Summary. People with genetic haemochromatosis (GH) accumulate iron from excessive dietary absorption. In populations of northern European origin, over 90% of patients are homozygous for the C282Y mutation of the HFE gene. While about 1 in 200 people in the general population have this genotype the proportion who develop clinical haemochromatosis is not known. The influence of HFE genotype on iron status was investigated in 10 556 blood donors. The allele frequencies of the C282Y and H63D mutations were 8´23% and 15´3% respectively. Heterozygosity for C282Y occurred in 1 in 7´9 donors, for H63D in 1 in 4´2 donors, and 1 in 42 were compound heterozygotes. Homozygosity for H63D occurred in 1 in 42 donors and 1 in 147 (72) were homozygous for C282Y. Mean values increased for transferrin saturation (TS) and serum ferritin (sFn), and decreased for unsaturated iron binding capacity (UIBC) in the order: donors lacking the mutations, H63D heterozygotes, C282Y heterozygotes, H63D homozygotes, compound heterozygotes and C282Y homozygotes, but serum ferritin (sFn) concentrations were no higher in H63D heterozygotes and C282Y heterozygous women than in donors lacking mutations. The percentage of donors failing the screening test for anaemia or of those with sFn , 15 mg/l did not differ among the genotype groups. C282Y and H63D heterozygotes and donors homozygous for H63D were at no greater risk of iron accumulation than donors lacking mutations, of whom 1 in 1200 had both a raised TS and sFn. The risk was higher for compound heterozygotes (1 in 80, P 0´003) and for C282Y homozygotes (1 in 5, P , 0´0001). There was no correlation between sFn and either age or donation frequency in C282Y homozygotes. None of the 63 C282Y homozygous donors interviewed showed physical signs of overload or were aware of relatives with haemochromatosis. The Welsh Blood Service collects blood from about 140 000 people each year including an estimated 950 who are homozygous for HFE C282Y. They are probably healthy and unaware of any family history of iron overload.

The efficacy of prophylactic penicillin and of 14 valent pneumococcal vaccine in preventing pneumococcal infection in homozygous sickle cell (SS) disease was investigated in 242 children aged 6 months to 3 years at entry. In the first five years of the trial there were 11 pneumococcal infections in the pneumococcal vaccine treated group, 10 by serotypes present in the vaccine. Type 23 accounted for five of these, and there was evidence of higher infection rates in those given the vaccine before age 1. No pneumococcal isolations occurred in the penicillin group while receiving penicillin, although four isolations occurred within one year of stopping penicillin.Probably the most effective prophylaxis against pneumococcal infection requires penicillin beyond the age of 3. The age at which pneumococcal vaccine should be given must await further data on antibody response and clinical efficacy in these patients.

In northern Europe, about 90% of patients with hereditary haemochromatosis (HH) are homozygous for a single mutation (C282Y) of the HFEgene and approximately 1 in 150 people in the general population carries this genotype. However, the clinical significance of HFE mutations remains uncertain, as is the proportion of people homozygous for C282Y who will develop clinical symptoms leading to a diagnosis of HH. A systematic review of patients with HH over a 2-year period within a defined UK region has revealed that only 1.2% of adult C282Y homozygotes have been diagnosed with iron overload and received treatment. In those in whom body iron load could be estimated, only 51% has more than 4 g iron (the diagnostic threshold for iron overload).

Porphyria cutanea tarda is a skin disease caused by photosensitization by porphyrins whose accumulation is caused by deficiency of hepatic uroporphyrin- ogen decarboxylase activity. Mutations in the uroporphyrinogen decarboxylase gene are present in the low-penetrant, autosomal dominant familial form but not in the commoner sporadic form of porphyria cutanea tarda. We have investigated the relationship between age of onset of skin lesions and mutations (C282Y, H63D) in the hemochromatosis gene in familial (19 patients) and sporadic porphyria cutanea tarda (65 patients). Familial porphyria cutanea tarda was identified by mutational analysis of the uroporphyrinogen decarboxylase gene. Five previously described and eight novel mutations (A80S, R144P, L216Q, E218K, L282R, G303S, 402-403delGT, IVS2 + 2 delTAA) were identified. Homozygosity for the C282Y hemochromatosis mutation was associated with an earlier onset of skin lesions in both familial and sporadic porphyria cutanea tarda, the effect being more marked in familial porphyria cutanea tarda where anticipation was demonstrated in family studies. Analysis of the frequencies of hemochromatosis genotypes in each type of porphyria cutanea tarda indicated that C282Y homozygosity is an important susceptibility factor in both types but suggested that heterozygosity for this mutation has much less effect on the development of the disease.

Background and aims: Although most cases of hereditary haemochromatosis are associated with homozygosity for the C282Y mutation of the HFE gene, clinical penetrance varies and other genes may modify disease expression. If so, relatives from clinically affected families, by inheriting such genes, may accumulate more iron. To seek evidence for this, we compared iron status and morbidity in unselected first degree relatives of two groups of index cases from South Wales, namely asymptomatic C282Y homozygotes identified by genetic screening of blood donors (n = 56) and C282Y homozygous haemochromatosis patients presenting clinically (n = 60). Methods: All participating relatives had a structured interview, clinical assessment, and laboratory investigations. Health related quality of life was measured (SF-36 version 2). Results: In total, 92% of 180 eligible first degree relatives were interviewed in the ''screened'' family group and 85% of 143 eligible relatives in the ''patient'' group. Of 59 relatives homozygous for C282Y, 76% of men and 32% of women had the ''iron phenotype'' (raised transferrin saturation and serum ferritin). Logistic regression modelling of the iron phenotype risk showed that 42% of the initial model deviance could be explained by homozygosity for C282Y, another 6% by lifestyle factors, and 6% by being male. Family group membership was not a significant risk factor. Morbidity and SF-36 scores did not differ significantly either between C282Y homozygotes and relatives lacking C282Y, or between C282Y homozygotes from the ''screened'' and ''patient'' groups. Serious morbidity (including cirrhosis) was low in both groups of relatives. Conclusions: HFE C282Y homozygosity has a high penetrance for iron accumulation but a low clinical penetrance. Lack of excess morbidity among C282Y homozygous relatives of index cases who presented clinically suggests that residual unknown genetic or environmental factors do not greatly influence clinical outcome among C282Y homozygotes.

Summary.The recently described association between haemochromatosis and mutations in the HFE or HLA-'H' gene has prompted the need for a simple and rapid genetic test capable of detecting multiple mutations simultaneously. Heteroduplex analysis, a new diagnostic technique, fulfills such criteria and we have investigated the potential for the detection of the Cys282Tyr mutation. 100 subjects were genotyped using the heteroduplex approach. The results showed clear distinction between individuals who did not carry the mutation, individuals who were heterozygous for the mutation and homozygous individuals. Heteroduplex results obtained by both silver staining and capillary electrophoresis showed 100% concordance with those obtained by restriction digestion of PCR product.

1 The coumarin anticoagulant difenacoum was detected by high performance liquid chromatography (HPLC) with multi-wavelength UV detection in plasma from a 41 year old man who presented with a severe deficiency of vitamin K-dependent clotting factors of unknown aetiology. A longitudinal toxicological study of the consequent coagulopathy is described. 2 Plasma concentrations of difenacoum declined from 0.97 to 0.11 mgl-1 in 47 days with a terminal half life of 11.7 days. Rifampacin (300 mg bd) had no apparent effect on the terminal half life of the drug. Subsequently plasma concentrations of difenacoum and descarbox yprothrombin (DCP) unexpectedly increased. 3 Seven months after exposure clotting times were prolonged. The patient continued to have episodes of epistaxis, haematoma, purpurae and bruising and he required frequent treatment with Fresh Frozen Plasma in additional to oral phylloquinone (200 mg day-1). 4 Intermittent and unexpected increases in plasma concentrations of difenacoum and descarboxypro thrombin suggested that covert, repeated ingestion of the anticoagulant was the most likely cause of the poisoning. The measurement of low concentrations of plasma phylloquinone except following supervised ingestion ofthe vitamin indicated that as an outpatient, the subject was not compliant with treatment despite his protestations to the contrary. He continued to deny this even when confronted by laboratory findings and at no time did he ever admit to self-poisoning.

No abstract