Novel mutations in abetalipoproteinaemia and homozygous familial hypobetalipoproteinaemia

Abetalipoproteinaemia (ABL) and homozygous familial hypobetalipoproteinaemia (FHBL) are rare inherited disorders associated with low or undetectable levels of apolipoprotein B (apoB)-containing lipoproteins. Patients present with the symptoms and sequelae of fat malabsorption, including fat-soluble vitamin deficiencies. We describe two novel mutations: one an APOB gene mutation causing FHBL and the other a microsomal triglyceride transfer protein (MTP) gene mutation causing ABL. Two siblings of consanguineous parents were homozygous for an apoB mutation 4339delT causing an apoB-30.9 truncation. In another family, a boy born to consanguineous parents was homozygous for a 319 bp in-frame deletion of MTP exon 15 (c.2076-39_2303 + 52del319). All three children presented with malabsorption and liver dysfunction and had similar very low serum lipid, apoB, and fat-soluble vitamin levels. The FHBL parents had low serum lipid and apoB profiles distinguishing the disorder from the normal levels in ABL parents. Future patients presenting with FHBL or ABL should be genotyped to provide further insight into the varying clinical severity related to molecular heterogenicity in these two conditions.

Newborn screening for congenital hypothyroidism, Victoria, Australia, 1977-1997. Part 2: Treatment, progress and outcome

A controlled longitudinal prospective study is reported of physical and neuropsychological progress up to 12 years in 152 children with congenital hypothyroidism (CH), detected by newborn screening in the Australian state of Victoria and born between the onset of screening in mid-1977 and December 1988. Linear growth of the CH children was normal. Throughout they were slightly heavier and the median head circumference was slightly larger compared with reference data. Those with thyroid aplasia required a marginally larger dose of thyroxine to achieve euthyroidism. Assessment of cognitive outcome in the children with permanent primary CH revealed the mean scores at 2, 5 and 8 years to be from 8.5 (p<0.001) to 10.2 (p<0.001) points lower than in a group of 60 euthyroid controls. However, there was large overlap and, of the affected children, only 10.1% at 2 years, 3.9% at 5 years and 6.8% at 8 years fell more than 2 SD below the means of the euthyroid controls. On univariate analysis, variables shown to have significant correlation with cognitive outcome at 8 years in the CH children were newborn activity, baseline TT4 and FTI, initial T4 dosage, socio-economic classification, maternal age, maternal education and presence of a serious accompanying disorder. On multiple regression analysis, significant variables were baseline bone age, maternal age and education, and presence of a serious accompanying disorder. No single thyroidal or extra-thyroidal variable could be identified to account for the discrepancy between the children with CH and the controls.

Newborn screening for congenital hypothyroidism, Victoria, Australia, 1977-1997. Part 1: The screening programme, demography, baseline perinatal data and diagnostic classification

Clinical, demographic and laboratory data from infants with congenital hypothyroidism (CH) born in the Australian state of Victoria from the commencement of neonatal screening in mid-1977 until December 1988 are reported. These provide a baseline for a 12-year prospective longitudinal study on physical and neuro-psychological outcome until mid-1997, the subject of a second paper. Infants with CH were detected using a primary TT4 screening test. Demographic data were collected prospectively using a clinical assessment protocol. Nearly all affected infants underwent 99mTc pertechnetate scanning at the initial assessment to determine the underlying aetiology of their hypothyroidism. 704,723 infants were screened and 199 with permanent primary hypothyroidism (one in 3,541) were identified. The most common aetiologies were thyroid ectopia (46%), thyroid aplasia (33%), and 'dyshormonogenesis' (11%). The clinical abnormalities classically described in CH were more evident in infants with aplasia, and the striking female preponderance in infants with thyroid dysplasia (syn. dysgenesis) was confirmed. Other features included increased frequencies of 'dyshormonogenesis' in infants of parents of Middle-Eastern origin and of labour induction in infants with dysplasia. A closed posterior fontanelle was not found in any infant with thyroid aplasia.

Transient hyperphosphatasaemia: an important condition to recognize

OBJECTIVE

To investigate the prevalence and aetiology of transient hyperphosphatasaemia (TH) of infancy and childhood in a tertiary referral paediatric hospital.

METHODOLOGY

Retrospective review of the medical records of patients with measured plasma alkaline phosphatase (ALP) activity of over 1000 U/L.

RESULTS

Over a period of 1 year, 68 children with plasma ALP activity of over 1000 U/L were identified. The main aetiologies were liver disease (34 cases), TH (21 cases) and bone disease (11 cases). The mean age of children with TH was 1 year and 5 months and there was a male predominance (3:1). The children with liver and bone disease were older (mean ages of 6 years, 6 months and 5 years, 1 month, respectively) and there was no gender difference. The mean plasma ALP activity for the children with TH was 3395 U/L, and in those patients in whom ALP activity was measured sequentially, mean ALP returned to within normal limits after an average of 70 days. There was a seasonal predominance of TH cases, with a significant number presenting during the winter, suggesting a viral aetiology. The most common clinical presentation of children with TH was gastroenteritis (8/21).

CONCLUSION

Cases of TH can be clearly identified by considering the age of the patient and by excluding other known causes of markedly elevated ALP, in particular liver or bone disease. Using these exclusion criteria, the prevalence of TH was found to be high. Early recognition of this benign condition may prevent misdiagnosis and further unnecessary investigations.

Initial characterization of the GH-IGF axis and nutritional status of the Ati Negritos of the Philippines

BACKGROUND AND OBJECTIVE

The Ati Negritos are a Pygmy-like aboriginal population from the Philippines with physical characteristics of short stature, dark skin and woolly, kinked hair. Their final height, components of their GH-IGF axis and various nutritional markers are described. SUBJECTS, DESIGN AND MEASUREMENTS: Auxological data and sera for the components of the GH-IGF axis and nutritional parameters were collected from 9 adult Ati Negritos in their native environment and 10 Filipinos in Sydney.

RESULTS

The height SDS (- 3.66 +/- 1.1 vs. - 1.01 +/- 1.2), weight SDS (- 2.30 +/- 1.6 vs. 0.10 +/- 0.7), and BMI SDS (- 1.4 +/- 1.8 vs. - 0.2 +/- 0.5) between the two groups were significantly different (P < 0.01). The mean height of the 6 male Ati Negritos was 149 +/- 7 and 144 +/- 3 cm for the females and are comparable with the African Pygmies and the Mountain Ok people of Papua New Guinea. The Ati Negritos showed lower growth hormone binding protein (GHBP), insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein 3 (IGFBP-3), acid labile subunit (ALS), zinc, albumin, ferritin, iron, iron saturation and much higher insulin-like growth factor binding protein 2 (IGFBP-2) and plasma transferrin concentrations. No differences were noted in random growth hormone (GH), plasma insulin-like growth factor II (IGF-II), nor in their plasma concentrations of prealbumin, thyroid stimulating hormone (TSH) and free thyroxine (T4).

CONCLUSION

Perturbations of both the GH-IGF-I axis and nutritional markers exist in the Ati Negritos. These findings may be determinants of their stature; however, the aetiology of these changes remains to be fully elucidated.

Flow cytometric evaluation of defects of the mitochondrial respiratory chain

Cultured human skin fibroblasts from 12 patients with a variety of mitochondrial respiratory chain defects were examined for their capacity to oxidize dihydrorhodamine-123 to the fluorescent molecule rhodamine-123 using a flow cytometer. We found that cells from patients with functional defects in respiratory chain enzymes were less able to oxidize dihydrorhodamine-123 than those of healthy controls. Ten of the cell strains had reduced activity in at least one of the respiratory chain complexes and also showed significantly reduced fluorescence when compared to the mean of eight normal control cell strains. One patient had mitochondrial encephalomyopathy, lactic acidosis, and strokelike episodes (with the A3243G mutation) and reduced respiratory chain activities in muscle and liver. Molecular analysis did not show the mutation in cultured skin fibroblasts, and had correspondingly normal fluorescence. The 12th cell strain showed reduced fluorescence but did not reach statistical significance. This strategy could be of use in helping direct further investigations in patients, and in studying the biochemical pathogenesis of mitochondrial DNA mutations in cybrid studies.

Automated quantitation of total protein in cultured skin fibroblasts

An automated Coomassie Blue method of measuring total protein in cultured skin fibroblasts using a random access analyzer, the Roche MIRA, was compared to a manual dye binding method using bicinchoninic acid. The automated Coomassie Blue method is in common use in many routine laboratories for measurement of total protein in urine and CSF, and was found by us to be significantly faster than a manual protein method, with an average assay time of 2 min per sample. In addition, intra- and inter-run precision were comparable for the automated and manual methods, and compared favourable with other automated methods. We recommend that where the MIRA apparatus is available, consideration be given to its use for protein quantitation of cell or tissue extracts.

The association of thyroid dyshormonogenesis and deafness (Pendred syndrome): experience of the Victorian Neonatal Thyroid Screening Programme

Between 1977 and 1989, the Victorian Neonatal Thyroid Screening Programme detected five subjects with thyroid dyshormonogenesis and sensorineural deafness. These patients have been diagnosed as having Pendred syndrome. In two of the children, thyroid function tests which were initially abnormal at birth returned to normal spontaneously without treatment. However, hypothyroidism subsequently recurred and the children required thyroxine therapy. These two children could have been mistakenly diagnosed as having transient hypothyroidism. The detection of five patients with Pendred syndrome illustrates the importance of audiological assessment in all babies with thyroid dyshormonogenesis in whom there is increased uptake of isotope on thyroid scanning. In our experience, hearing loss in patients with Pendred syndrome may be progressive over time, so that repeated audiological assessments are necessary.

A review of therapeutic monitoring of chloramphenicol in patients with Haemophilus influenzae meningitis

Two hundred and seventy-seven serum chloramphenicol concentrations in 90 patients with Haemophilus influenzae type b meningitis were analysed retrospectively. Most patients were given chloramphenicol 25 mg/kg 6 hourly initially. Chloramphenicol concentrations were categorized as pre-dose ('trough') or post-dose ('peak'). Twenty-six per cent of the results were in the potentially toxic range (above 30 mg/L), and 18% were below 10 mg/L. Analysis of 46 pre- and post-dose measurements showed that for the intravenous (i.v.) route of administration, 23% of the pre-dose concentrations were higher than the corresponding post-dose levels and, for the oral route, 42% of the pre-dose levels were higher. Multivariate analysis of covariance demonstrated that chloramphenicol concentrations decreased significantly with increasing number of days of treatment and that the decline was steeper with i.v. administration. The results of this study emphasize the need for therapeutic monitoring of chloramphenicol concentrations, and suggest that chloramphenicol should be given as a loading dose of 40 mg/kg, followed by 25 mg/kg per dose 8 hourly for 3-4 days and then 6 hourly.

Transient primary hypothyroidism in the newborn: experience of the Victorian Neonatal Thyroid Screening Programme

Between May 1977 and December 1986, the Victorian Thyroid Screening Programme tested approximately 570,000 newborns for congenital hypothyroidism. One hundred and sixty-six cases of primary hypothyroidism, confirmed by formal thyroid function tests, were identified, of which 24 were later found to be transient. In addition, there were two patients with permanent dyshormonogenesis who passed through a stage of being biochemically euthyroid and so could have been diagnosed mistakenly as transient hypothyroidism. Fourteen of the transient cases were due to excessive intake of iodine. In two, this was due to maternal ingestion of iodide during pregnancy and in 12 the babies received large amounts of topical iodine antiseptic. Two cases were caused by maternal anti-thyroid antibodies and in eight instances the cause was unknown. The large number of cases due to the topical application of iodine antiseptic emphasizes the need for caution when using this substance in neonates.

Factitious hyponatremia in a patient with cholestatic jaundice following bone marrow transplantation

We report a case of factitious hyponatremia in a boy who had received a bone marrow transplant for acute myeloid leukemia. Following transplantation, he developed graft-versus-host disease and obstructive jaundice. The pseudohyponatremia was found to be due to hyperlipidemia, but there were some unusual features. The patient's plasma triglyceride concentration was not significantly raised, but he had an extremely elevated cholesterol concentration, probably due to the presence of lipoprotein-X. His plasma, when first separated at room temperature, was icteric and relatively clear but developed a dense turbidity on being frozen at -20 degrees C.

Screening for alcohol intoxication by the osmolar gap

Significant ethanol intoxication can be detected by measuring a large osmolar gap, i.e. a large difference between the measured and calculated plasma osmolality. In our laboratory, measurement of the osmolar gap with the application of a correction factor has been used as a screening test for alcohol intoxication and has been shown to be rapid and effective and to compare favourably with an accepted method for assaying ethanol (alcohol dehydrogenase). In only a few clinical situations is a more specific and accurate assay for ethanol required. In interpreting the result, it must be stressed that substances other than ethanol may occasionally cause a raised osmolar gap.

Should we follow up children with Henoch-Schönlein syndrome?

We reviewed 31 children who had had Henoch-Schönlein syndrome without nephritis at least 5 years before. None was found to have progressive renal disease and these patients do not require the same long-term follow-up as those with clinical renal involvement.