Mutations in the aldolase B gene (ALDOB) impairing enzyme activity toward fructose-1-phosphate cleavage cause hereditary fructose intolerance (HFI). Diagnosis of the disease is possible by identifying known mutant ALDOB alleles in suspected patients; however, the frequencies of mutant alleles can differ by population. Here, 153 American HFI patients with 268 independent alleles were analyzed to identify the prevalence of seven known HFI-causing alleles (A149P, A174D, N334K, Δ4E4, R59Op, A337V, and L256P) in this population. Allele-specific oligonucleotide hybridization analysis was performed on polymerase chain reaction (PCR)-amplified genomic DNA from these patients. In the American population, the missense mutations A149P and A174D are the two most common alleles, with frequencies of 44% and 9%, respectively. In addition, the nonsense mutations Δ4E4 and R59Op are the next most common alleles, with each having a frequency of 4%. Together, the frequencies of all seven alleles make up 65% of HFI-causing alleles in this population. Worldwide, these same alleles make up 82% of HFI-causing mutations. This difference indicates that screening for common HFI alleles is more difficult in the American population. Nevertheless, a genetic screen for diagnosing HFI in America can be improved by including all seven alleles studied here. Lastly, identification of HFI patients presenting with classic symptoms and who have homozygous null genotypes indicates that aldolase B is not required for proper development or metabolic maintenance.

A6-month-old male infant was sent to a quaternary referral hospital from a tertiary referral hospital with a possible diagnosis of a fatty acid oxidation disorder. HISTORY OF PRESENTING ILLNESSThe infant was well until 4 weeks before admission at the quaternary referral hospital. He, along with the rest of his family, experienced an acute gastroenteritic illness with vomiting and watery diarrhea. Although his siblings and parents recovered, he did not, and because of concerns of a presumed secondary lactose intolerance he was changed from his usual Similac (Ross Products, Abbott Laboratories, Columbus, Oh) formula to a soy-based formula (Alsoy, Nestle Inc, Eau Claire, Wisc) about one week into his illness. He became more lethargic and hypotonic with persisting vomiting and diarrhea, and was admitted to a tertiary referral hospital. PAST HISTORYHe was born to nonconsanguineous parents of Italian (father) and Hungarian-French (mother) descent. He had two female siblings both of whom had been well in the past, and there was no family history of notable diseases. During pregnancy his mother had a laparoscopic cholecystectomy at 20 weeks' gestation, and he was born by Cesarean delivery at term because of fetal bradycardia. There were no other problems in the perinatal period. He had been well before this current illness, with appropriate growth parameters and development. He was fed a combination of breast milk and formula (Similac, Ross Pharmaceuticals). Cereals were introduced at 5 months along with other age-appropriate foods such as bananas and some vegetables. TERTIARY REFERRAL HOSPITALSymptoms of diarrhea and poor feeding had persisted for approximately two weeks before admission to the tertiary referral hospital, where he was found to be weak, floppy, and lethargic but easily rousable. He had massive hepatomegaly, with the liver edge palpable in the right iliac fossa, which had not been previously noted on several abdominal examinations. There was no splenomegaly, ascites, or signs of chronic liver disease. He was not clinically jaundiced despite elevated conjugated bilirubin. An Escherichia coli urinary tract infection (UTI) was Initial hematology and biochemical results are shown in Tables I and II. Of note is the presence of hypoglycemia, hypokalemia, hypophosphatemia, low plasma carnitine levels, hepatic dysfunction and coagulopathy. Other investigations that were normal included venous blood gas, plasma lactate, amino acids, creatine kinase, galactosemia screen, and routine urinalysis (ketones negative). Gas chromatography mass spectroscopy analysis of urinary organic acids showed elevated dicarboxylic acids with hypoketosis at the time of hypoglycemia. Urinary succinylacetone was negative. Serology for hepatitis viruses A, B, and C was negative. An echocardiogram demonstrated thickening of the interventricular septum, suggestive of a possible cardiomyopathy. An abdominal ultrasonogram showed an enlarged, heterogeneous liver with increased echogenicity and normal portal flow. A liver biopsy was performed ...

An accumulation of expressed sequence tag (EST) data in the public domain and the availability of bioinformatic programs have made EST gene expression profiling a common practice. However, the utility and validity of using EST databases (e.g., dbEST) has been criticized, particularly for quantitative assessment of gene expression. Problems with EST sequencing errors, library construction, EST annotation, and multiple paralogs make generation of specific and sensitive qualitative and quantitative expression profiles a concern. In addition, most EST-derived expression data exists in previously assembled databases. The Virtual Northern Blot (VNB) (http://tlab.bu.edu/vnb.html) allows generation, evaluation, and optimization of expression profiles in real time, which is especially important for alternatively spliced, novel, or poorly characterized genes. Representative gene families with variable nucleotide sequence identity, tissue specificity, and levels of expression (bcl-xl, aldoA, and cyp2d9) are used to assess the quality of VNB’s output. The profiles generated by VNB are more sensitive and specific than those constructed with ESTs listed in preindexed databases at UCSI and NCBI. Moreover, quantitative expression profiles produced by VNB are comparable to quantization obtained from Northern blots and qPCR. The VNB pipeline generates real-time gene expression profiles for single-gene queries that are both qualitatively and quantitatively reliable.