Novel Mutation in GALT Gene in Galactosemia Patient with Group B Streptococcus Meningitis and Acute Liver Failure.

Classic galactosemia is an autosomal recessive disorder caused by the deficiency of the enzyme galactose-1-phosphate uridyltransferase (GALT) involved in galactose metabolism. Bacterial infections are a known cause of early morbidity and mortality in children with classic galactosemia. The most common agent is Escherichia coli, but in rare situations, other bacteria are incriminated. We report a case of a three-week-old female patient with galactosemia, who presented with Group B Streptococcus (GBS) meningitis/sepsis. She received treatment with antibiotics, supportive therapy, and erythrocyte transfusion, but after a short period of improvement, she presented acute liver failure with suspicion of an inborn error of metabolism. Rapid nuclear magnetic resonance (NMR) spectroscopy from urine showed highly elevated values of galactose and galactitol. Under intensive treatment for acute liver failure and with a lactose-free diet, her clinical features and laboratory parameters improved considerably. Genetic testing confirmed compound heterozygous status for GALT mutations: c.563 A>G [p.Q188R] and c. 910 C>T, the last mutation being a novel mutation in GALT gene. In countries without an extensive newborn screening program, a high index of suspicion is necessary for early diagnosis and treatment of galactosemia.

Assessment of lactase activity in humans by measurement of galactitol and galactonate in serum and urine after milk intake.

Background: Lactase is an enzyme that hydrolyzes lactose into glucose and galactose in the small intestine, where they are absorbed. Hypolactasia is a common condition, primarily caused by genetic programming, that leads to lactose maldigestion and, in certain cases, lactose intolerance. Galactitol and galactonate are 2 products of hepatic galactose metabolism that are candidate markers for the intake of lactose-containing foods. Objectives: The primary objective of the study was to explore the changes in serum and urine metabolomes during postprandial dairy product tests through the association between lactase persistence genotype and the postprandial dynamics of lactose-derived metabolites. Methods: We characterized the 6-h postprandial serum kinetics and urinary excretion of lactose, galactose, galactitol, and galactonate in 14 healthy men who had consumed a single dose of acidified milk (800 g) which contained 38.8 g lactose. Genotyping of LCT-13910 C/T (rs4988235) was performed to assess primary lactase persistence. Results: There were 2 distinct postprandial responses, classified as high and low metabolite responses, observed for galactose, and its metabolites galactitol and galactonate, in serum and urine. In all but 1 subject, there was a concordance between the high metabolite responses and genetic lactase persistence and between the low metabolite responses and genetic lactase nonpersistence (accuracy 0.92), galactitol and galactonate being more discriminative than galactose. Conclusions: Postprandial galactitol and galactonate after lactose overload appear to be good proxies for genetically determined lactase activity. The development of a noninvasive lactose digestion test based on the measurement of these metabolites in urine could be clinically useful. This trial was registered at clinicaltrials.gov as NCT02230345.

Early diet impacts infant rhesus gut microbiome, immunity, and metabolism.

Epidemiological research has indicated a relationship between infant formula feeding and increased risk of chronic diseases later in life including obesity, type-2 diabetes, and cardiovascular disease. The present study used an infant rhesus monkey model to compare the comprehensive metabolic implications of formula- and breast-feeding practices using NMR spectroscopy to characterize metabolite fingerprints from urine and serum, in combination with anthropometric measurements, fecal microbial profiling, and cytokine measurements. Here we show that formula-fed infants are larger than their breast-fed counterparts and have a different gut microbiome that includes higher levels of bacteria from the Ruminococcus genus and lower levels of bacteria from the Lactobacillus genus. In addition, formula-fed infants have higher serum insulin coupled with higher amino acid levels, while amino acid degradation products were higher in breast-fed infants. Increases in serum and urine galactose and urine galactitol were observed in the second month of life in formula-fed infants, along with higher levels of TNFα, IFN-γ, IL-1ß, IL-4, and other cytokines and growth factors at week 4. These results demonstrate that metabolic and gut microbiome development of formula-fed infants is different from breast-fed infants and that the choice of infant feeding may hold future health consequences.

Long-term complications in Estonian galactosemia patients with a less strict lactose-free diet and metabolic control.

The main aim of our study was to retrospectively evaluate long-term complications and measure urinary galactose and galactitol excretion in classical galactosemia patients in Estonia who have been treated with a less restricted lactose-free diet and metabolic control. Our study group consisted of five classical galactosemia patients aged 7-14 years and diagnosed since 1996 in Estonia. Their diet eliminates lactose present in dairy foods, but we did not restrict the consumption of mature cheeses, fruits and vegetables. All patients had normal growth, except for one patient who was overweight at the last evaluation. In three patients mental and speech development was normal. One patient, number 1, who was diagnosed latest (at 6 weeks of age), had moderate mental retardation, verbal dyspraxia, extrapyramidal signs and bilateral cataracts. In both patients with developmental problems, a brain MRI showed bilateral subcortical changes in the cerebral white matter. Of four females, only patient 4 (p.Q188R homozygote) has premature ovarian insufficiency. Urinary galactose and galactitol content were retrospectively measured using high-performance liquid chromatography and refractive-index detection from urinary samples that were preserved during the years 1996-2009. Galactose ranged from 60 to 600 mmol/mol creatinine (normal=4-6), and galactitol ranged from 70 to 1200 mmol/mol creatinine (normal=2-4), which was 10-100 and 17-300 times higher than the respective reference ranges for galactose and galactitol. We conclude that a less strict lactose-free diet and metabolic control performed in Estonian classical galactosemia patients does not change long-term outcome compared to previously published studies.

Monitoring of biochemical status in children with Duarte galactosemia: utility of galactose, galactitol, galactonate, and galactose 1-phosphate.

BACKGROUND: Duarte galactosemia (DG) is frequently detected in newborn-screening programs. DG patients do not manifest the symptoms of classic galactosemia, but whether they require dietary galactose restriction is controversial. We sought to assess the relationships of selected galactose metabolites (plasma galactose, plasma galactitol, erythrocyte (RBC) galactitol, RBC galactonate, and urine galactitol and galactonate) to RBC galactose 1-phosphate (Gal-1-P), dietary galactose intake, and neurodevelopmental/clinical outcomes in DG children. METHODS: We studied 30 children 1-6 years of age who had DG galactosemia and were on a regular diet. All participants underwent a physical and ophthalmologic examination and a neurodevelopmental assessment. RBC galactitol, RBC galactonate, RBC Gal-1-P, plasma galactose, plasma galactonate, and urine galactitol and galactonate concentrations were measured. RESULTS: RBC galactitol and galactonate concentrations were about 2 and 6 times higher, respectively, than control values. Plasma galactose and galactitol concentrations were also about twice the control values. The mean values for RBC Gal-1-P and urine galactitol were within the reference interval. We found a relationship between plasma and urine galactitol concentrations but no relationship between RBC galactose metabolites and urine galactitol. There was a significant relationship between galactose intake and RBC galactose metabolites, especially RBC galactitol (P < 0.0005) and RBC galactonate (P < 0.0005). Galactose intake was not related to the urine galactitol, plasma galactose, or plasma galactitol concentration. RBC galactitol, RBC galactonate, plasma galactose, plasma galactitol, and urine galactonate concentrations showed no relationship with clinical or developmental outcomes. CONCLUSIONS: DG children on a regular diet have RBC Gal-1-P concentrations within the reference interval but increased concentrations of other galactose metabolites, including RBC galactitol and RBC galactonate. These increased concentrations correlate with galactose intake and neither cause any developmental or clinical pathology during early childhood nor oblige a lactose-restricted diet.

Outcomes of siblings with classical galactosemia.

OBJECTIVES: To determine the long-term outcome of dietary intervention in siblings from 14 Irish families with classical galactosemia (McKusick 230400), an autosomal recessive disorder of carbohydrate metabolism and galactose-1-phosphate uridyltransferase (GALT) deficiency. STUDY DESIGN: Outcomes in siblings on dietary galactose restriction were studied to evaluate whether birth order (ie, time of commencement of diet) and compliance with lactose-restricted diet (galactose intake > or < 20 mg /day), assessed by dietary recall and biochemical monitoring of galactose-1-phosphate [Gal-1-P] and galactitol values, affected outcomes. The outcome variables assessed were IQ, speech, and language assessment scores, neurologic examination results, and magnetic resonance imaging (MRI) of the brain. RESULTS: There was a high incidence of complications in the overall group, particularly speech and language delay (77%) and low IQ (71%). There was no significant difference in outcome between earlier-treated and later-treated siblings or any correlation with mean Gal-1-P or galactitol values. In most cases, cerebral white matter disease was evident on MRI scanning, with evidence of progressive cerebellar degeneration seen in 2 highly compliant families. CONCLUSION: The subjects with a higher galactose intake did not exhibit an increased incidence of complications; conversely, those who were very compliant with dietary restrictions did not have more favorable outcomes.

Duarte (DG) galactosemia: a pilot study of biochemical and neurodevelopmental assessment in children detected by newborn screening.

UNLABELLED: Newborn screening for galactosemia has shown a high prevalence of partial galactose uridyl transferase deficiencies such as Duarte (DG) galactosemia. STUDY OBJECTIVE: To determine whether (a) there is any clinical impact of DG galactosemia on development (b) there is a relationship between outcome and biochemical parameters in patients who receive no treatment. STUDY POPULATION: Twenty-eight children with DG galactosemia. Group-I-17 children had a lactose restricted diet in the first year of life. Group-II-11 children had a regular diet since birth. METHODS: Developmental, physical, and ophthalmologic assessments were completed on both DG groups. RBC gal-1-p and urine galactitol were monitored during the follow-up visits in every child with DG galactosemia. Gal-1-p, urine galactitol, liver function tests, and FSH were tested at the time of study visit. RESULTS: The groups had statistically significant differences on RBC gal-1-p and urine galactitol at the 2 week, 1 month, 6 month, and 1 year time points. There was no statistical difference of gal-1-p or urine galactitol in group-I and -II at the time of study. The groups had statistically significant differences on adaptive scores, but not on language or IQ. None of the DG subjects had abnormal liver function at the time of diagnosis or the study visit. The FSH levels were normal. There were no statistically significant relationships between the first year metabolic values and developmental outcomes. CONCLUSIONS: The data presented here indicate that clinical and developmental outcomes in DG galactosemics are good regardless of any diet changes.

Pregnancy and lactation in a woman with classical galactosaemia heterozygous for p.Q188R and p.R333W.

A 31-year old patient who is compound heterozygous for the two galactose-1-phosphate uridyltransferase mutations p.Q188R and p.R333W delivered two healthy boys after uneventful spontaneous pregnancies. The patient chose to breast-feed her first baby and her galactose metabolites in blood and urine were monitored closely. A temporary increase in her galactose-1-phosphate (gal-1-P) levels with a maximum of 0.30 mmol/L on day 2 after delivery was observed. Galactose-1-phosphate was normalized 10 days after delivery. At the time of weaning, 8 months after delivery, her menses returned and she had normal sex steroid levels. She became pregnant again 2 months later. The second baby was also breast-fed. This time an increase in her gal-1-P values could be seen for 3 weeks with a maximum gal-1-P level of of 0.25 mmol/L at day 7. Only minor changes in her urine galactitol values were noted during the study period but the values stayed in the range of treated galactosaemia patients. We thus report that breast-feeding has been possible with only small adverse effects on the levels of galactose metabolites in a patient with classical galactosaemia.

Two familial cases of high blood galactose of unknown aetiology.

We report two male siblings presenting as newborns with increased blood galactose, urinary excretion of galactitol, and normal galactose 1-phosphate on a breast milk diet. A lactose-free diet led to normalization of all metabolites, while reintroduction of galactose in the diet resulted in an accumulation of metabolites. Potential causes of galactosaemia include: (1) activities of three enzymes of galactose metabolism: galactokinase (GALK), galactose-1-phosphate uridyltransferase (GALT), and uridine diphosphate galactose 4'-epimerase (GALE), (2) portosystemic shunting, (3) Fanconi-Bickel syndrome, (4) tyrosinaemia. Each was excluded with appropriate tests. These two familial cases may represent a novel autosomal or X-linked recessive disorder of galactose metabolism, possibly due to a novel defect in the transport of galactose across the plasma membrane.

Proton MR spectroscopy and imaging of a galactosemic patient before and after dietary treatment.

We describe how proton MR spectroscopy ((1)H-MR spectroscopy) was useful in elucidating the diagnosis of galactosemia in an undiagnosed 6-month-old infant. In vivo (1)H-MR spectroscopy of the brain showed a doublet at 3.7 parts per million, which was identified as galactitol (Gal-ol) by in vitro (1)H-MR spectroscopy of the urine. Galactosemia was subsequently confirmed by laboratory tests and treatment was initiated. A follow-up brain MR imaging and (1)H-MR spectroscopy study revealed resolution of white matter lesions and disappearance of Gal-ol peaks.

Urinary galactitol and galactonate quantified by isotope-dilution gas chromatography-mass spectrometry.

BACKGROUND: Measurements of urine galactitol have been used to monitor the adequacy of diet therapy in the treatment of galactosemia. We have devised a gas chromatographic mass spectrometry (GC/MS) isotope-dilution method for the simultaneous quantification of urine galactitol and another alternate pathway product, galactonate. METHODS: We prepared trimethylsilyl (TMS) derivatives and used D-[UL-13C]galactitol and D-[UL-13C]galactonate as the internal standard for GC/MS. Results obtained with this method were compared with those determined by the established GC method for galactitol and the NMR method for galactonate. Thirty-three normal urine specimens were analyzed by the isotope dilution technique for galactitol and galactonate. Results of galactitol in 6 of these urine specimens along with 18 from classic galactosemics and 19 variant galactosemics were compared with the established GC method. Results for galactonate in 15 urine specimens from galactosemics were compared to the established NMR technique. RESULTS: The method was linear up to 200 nmol with lower limits of detection of 1.1 nmol (1.75 mmol/mol creatinine) (Cr) and 0.8 nmol (1.28 mmol/mol Cr) for galactitol and galactonate, respectively. Intra- and Interassay imprecision ranged from 2.1-6.7% for galactitol and 3.5-8.0% for galactonate. The excretion of both metabolites was age dependent in both normal and galactosemics. In 12 normal urines from subjects under 1 year, values for galactitol ranged from 8-107 mmol/mol Cr, and in 7 over age 6, ranged from 2-5 mmol/mol Cr. Under 1 year, the range for galactonate was non-detectable to 231 and in the over 6 years group non-detectable to 25 mmol/mol Cr. In galactosemics under 1 year, the value for galactitol ranged from 397-743 and for galactonate 92-132 mmol/mol Cr while in nine patients over age 6 the range was 125-274 mmol/mol Cr for galactitol and 17-46 mmol/mol Cr for galactonate. CONCLUSIONS: The GC/MS method enables the simultaneous determination of urine galactitol and galactonate and is precise and useful over the wide range of concentrations needed to assess the galactose burden in patients with galactosemia.

Analysis of polyols in urine by liquid chromatography-tandem mass spectrometry: a useful tool for recognition of inborn errors affecting polyol metabolism.

Several inborn errors of metabolism with abnormal polyol concentrations in body fluids are known to date. Most of these defects can be diagnosed by the assessment of urinary concentrations of polyols. We present two methods using tandem mass spectrometry for screening for inborn errors affecting polyol metabolism. Urine samples supplemented with internal standards ([13C4]erythritol, [13C2]arabitol and [2H3]sorbitol) were desalted by a mixed-bed ion-exchange resin. Separation was achieved by two different columns. Sugar isomers could not be separated using a Prevail Carbohydrate ES 54 column (method 1), whereas with the other column (Aminex HPX-87C) separation of the isomers was achieved (method 2). Multiple reaction monitoring polyol detection was achieved by tandem mass spectrometry with an electron ion-spray source operating in the negative mode. Age-related reference ranges of polyols (erythritol, treitol, arabitol, ribitol, xylitol, galactitol, mannitol, sorbitol, sedoheptitol and perseitol) in urine were established. The applicability of the method was demonstrated by the abnormal polyol concentrations observed in patients with transaldolase deficiency, ribose-5-phosphate isomerase deficiency and classical galactosaemia. This paper describes two methods for the analysis of urinary polyols by liquid chromatography-tandem mass spectrometry. Method 1 is a fast screening method with the quantification of total isomers and method 2 is a more selective method with the separate quantification of the polyols. Both methods can be used for diagnosing inborn errors of metabolism affecting polyol metabolism.

High tolerance for oral galactose in classical galactosaemia: dietary implications.

AIM: To study the relevance of restricting the exogenous intake of small amounts of galactose, such as from fruit and vegetables, in patients with classical galactosaemia. METHODS: For a period of six weeks, increasing doses of oral galactose to a maximum of 600 mg per day, were added to a very strict galactose restricted diet in three adolescent patients homozygous for the Q188R mutation. During the study, physical examination, including an extended ophthalmic examination, and laboratory studies were performed on a weekly basis. RESULTS: No significant change in any of the studied clinical or biochemical parameters was observed. CONCLUSIONS: These findings provide further evidence that attempts to exclude trace amounts of galactose from the diet are not justified. Once the diet is made more liberal, a long term follow up study will be necessary.

Age dependence of endogenous galactose formation in Q188R homozygous galactosemic patients.

The age dependence of endogenous galactose formation was investigated in Q188R homozygous galactosemic patients (n=18; 4-38 years) using the primed continuous infusion approach with D-[1-13C]galactose as a substrate. Studies were conducted under postabsorptive conditions (fasting >10h) and good metabolic control. In the patients, the release of galactose from endogenous sources into plasma (R(a)) decreased with age and ranged from 4.6 to 2.0 micromol/kg body weight per h. Galactitol and galactonate release rates paralleled the galactose R(a) but at a lower level. The mean relation of galactose, galactitol, and galactonate release was 10:5:1. Statistically, there was a highly significant (p<0.0001) inverse correlation between total galactose release (i.e., sum of R(a) plus galactitol and galactonate release) and age. The data (total galactose=y, age=t) were best fitted to the simple exponential model y=y(0)+axexp(-bt) by non-linear regression analysis. The parameter estimates were y(0)=3.0+/-0.2, a=6.5+/-0.4, and b=0.11+/-0.02. The value of y(0) provides an estimate of total galactose release in adult patients (i.e., approximately 13 mg/kg body weight per day), summation operator (y(0)+a) provides an estimate for galactosemic newborns (i.e., approximately 41 mg/kg body weight per day). The data show that significant amounts of endogenous galactose are formed in galactosemic patients with release rates being several fold higher in infants than in adults. The present findings can explain the persistently elevated galactose-1-phosphate levels in erythrocytes-and its age dependence-in galactosemic patients even when under strict dietary treatment.

Galactonate determination in urine by stable isotope dilution gas chromatography-mass spectrometry.

A stable isotope dilution assay was developed for the sensitive determination of D-galactonic acid. D-[U-13C(6)]galactono-1,4-lactone was prepared as internal standard. Unlabelled and U-13C-labelled D-galactonic acid species were converted to the N-(1-butyl)galactonamide pentaacetate derivatives and assessed by gas chromatography-mass spectrometry (GC-MS). Positive chemical ionisation and monitoring of the [MH-60](+)-ions in the galactonate chromatographic peak at m/z 402 and m/z 408 were used for quantification. The procedure was applied to study the variability of D-galactonate excretion in healthy subjects and galactosemic patients and to monitor the D-galactonate-D-galactitol ratio in human urine.

Renal excretion of galactose and galactitol in patients with classical galactosaemia, obligate heterozygous parents and healthy subjects.

The age dependence of galactose and galactitol excretion was assessed in overnight-fasted galactose-1-phosphate uridyltransferase-deficient patients under dietary treatment (ages 4-34 years; n = 51), obligate heterozygous parents (ages 25-71 years; n = 49) and healthy subjects (ages 3-58 years; n = 215). Urine concentrations were analysed by stable-isotope dilution gas chromatography mass spectrometry. There was considerable interindividual variability. The intraindividual variation, however, was not age-dependent and was rather low. Excretion estimates were calculated from the creatinine-related concentrations using weight-, age- and sex-related creatinine excretion rates. Experimental evidence is presented underscoring the problems inherent in random sampling and substantiating the primary endogenous origin of galactose and galactitol in postabsorptive urine samples. Age-dependent excretion estimates were best fitted to a simple growth-related model assuming an exponential decrease with age until adulthood. According to the model, mean postabsorptive galactose and galactitol excretion in healthy subjects was similar and decreased exponentially from about 1.2 micromol/kg body weight per day in infants to about 0.2 micromol/kg body weight per day in adults. Excretion in heterozygotes was normal. In galactosaemic patients, galactose excretion was in the normal range. Galactitol excretion, however, was enhanced over 50-fold and decreased from a mean estimate of about 64 micromol/kg body weight per day in infants to about 23 micromol/kg body weight per day in adults. The results are discussed with respect to the significance of galactose and galactitol excretion for whole-body galactose removal and with respect to the applicability of urinary galactitol analysis for metabolic monitoring in galactosaemia.

Verbal dyspraxia and galactosemia.

Classical galactosemia is an autosomal recessive disorder resulting from deficient galactose-1-phosphateuridyl transferase (GALT) activity. Verbal dyspraxia is an unusual outcome in galactosemia. Here we validated a simplified breath test of total body galactose oxidation against genotype and evaluated five potential biochemical risk indicators for verbal dyspraxia in galactosemia: cumulative percentage dose (CUMPCD) of (13)CO(2) in breath, mean erythrocyte galactose-1-phosphate, highest erythrocyte galactose-1-phosphate, mean urinary galactitol, and erythrocyte GALT activity. Thirteen controls and 42 patients with galactosemia took a (13)C-galactose bolus, and the (CUMPCD) of (13)CO(2) in expired air was determined. Patients with <5% CUMPCD had mutant alleles that severely impaired human GALT enzyme catalysis. Patients with > or =5% CUMPCD had milder mutant human GALT alleles. Twenty-four patients consented to formal speech evaluation; 15 (63%) had verbal dyspraxia. Dyspraxic patients had significantly lower CUMPCD values (2.84 +/- 5.76% versus 11.51 +/- 7.67%; p < 0.008) and significantly higher mean erythrocyte galactose-1-phosphate (3.38 +/- 0.922 mg/dL versus 1.92 +/- 1.28 mg/dL; p = 0.019) and mean urinary galactitol concentrations (192.4 +/- 75.8 mmol/mol creatinine versus 122.0 +/- 56.4; p = 0.048) than patients with normal speech. CUMPCD values <5%, mean erythrocyte galactose-1-phosphate levels >2.7 mg/dL, and mean urinary galactitol levels >135 mmol/mol creatinine were associated with dyspraxic outcome with odds ratios of 21, 13, and 5, respectively. We conclude that total body oxidation of galactose to CO(2) in expired air reflects genotype and that this breath test is a sensitive predictor of verbal dyspraxia in patients with galactosemia.

Urine and plasma galactitol in patients with galactose-1-phosphate uridyltransferase deficiency galactosemia.

Urinary excretion of galactitol was determined in 95 normals (N/N), 67 galactosemic (G/G), and 39 compound heterozygotes for the Duarte and galactosemia genotype (D/G). Galactitol excretion is age-dependent in both normal individuals and patients with classic galactosemia on lactose-restricted diets. In galactosemic patients who are homozygous for the Q188R mutation, urinary galactitol levels were fivefold to 10-fold higher than those of normal subjects of comparable age. All but a few patients with classic galactosemia with the Q188R mutation and another mutant G allele had urinary excretion comparable to the Q188R homozygous patients. African-American galactosemic patients with the S135L mutation of the galactose-1-phosphate uridyltransferase (GALT) gene also excreted abnormal quantities of galactitol. Most subjects with a Duarte allele and a G allele excrete normal amounts of the sugar alcohol. There is a correlation between galactitol excretion and red blood cell (RBC) galactose-1-phosphate (gal-1-P). Plasma galactitol was also elevated in galactosemic patients (3.4 to 23.2 micromol/L; undetectable in normal individuals). In contrast to the decrease in urinary galactitol with age, plasma levels remain in a narrow concentration range with no significant difference with age. Urine and plasma galactitol distinguish galactosemic patients from normals. In addition, urinary galactitol excretion may be an important parameter for the assessment of steady-state galactose metabolism in galactosemia.

Biochemical monitoring of treatment for galactosaemia: biological variability in metabolite concentrations.

Red cell galactose 1-phosphate (Gal-1-P) concentrations and urinary galactitol excretion have been suggested as biochemical indices of dietary compliance in classical transferase-deficient galactosaemia. We report our experience of measuring both in 32 patients over 0-10.9 years (median 3.45). A total of 438 blood specimens for Gal-1-P and 383 urine specimens for galacitol assay were received; 317 pairs of specimens were collected at the same time. Concentrations of both analytes fell rapidly over the first 2-3 months following dietary intervention, to mean (geometric SD) levels of 225 (1.60) mumol/L red cells for Gal-1-P and 388 (1.19) mumol/mmol creatinine for galactitol. Concentrations then fell exponentially over the next 7-8 years, with times to half-disappearance of 6.3 years for Gal-1-P and 6.4 years for galactitol, to levels of 104 (1.58) and 193 (1.36) respectively in patients aged over 10 years. Concentrations of both analytes were independent of the presence of the common Q188R mutation. Mean intra- and inter-individual coefficients of variation (CV) across the range of values studied were 36% and 61% for Gal-1-P, and 37% and 42% for galactitol. Analytical CVs were 3.6% for Gal-1-P and 5.5% for galactitol, indicating that the major source of variability is biological. The correlation coefficient between Gal-1-P and galactitol in paired samples overall was 0.33; the regression equation being [Galactitol] = 0.84[Gal-1-P] + 176. Serial measurements of both Gal-1-P and galactitol may be valuable in monitoring galactosaemia, but high intra-individual biological variability limits their usefulness. Standardization of sample collection times may improve this. Further work is needed to assess the predictive values of both analytes for long-term outcome.