SLC26A2 disease spectrum in Sweden - high frequency of recessive multiple epiphyseal dysplasia (rMED)

Diastrophic dysplasia (DTD) is an autosomal recessive skeletal dysplasia caused by SLC26A2 mutations. Clinical features include short stature, joint contractures, spinal deformities, and cleft palate. SLC26A2 mutations also result in other skeletal dysplasias, including the milder recessive multiple epiphyseal dysplasia (rMED). DTD is overrepresented in Finland and we speculated that this may have influenced the prevalence and spectrum of SLC26A2-related skeletal conditions also in Sweden. We reviewed the patient registry at Department of Clinical Genetics, Karolinska University Hospital, Stockholm to identify subjects with SLC26A2 mutations. Seven patients from six families were identified; clinical data were available for six patients. All but one patient had one or two copies of the Finnish SLC26A2 founder mutation IVS1+2T>C. Arg279Trp mutation was present in compound heterozygous form in five patients with phenotypes consistent with rMED. Their heights ranged from -2.6 to -1.4 standard deviation units below normal mean and radiographic features included generalised epiphyseal dysplasia and double-layered patellae. Two rMED patients had hypoplastic C2 and cervical kyphosis, a severe manifestation previously described only in DTD. Our study confirms a high prevalence of rMED in Sweden and expands the phenotypic manifestations of rMED.

Growth charts for monitoring postnatal growth at NICU of extreme preterm-born infants

AIM

To provide growth charts for clinical monitoring of extra-uterine growth from birth to full-term age, in infants born before 26 weeks of gestation, hospitalized at neonatal intensive care unit (NICU), and compare it to the commonly used Swedish preterm birth-size reference.

METHODS

This retrospective longitudinal cohort comprised all infants born before 26 + 0 weeks of gestation and surviving to full-term age (n = 162), admitted to the NICU, Karolinska Hospital during the period January 1990 to December 2002. Body weight was recorded daily, head circumference (HC) weekly and length twice a month.

RESULTS

Birth weight (BW), length and HC showed a normal distribution without significant gender difference. The majority of the infants showed a pronounced postnatal growth restriction for all growth variables with increasing deviation from the reference with age. The mean initial weight loss was 16% with nadir at 6 days of age and a mean time to regain BW of 18 days. At discharge from NICU, 75% of those initially appropriate for gestational age infants were below -2 standard deviation scores for at least one of the body size variables.

CONCLUSION

The poor extra-uterine growth pattern points to the need of growth curves for extra-uterine growth of extremely premature infants.

Increased inspiratory effort in infants with a history of apparent life-threatening event

The objective of this study was to compare the results of polysomnography between infants with a history of apparent life-threatening event (ALTE) and controls. In this case-control study, 40 full-term ALTE infants, aged 2-36 wk at the time of the event, were compared with 40 age- and sex-matched randomly selected controls. SaO2, tcpO2, tcpCO2, heart rate (HR), vector of rib cage and abdominal respiratory movements (phase angle, as an index of inspiratory effort) were recorded during natural nocturnal active and quiet sleep (AS, QS). SaO2, tcpO2, tcpCO2 were similar in ALTE and controls in both sleep states. Phase angle was increased in ALTE infants in both AS (59+/-46 vs 26+/-17 degrees) and QS (53+/-46 vs 18+/-14, p < 0.001). Eleven ALTE infants (27.5%) experienced SaO2 < 90%, with a mean decrease in SaO2 to 86+/-1.6% (mean +/- SD), compared with 10% for controls (p=0.003). In eight ALTE infants, SaO2 values <90% were linked to thoracoabdominal asynchrony. SaO2 < 90% in conjunction with HR <100 bpm were detected in three ALTE infants and one control. Periodic breathing was observed in 45% of ALTE infants and 40% of controls.

CONCLUSION

The mean values of oxygen saturation, tcpO2 and carbon dioxide levels in ALTE infants are comparable with those of healthy controls but the ALTE infants exhibit more hypoxaemic episodes and increased inspiratory effort during sleep.

Breathing patterns, oxygen and carbon dioxide levels in sleeping healthy infants during the first nine months after birth

Data on arterial oxygen saturation (SaO2), transcutaneous PO2, pCO2 (tcpO2, tcpCO2) and breathing patterns in sleeping healthy term infants were obtained during the first 9 mo after birth. Forty-four healthy infants, mean GA at birth 40 +/- 1.0 wk, mean BW 3520 +/- 562 g were examined between 2 wk and 9 mo postnatally in a cross-sectional study. SaO2, tcpO2, tcpCO2, heart rate (HR), rib cage and abdominal respiratory movements were recorded during natural nocturnal sleep, stratified for sleep states (active sleep (AS), indeterminate sleep (IS), quiet sleep (QS)). The data on AS and IS were pooled as in previous studies. The variables were analysed with respect to age. SaO2 in AS + IS and QS was 96.1 +/- 1.3%, 96.6 +/- 1.4%, respectively. TcpO2 in AS + IS was 10.6 +/- 1.1 kPa and 10.7 +/- 1.3 kPa in QS, while tcpCO2 in AS + IS was 5.4 +/- 0.3 kPa and 5.4 +/- 0.4 kPa in QS. Neither SaO2 nor tcpO2 was influenced by age. TcpCO2 decreased significantly postnatally. Five infants (11.3%) experienced episodes of hypoxaemia with a mean decrease in SaO2 to 86 +/- 1.5%. In four infants these hypoxaemic episodes were linked to upper airway obstructions. Episodes of SaO2 < 90% in conjunction with a decrease in HR to < 100 bpm were detected in one infant only. Periodic breathing (PB) was observed in 38.6% of infants.

CONCLUSION

Oxygenation and carbon dioxide levels in sleeping healthy term infants were comparable to those reported in older children. Hypoxaemic episodes, if present, are associated with upper airway obstruction. PB, often assumed to be a pathological feature, is a normal breathing pattern in this age group.