'Malignant Phenylketonuria' (PKU) Due to Dihydropteridine Reductase (DHPR) Deficiency.

DHPR deficiency is a rare autosomal recessively inherited metabolic disorder of tetrahydrobiopterin (BH4) regeneration. Clinical symptoms may comprise microcephaly, developmental delay, ataxia and seizures. BH4 is the cofactor for the enzyme phenylalanine (Phe)hydroxylase (PAH), and for tryptophan and tyrosine hydroxylases, both of which are essential for serotonin and dopamine biosynthesis. We present four patients in two families who are being treated at the National Centre for Inherited Metabolic Disorders (NCIMD). All are members of the Irish Traveller population. We have identified a homozygous mutation, c.353C>T, in the DHPR (QDPR) gene which, to the best of our knowledge, has not been previously described. The mainstay of treatment is a life-long Phe-restricted diet together with supplementation of L-dopa and 5-hydroxy tryptophan (5-HT) and folinic acid. In Ireland, there is neurological comorbidity in our adult DHPR patients, although the overall outcome is satisfactory and one affected female has three healthy children.

Lack of awareness of risk factors for primary toxoplasmosis in pregnancy.

BACKGROUND: The overall seroprevalence of toxoplasma antibodies in women of childbearing age in Ireland is 25% [1]. Hence, 75% of women remain susceptible to primary toxoplasma infection during pregnancy, which if transmitted to the foetus can cause ocular, neurological and other sequelae. Toxoplasma exposure during pregnancy can be avoided if there is an awareness of the potential sources of infection, mainly contaminated food, water, soil and cat faeces. AIMS: To determine risk factor exposure in a cohort of women with congenitally infected infants and to assess maternal risk awareness prior to diagnosis of infection. METHODS: Data, prospectively gathered during 2 years of pilot newborn screening for congenital toxoplasmosis in Ireland, was retrospectively analysed. Known risk factors for acquisition of infection were identified. Women were questioned regarding risk awareness and implementation of avoidance measures, if any, during pregnancy. RESULTS: Fifteen congenitally infected infants were identified by newborn screening. Seventy-three percent of their mothers (11/15) reported lack of knowledge concerning risk factors for toxoplasma infection or its potential threat to the foetus. Ingestion of raw or undercooked meat during pregnancy was the predominant source of toxoplasma cyst exposure identified. Contact with cats was reported in just one case. CONCLUSIONS: Most women were uneducated about the risks posed by Toxoplasma gondii exposure during pregnancy. There is a clear need for better educational programmes regarding primary prevention of congenital toxoplasmosis if neonatal infection is to be avoided.

Factor V Leiden (Arg506Gln), a confounding genetic risk factor but not mandatory for the occurrence of venous thromboembolism in homozygotes and obligate heterozygotes for cystathionine beta-synthase deficiency.

Thrombosis is the major cause of morbidity and mortality in individuals with untreated classical homocystinuria (HCU) due to cystathionine beta-synthase deficiency and characterised by severe hyperhomocysteinaemia. In addition, mild and moderate hyperhomocysteinaemia and Factor V Leiden (FVL; Arg506Gln) have recently been identified as thrombotic risk factors. FVL. which renders resistance to activated Protein C, is the most common inherited genetic risk factor for thrombosis with a high allelic frequency amongst Caucasians. As thrombophilia is a multigenic disorder, 26 individuals with HCU (median age 17.6 years, range 3.5-32.8 years) and 36 obligate heterozygotes (median age 51.5 years, range 34-74 years) were screened for FVL. All the HCU individuals received treatment, except one, within 6 weeks of birth for those who were diagnosed at birth through the national newborn screening programme (n = 20) and at the time of diagnosis for those late detected (n = 5, mean age of starting treatment 4.9 years, range 1.4-11 years). All had been free from venous thrombosis, except one HCU individual and one HCU obligate heterozygote. Neither of the two individuals with venous thrombosis carried FVL. Two independent individuals with HCU (male 14.8 years; female 18.2 years) were heterozygous for FVL (allelic frequency 3.8%) and three independent HCU obligate heterozygotes (males 40 and 45.8 years; female 45.6 years) were also heterozygous for FVL (allelic frequency 4.16%). The findings in this small group suggest that FVL is not a mandatory but a significant confounding risk factor for the occurrence of thrombosis in HCU individuals and additional contributing factors may be required for thrombosis to occur in HCU obligate heterozygotes with FVL heterozygosity. Our data also suggest that treatment of HCU not only reduces the thrombotic risk in patients with isolated HCU but also in those with the additional FVL heterozygosity.

Newborn screening for homocystinuria: Irish and world experience.

Newborn screening for cystathionine beta-synthase deficiency (homocystinuria; HCU) was started in the late 1960s using a bacterial inhibition assay (BIA). At least seven countries have either national or regional screening programmes; 12 programmes are known to have discontinued. The worldwide incidence of HCU is approximately 1 in 335,000 but varies from 1:65,000 (Ireland) to 1:900,000 (Japan). Methodologies include the BIA, one-dimensional or thin-layer amino acid chromatography and, more recently, tandem mass spectrometry. The BIA diagnostic cut off concentration of blood methionine varies from 67 to 270 micromol/ (10-40 mg/l) with a median of 135 micromol/l (20 mg/l). In Ireland, 25 cases of HCU from 19 families have been identified from 1.58 million newborn infants since 1971; 21 cases were detected through the screening programme. Of the four missed cases, three were breast-fed at the time of blood collection and one was pyridoxine responsive. These findings were in broad agreement with the results from five other programmes, in which approximately one in every five cases was missed by the screening programme. Early hospital discharge, low protein intake, high blood methionine cut-off concentration and pyridoxine responsiveness were all identified as contributing to missed cases.

Cholesterol-lowering drug therapy in a patient with receptor-negative homozygous familial hypercholesterolaemia.

Familial hypercholesterolaemia (FH) is caused by mutations in the gene for the low density lipoprotein (LDL) receptor. It is generally believed that homozygous FH patients do not respond well to lipid-lowering drug therapy with inhibitors of 3-hydroxy-3-methylglutaryl CoA reductase because they cannot respond to an increased demand for hepatic cholesterol by up-regulation of LDL-receptor activity. In this paper we show that serum cholesterol in a homozygous FH patient with a receptor-negative LDL-receptor phenotype was reduced by 30% after treatment with simvastatin alone and by a further 11% with simvastatin in combination with probucol and nicotinic acid. The patient was a true homozygote, with two identical alleles of the LDL receptor gene in which a previously undescribed point mutation in exon 11 introduces a premature termination codon at residue 540 in the protein; the mutant protein is predicted to be truncated in the domain with homology to the epidermal growth factor precursor. Cultured cells from the patient were unable to bind, internalise or degrade LDL by the receptor pathway and there was no immunodetectable LDL receptor protein in the cells. Thus the lipid lowering effect of simvastatin in this individual must involve mechanisms other than stimulation of LDL receptors.

Identification of bone and liver metastases from breast cancer by measurement of plasma alkaline phosphatase isoenzyme activity.

Plasma alkaline phosphatase isoenzyme activities were determined in patients with breast cancer to diagnose and monitor bone and liver metastases. Bone alkaline phosphatase activity was increased in 21 of 50 patients (42%) with radiologically confirmed bone metastases, while total alkaline phosphatase activity was increased in only 10 of 50 (20%); liver alkaline phosphatase activity was raised in 12 of 25 patients (48%) with liver metastases. All patients with liver metastases had bone metastases. Bone alkaline phosphatase activity was significantly higher in patients with symptomatic bone disease. Isoenzyme determination provided additional information that would have changed patient management in five of 20 patients who were monitored serially. Measurement of alkaline phosphatase isoenzyme activity, though less sensitive than imaging procedures, can assist in screening for, and in early detection of, a high proportion of bone and liver metastases, and can provide useful objective evidence of their response to treatment.

Heat treatment for endocrinological investigations on plasma positive for human immunodeficiency virus (HIV).

The effects of heat treatment of serum samples on the hormone analyses used in this laboratory were studied. Total T4, testosterone, progesterone, and growth hormone were not systematically affected by heat treatment over the whole range of analyte concentrations studied; for thyroid stimulating hormone, no effect was noted on serum samples with concentrations of less than 10 mU/l. Significant changes occurred in total T3, cortisol, follicle stimulating hormone, luteinizing hormone, and prolactin. It is suggested that with appropriate preliminary study, heat treated plasma samples may be used in endocrinological investigations without adversely affecting the diagnostic validity of the results.

Measurement of biliary alkaline phosphatase by mini-column chromatography and by electrophoresis and its application to the detection of liver metastases in patients with breast cancer.

We describe a simple, rapid, and reproducible ion exchange mini-column chromatographic method for the quantitative measurement of biliary alkaline phosphatase in plasma. We have used this method to evaluate a cellulose acetate electrophoretic method, which was used to assess the value of measuring biliary alkaline phosphatase in 85 patients with breast cancer investigated for possible hepatic metastases. Biliary alkaline phosphatase activity was abnormal in 19 of 24 patients (79%) with liver metastases, but abnormalities were also found in 12 of 61 patients (20%) without hepatic metastases; in only 37% of patients with positive test results was this a consequence of liver metastases. For the identification of liver metastases, therefore, the method has useful sensitivity but limited specificity. Neither sensitivity nor specificity was significantly better than that of plasma gamma-glutamyltransferase activity, which was measured concomitantly.