Budd-Chiari syndrome associated with coagulation abnormalities in a child with carbohydrate deficient glycoprotein syndrome type Ix

Defining the phenotype in congenital disorder of glycosylation due to ALG1 mutations

Deficiency of β-1,4 mannosyltransferase (MT-1) congenital disorder of glycosylation (CDG), due to ALG1 gene mutations. Features in 9 patients reported previously consisted of prenatal growth retardation, pregnancy-induced maternal hypertension and fetal hydrops. Four patients died before 5 years of age, and survivors showed a severe psychomotor retardation. We report on 7 patients with psychomotor delay, microcephaly, strabismus and coagulation abnormalities, seizures and abnormal fat distribution. Four children had a stable clinical course, two had visual impairment, and 1 had hearing loss. Thrombotic and vascular events led to deterioration of the clinical outcome in 2 patients. Four novel ALG1 mutations were identified. Pathogenicity was determined in alg1 yeast mutants transformed with hALG1. Functional analyses showed all novel mutations representing hypomorphs associated with residual enzyme activity. We extend the phenotypic spectrum including the first description of deafness in MT1 deficiency, and report on mildly affected patients, surviving to adulthood. The dysmorphic features, including abnormal fat distribution and strabismus highly resemble CDG due to phosphomannomutase-2 deficiency (PMM2-CDG), the most common type of CDG. We suggest testing for ALG1 mutations in unsolved CDG patients with a type 1 transferrin isoelectric focusing pattern, especially with epilepsy, severe visual loss and hemorrhagic/thrombotic events.

Radiologic and neurophysiologic aspects of stroke-like episodes in children with congenital disorder of glycosylation type Ia

In an effort to shed light on the mechanism of hemiparetic stroke-like events experienced by patients with congenital disorder of glycosylation type Ia, we evaluated 3 children with this disorder by brain imaging studies and continuous electroencephalogram monitoring during such events. No evidence of ischemia or infarction was revealed on imaging studies and electrographic seizures or intermittent epileptiform activity was demonstrated on electrographic recordings. All 3 patients showed clinical and electrographic improvement after administration of antiepileptic medication. Epileptic phenomena can complicate the stroke-like events of patients with congenital disorder of glycosylation type Ia, and the cause of the hemiparesis may indeed be an active epileptic inhibitory process. As such, electroencephalogram monitoring is warranted, and treatment with anticonvulsant agents is indicated.

Komrower Lecture. Congenital disorders of glycosylation (CDG): it's all in it!

Congenital disorders of glycosylation (CDGs) are due to defects in the synthesis of the glycan moiety of glycoproteins or other glycoconjugates. This review is devoted mainly to the clinical aspects of protein glycosylation defects. There are two main types of protein glycosylation: N-glycosylation and O-glycosylation. N-glycosylation generally consists of an assembly pathway (in cytosol and endoplasmic reticulum) and a processing pathway (in endoplasmic reticulum and Golgi). O-glycosylation lacks a processing pathway but is otherwise more complex. Sixteen disease-causing defects are known in protein glycosylation: 12 in N-glycosylation and four in O-glycosylation. The N-glycosylation defects comprise eight assembly defects (CDG-I) designated CDG-Ia to CDG-Ih, and four processing defects (CDG-II) designated CDG-IIa to CDG-IId. By far the most frequent is CDG-Ia (phosphomannomutase-2 deficiency). It affects the nervous system and many other organs. Its clinical expression varies from extremely severe to very mild (and thus probably underdiagnosed). The most interesting disease in this group is CDG-Ib (phosphomannose isomerase deficiency) because it is so far the only efficiently treatable CDG (mannose treatment). It has a hepatic-intestinal presentation. The O-glycosylation defects comprise two O-xylosylglycan defects (a progeroid variant of Ehlers-Danlos syndrome and the multiple exostoses syndrome) and two O-mannosylglycan defects (Walker-Warburg syndrome and muscle-eye-brain disease). All known CDGs have a recessive inheritance except for multiple exostoses syndrome, which is dominantly inherited. There is a rapidly growing group of putative CDGs with a large spectrum of clinical presentations (CDG-x). Serum transferrin iso-electrofocusing remains the cornerstone of the screening for N-glycosylation defects associated with sialic acid deficiency. Abnormal patterns can be grouped in to type 1 and type 2. However, a normal pattern does not exclude these defects. Screening for the other CDGs is much more difficult, particularly when the defect is organ- or system-restricted. The latter group promises to become an important new chapter in CDG. It is concluded that CDGs will eventually cover the whole clinical spectrum of paediatric and adult disease manifestations.

Repeat interventions for maintenance of transjugular intrahepatic portosystemic shunt function in patients with Budd-Chiari syndrome

The authors report the role of transjugular intrahepatic portosystemic shunts (TIPS) and consecutive interventions, including brachytherapy (n = 2) and stent-graft placement (n = 3), to increase secondary patency and consequently postpone orthotopic liver transplantation (OLT) in the treatment of Budd-Chiari syndrome in eight patients. Two patients (with hematologic diseases) died 2 weeks after the TIPS procedure. Median follow-up in the six survivors was 42.5 months (range, 11-79 mo). Multiple TIPS occlusions occurred in three patients (range, 2-7 revisions). Reocclusions occurred despite brachytherapy and Hemobahn stent-graft placement and necessitated OLT in one patient. Revision-free patency was achieved in the other two patients after VIATORR stent-graft placement (16 and 32 months after TIPS creation). All patients with stable TIPS (n = 5) are without ascites, no liver failure occurred, and no patients are currently on the transplant list.

Inborn errors presenting with liver dysfunction

In neonates, inborn errors of metabolism can produce all the major signs of liver dysfunction - jaundice, coagulopathy, hepatomegaly, splenomegaly, ascites and encephalopathy. The significance of encephalopathy in the neonate is different from that in older patients; it is usually due to a specific abnormality such as hypoglycaemia rather than being a non-specific indicator of liver failure. Attention is focused on five neonatal presentations: unconjugated hyperbilirubinaemia, cholestatic jaundice with otherwise good liver function, severe liver dysfunction (jaundice, coagulopathy persisting after vitamin K, and ascites), hepatomegaly with hypotonia+/- cardiomyopathy; and hepatosplenomegaly. The metabolic disorders presenting in these ways are listed alongside specific clinical features that can aid differential diagnosis and tests that can be used to confirm or refute the diagnosis. Diagnosis is important because treatment can be dramatically effective, e.g. withdrawal of galactose in galactosaemia. Even when treatment is not effective it is often possible to offer prenatal diagnosis for future pregnancies.

Mechanisms of liver injury relevant to pediatric hepatology

Hepatocyte injury and necrosis from many causes may result in pediatric liver disease. Influenced by other cell types in the liver, by its unique vascular arrangements, by lobular zonation, and by contributory effects of sepsis, reactive oxygen species and disordered hepatic architecture, the hepatocyte is prone to injury from exogenous toxins, from inborn errors of metabolism, from hepatotrophic viruses, and from immune mechanisms. Experimental studies on cultured hepatocytes or animal models must be interpreted with caution. Having discussed general concepts, this review describes immune mechanisms of liver injury, as seen in autoimmune hepatitis, hepatitis B and C infection, the anticonvulsant hypersensitivity syndrome, and autoimmune polyendocrinopathy. Of the monogenic disorders causing significant liver injury in childhood, alpha-1 antitrypsin deficiency and Niemann-Pick C disease demonstrate the effect of endoplasmic or endosomal retention of macromolecules. Tyrosinemia illustrates how understanding the biochemical defect leads to understanding cell injury, extrahepatic porphyric effects, oncogenesis, pharmacological intervention, and possible stem cell therapy. Pathogenesis of cirrhosis in galactosemia remains incompletely understood. In hereditary fructose intolerance, phosphate sequestration causes ATP depletion. Recent information about mitochondrial disease, NASH, disorders of glycosylation, Wilson's disease, and the progressive familial intrahepatic cholestases is discussed.

Congenital disorders of glycosylation

Congenital disorders of glycosylation (CDG) are a rapidly growing group of genetic diseases that are due to defects in the synthesis of glycans and in the attachment of glycans to other compounds. Most CDG are multisystem diseases that include severe brain involvement. The CDG causing sialic acid deficiency of N-glycans can be diagnosed by isoelectrofocusing of serum sialotransferrins. An efficient treatment, namely oral D-mannose, is available for only one CDG (CDG-Ib). In many patients with CDG, the basic defect is unknown (CDG-x). Glycan structural analysis, yeast genetics, and knockout animal models are essential tools in the elucidation of novel CDG. Eleven primary genetic glycosylation diseases have been discovered and their basic defects identified: six in the N-glycan assembly, three in the N-glycan processing, and two in the O-glycan (glycosaminoglycan) assembly. This review summarizes their clinical, biochemical, and genetic characteristics and speculates on further developments in this field.

Congenital disorders of glycosylation: the rapidly growing tip of the iceberg

In addition to many other organs, the brain is affected in 10 of the 11 known congenital disorders of N-linked glycosylation, mostly to a severe degree. Because a large number of enzymes, transporters and other proteins are involved in glycosylation (both N-linked and O-linked), it is expected that the great majority of congenital disorders of glycosylation (CDG) are yet to be identified. Many neurological patients with a CDG escape diagnosis for that reason, but also because existing screening methods fail to detect all patients with a known CDG. These disorders should be looked for in any patient, regardless of age, with an unexplained neurological disorder.