Enrico Zammarchi

Biochemical evaluation of a patient with a familial form of leucine-sensitive hypoglycemia and concomitant hyperammonemia

A case of a child with recurrent episodes of severe hypoglycemia since the age of 6 months is reported. Biochemical evaluation extended to the first-degree relatives is consistent with a familial form of hypoglycemia due to a leucine-sensitive hyperinsulinism. In addition, this patient has a persistent elevation of serum ammonia levels of uncertain etiology that is more pronounced after meals. Urea cycle defects, organic acidurias, and beta-oxidation defects have been ruled out, as well as a possible excessive deamination of glucogenetic amino acids. This unexpected hyperammonemia, which was also detected in the mother, might be related to leucine hypersensitivity.

Genotype/phenotype correlation in glycogen storage disease type 1b: a multicentre study and review of the literature

We studied the genotype/phenotype correlation in a cohort of glycogen storage disease type (GSD) 1b patients. A total of 25 GSD1b patients, 13 females and 12 males, age range: 4.3–28.4 years, mean:14.6±6.8 years; median: 15 years, representing the entire case load of Italian GSD1b patients, were enrolled in the study. Molecular analysis of the glucose 6-phosphate translocase (G6PT1) gene was performed in all patients. We analysed the presence of a correlation among both the clinical features associated with GSD1b (neutropenia, frequency of admission to the hospital for severe infections) and the presence of systemic complications (liver adenomas, nephropathy, bone mineral density defect, polycystic ovaries, short stature, inflammatory bowel disease) and the mutations detected in each patient. Nine patients were homozygous or compound heterozygous for mutations causing stop codons. In particular, three patients were homozygous for the same mutation (400X); of these patients, one showed chronic neutropenia with severe and frequent infections and severe inflammatory bowel disease, another patient cyclic neutropenia associated with rare bacterial infections and mild bowel involvement and the last one normal neutrophil count. Two patients were homozygous for the mutation 128X; one of these patients did not show neutropenia, whereas the other one had severe neutropenia needing frequent hospital admission and was under granulocyte-colony stimulating factor treatment. In three patients no mutations were detected. Conclusion:no correlation was found between individual mutations and the presence of neutropenia, bacterial infections and systemic complications. These results suggest that different genes and proteins modulate neutrophil differentiation, maturation and apoptosis and thus the severity and frequency of infections. The absence of detectable mutations in three patients could suggest that a second protein plays a role in microsomal phosphate transport.

The inclusion of succinylacetone as marker for tyrosinemia type I in expanded newborn screening programs

In expanded newborn screening programs by liquid chromatography/tandem mass spectrometry false negatives for tyrosinemia type I are a significant problem. We describe a method for inclusion of succinylacetone in order to avoid false negatives. We studied spots from 13,000 neonates born in Tuscany (January-May 2007) and ten spots from six patients with tyrosinemia type I. The traditional screening method was modified by adding dioxooctanoid acid (or 13C2-succinylacetone) as an internal standard to the methanolic solution of deuterated acylcarnitines and amino acids. A hydrazine solution was added to the mixture. The times of extraction, butylation and drying were only slightly prolonged. Specific multiple reaction monitoring for derivatized and labelled succinylacetone and dioxooctanoic acid was carried out. The assays were linear up to 100 micromol/L for succinylacetone. Intra- and inter-day imprecision data were in the range of 1.34% to 7.09% and 3.50% to 4.49%. Limits of detection and of quantification were 0.2 micromol/L and 0.4 micromol/L, respectively. Recovery ranged from 97.02% to 100.29%. Succinylacetone levels in samples from unaffected neonates were very close to the detection limit. Of the 46 recalls, eight (17.4%) were for abnormal tyrosine levels and all these cases had succinylacetone levels within the normal range (<2.4 micromol/L). In ten spots from six affected patients succinylacetone values ranged from 3.3 to 35.0 micromol/L. Including succinylacetone in newborn screening programs for amino acids and acylcarnitines avoids false-negative results for tyrosinemia type I. Newborn screening laboratories should consider implementing these modifications.

Mother-to-infant transmission of hepatitis C virus.

Anti‐hepatitis C virus (HCV) antibodies and HCV‐RNA were measured in the sera of 22 anti‐HCV positive, HIV‐1 negative mothers and their infants. ELISA and RIBA II were used for anti‐HCV determination. HCV‐RNA was measured by a nested polymerase chain reaction. HCV‐RNA was found in 12 of 22 mothers. All 22 children were followed for 12 months. All were anti‐HCV positive by the fourth month; 18 became anti‐HCV negative between the 8th and 12th month. HCV‐RNA was detected in 5 of 22 infants in the fourth month. They remained HCV‐RNA positive. All children born to HCV‐RNA negative mothers were HCV‐RNA negative while 5 of 12 babies born to HCV‐RNA positive mothers were infected. All five infected babies were born to mothers infected through transfusions or drug use. ALT levels in mothers seemed to have no effect on mother‐to‐infant transmission. Hence evidence for perinatal transmission of HCV from HCV‐RNA positive mothers was demonstrated in the present study.

Structure and mutation analysis of the glycogen storage disease type 1b gene

Glycogen storage disease (GSD) 1b is the deficiency of endoplasmic reticulum glucose‐6‐phosphate (G6P) transport. We here report the structure of the gene encoding a protein likely to be responsible for G6P transport, and its mapping to human chromosome 11q23.3. The gene is composed of nine exons spanning a genomic region of approximately 4 kb. Primers based on the genomic sequence were used in single strand conformation polymorphism (SSCP) analysis and mutations were found in six out of seven GSD 1b patients analysed.

Hepatitis C virus antibodies in a long-term follow-up of beta-thalassaemic children with acute and chronic non-A non-B hepatitis

The presence of antibodies toward hepatitis C virus (HCV) was examined in 78 polytransfused betathalassaemic children. The anti-HCV status was correlated with acute and chronic non-A non-B (NANB) hepatitis that developed during a follow up of about 13 years. Anti-HCV was present in 83.3% of children with acute NANB hepatitis and in 82.9% of those with chronic NANB hepatitis. The percentage of chronic evolution was 56.7% for acute anti-HCV positive NANB hepatitis and 50.0% for anti-HCV negative NANB hepatitis. The long-term persistence of anti-HCV antibodies did not correlate with chronic evolution of liver infection in thalassaemic patients. Histological features of chronic hepatitis showed little or no difference between HCV associated or non-associated liver disease. The multifactorial liver injury in beta-thalassaemic children explains the high prevalence of cirrhosis (about 30%) observed in these patients with NANB hepatitis. On the other hand, independent of liver disease, some patients never seroconverted during the follow up in spite of the high number of transfusions suggesting the existence of “non-responders”.

Primary and Secondary Elastin-Binding Protein Defect Leads to Impaired Elastogenesis in Fibroblasts from GM1-Gangliosidosis Patients

G(M1)-gangliosidosis is a lysosomal storage disorder caused by acid beta-galactosidase deficiency. Aside from the lysosomal beta-galactosidase enzyme, the beta-galactosidase gene also encodes the elastin-binding protein (EBP), deficiency in which impairs elastogenesis. Using expression studies and Western blots of COS-1 cells, we identified and characterized four new and two known beta-galactosidase gene mutations detected in G(M1)-gangliosidosis patients with infantile, juvenile, or adult forms of disease. We then focused on impaired elastogenesis detected in fibroblasts from patients with infantile and juvenile disease. The juvenile patient showed connective-tissue abnormalities, unusual urinary keratan sulfate excretion, and an EBP reduction, despite mutations affecting only beta-galactosidase. Because galactosugar-bearing moieties may alter EBP function and impair elastogenesis, we assessed infantile and juvenile patients for the source of altered elastogenesis. We confirmed that the infantile patients impaired elastogenesis arose from a primary EBP defect, according to molecular analysis. We examined the juveniles fibroblasts by immunohistochemistry, addition of keratanase, soluble/insoluble elastin assay, and radiolabeling of tropoelastin. These experiments revealed that the juveniles impaired elastogenesis likely arose from secondary EBP deficiency caused by keratan sulfate accumulation. Thus, impaired elastogenesis in G(M1)-gangliosidosis can arise from primary or secondary EBP defects in fibroblasts from infantile and juvenile patients, respectively.

Gitelman Disease Associated with Growth Hormone Deficiency, Disturbances in Vasopressin Secretion and Empty Sella: A New Hereditary Renal Tubular-Pituitary Syndrome?

Gitelman disease was diagnosed in two unrelated children with hypokalemic metabolic alkalosis and growth failure (a boy and a girl aged 7 mo and 9.5 y, respectively, at clinical presentation) on the basis of mutations detected in the gene encoding the thiazide-sensitive NaCl cotransporter of the distal convoluted tubule. GH deficiency was demonstrated by specific diagnostic tests in both children. Hypertonic saline infusion tests showed a partial vasopressin deficiency in the girl and delayed secretion of this hormone in the boy. Magnetic resonance imaging revealed an empty sella in both cases. Up to now, hypomagnesemia and hypocalciuria have been considered obligatory criteria for the diagnosis of Gitelman disease; however, our two patients had hypomagnesia and hypocalciuria in less than half the determinations. GH replacement treatment was associated with a good clinical response in both children. It appears that these cases represent a new phenotype, not previously described in Gitelman disease, and that the entity may be considered a new complex hereditary renal tubular-pituitary syndrome.

The potential action of galactose as a "chemical chaperone": increase of beta galactosidase activity in fibroblasts from an adult GM1-gangliosidosis patient.

BACKGROUND The glycosphingolipid storage disorder GM1-gangliosidosis is a severe neurodegenerative condition for which no therapy is currently available. Protein misfolding in lysosomal defects may have the potential to be corrected by chemical chaperones: in vitro and clinical approaches are being investigated. AIMS We investigated the in vitro effect of galactose on some lysosomal hydrolases, and its in vitro efficacy as a chemical chaperone in GM1-gangliosidosis. METHODS Galactose was added to the culture medium of fibroblasts from patients, controls and transfected COS-1 cells. Enzyme assays of lysosomal hydrolases, beta galactosidase in particular, were performed. RESULTS Our data show that galactose alters selectively alpha and beta galactosidases. A significant increase (2,5 fold) in beta galactosidase activity occurred when galactose was added to the cultured fibroblasts of an adult patient. Chemical chaperone therapy requires the presence of residual enzyme activity. The adult patient here reported is heterozygous for the p.T329A mutation that showed no beta galactosidase activity, and for the p.R442Q mutation with residual enzyme activity. The p.R442Q mutation was therefore selected as a potential target for the galactose chaperone; after the addition of galactose, COS-1 cells transfected with this mutation showed an increase in beta galactosidase activity from 6.9% to 12% of control values. CONCLUSIONS These results suggest that galactose or its derivatives with potential chaperone properties could be used in the development of non-invasive therapies for GM1-gangliosidosis.

Severe prognosis in a large family with hypokalemic periodic paralysis.

Hypokalemic periodic paralysis (HypoPP) is a channel disorder caused primarily by mutations in the human skeletal muscle α1 subunit (CACNA1S) of the dihydropyridine‐sensitive calcium channel. Molecular, clinical, and biochemical studies were aimed at establishing genotype/phenotype correlations in a large Italian family affected by a severe form of HypoPP. Whereas patients with HypoPP usually show a normal life span, in this family three male patients died young, one of them from anesthetic complications resembling malignant hyperthermia. Our patients carried the c1583G>A genetic lesion (R528H), which has been associated with a mild phenotype and with incomplete penetrance in women. Surprisingly, the R528H amino acid substitution in the family presented here correlated with an unfavorable prognosis in both male and female patients. We conclude that genetic characterization is an important requirement to alert physicians about the management of similar patients, especially when anesthesia is considered. Muscle Nerve 27: 165–169, 2003