterm pregnancies with abnormal fetoplacental blood flow (defined by absent or reversed end-diastolic flow velocities [ARED] in the umbilical arteries) before 32 weeks of gestation. Sixty consecutive structurally and chromosomally normal singleton pregnancies were evaluated. Pre-defined criteria were used to describe placental appearances using gray-scale real-time ultrasound. Proximal uterine artery Doppler waveforms were recorded using pulsed and color Doppler ultrasound. Each patient had a thrombophilia profile. Following delivery, a single perinatal pathologist reviewed each placenta at a gross and microscopic level blinded to the placental ultrasound findings. Placental shape or texture was abnormal on gray-scale ultrasound in 43/59 (73%) and echogenic cystic lesions (ECL) were found in 16 (27%). Uterine artery Doppler was abnormal in 47/60 (78%) cases. Thirty-eight pregnancies were subsequently delivered by planned Caesarean section in the fetal and/or maternal interest (birthweights 540-2300 g, mean gestational age 30.6 weeks) and 21 pregnancies resulted in the vaginal delivery of a stillborn fetus where fetal weight and/or gestational age did not justify Caesarean section (birthweights 85-600 g, mean gestational age 24.9 weeks). ECL had a low positive predictive value for both villous infarcts (63%) and for focal/massive perivillous fibrin deposition (40%). Nevertheless, the combination of abnormal uterine artery Doppler and abnormal gray-scale findings (abnormal placental morphology or ECL) was strongly predictive of stillbirth (17/21; sensitivity 81%, PPV 52%, p = 0.006 Fisher's exact test). Pregnancies with ARED in the umbilical arteries have a high perinatal mortality associated with pathology of the placental villi. Ultrasound examination of the placenta and its maternal blood supply may contribute to the perinatal management of these pregnancies.

Ultrasound diagnosis of severe thrombotic placental damage in the second trimester: an observational study

OBJECTIVES

To screen women with uteroplacental insufficiency between 18 and 26 weeks' gestation for sonographic evidence of destructive placental lesions, to observe the effect of low molecular-weight heparin (LMWH) in these cases, and to compare the outcome with similar but untreated controls.

METHODS

We screened 180 women at high risk for placental damage using 16-week maternal serum screening (alpha-fetoprotein and human chorionic gonadotropin), placental shape and texture, and uterine artery Doppler waveforms at the 18-20-week level II examination. Serial gray-scale examinations of placental texture were performed at 22, 24 and 26 weeks. LMWH was offered to women with ultrasound evidence of destructive placental lesions in the absence of intrauterine growth restriction and/or pre-eclampsia.

RESULTS

We prospectively identified six women (3.3%) with abnormal maternal serum screening and uterine artery Doppler in whom abnormal placental texture (echogenic cystic lesions) suggestive of destructive lesions in the placental parenchyma was found either at the 18-20-week ultrasound examination (n = 4), or by 26 weeks of gestation (n = 2). All six received LMWH and had live births (gestational age at delivery, 33-37 weeks; birth weight, 1000-3200 g). A further 14 women were referred with similar multiparameter evidence of placental damage at or after 26 weeks, outside the screening study. All had significant fetal growth restriction and were therefore not offered heparin. In 9/14 cases there was a perinatal death. Ischemic and/or thrombotic placental pathology was confirmed in each case, but no maternal thrombophilia disorders were identified in the 20 women.

CONCLUSIONS

Integrated biochemical and ultrasound testing of placental function at 16-20 weeks of gestation, followed by serial placental gray-scale ultrasound, may be an effective method of identifying a subset of pregnancies at high risk of adverse pregnancy outcome due to destructive lesions in the placental parenchyma. This strategy of identifying thrombo-occlusive placental lesions before the development of pregnancy complications may prove useful in the design of trials to study the effectiveness of LMWH in the prevention of clinical complications resulting from thrombo-occlusive placental disease.