ASN

1
Congenital Disorders of Glycosylation
Thoughts on Clinical Care
Donna Krasnewich M.D., Ph.D. National Institutes
of Health Phone [phone]
ASN
2
CDG A Difficult Clinical Diagnosis
Hematology
Neurology
CDG
Genetics
Pediatrics
3
CDG A Multisystemic Disorder
Gastroenterology
Ophthalmology
Hematology
CDG
Rehab
Genetics
Cardiology
Pediatrics
Neurology
Endocrinology
4
CDG Multiple typesdifferent children and adults
Gastroenterology
Ophthalmology
Hematology
Rehab
Genetics
Cardiology
Pediatrics
Neurology
Endocrinology
5
CDG A Multisystemic Disorder
Gastroenterology
Ophthalmology
Hematology
CDG
Rehab
Genetics
Cardiology
Pediatrics
Neurology
Endocrinology
Lets use CDG-Ia as an example..
6
Presentation of CDG -Ia to the pediatrician
Children had developmental delay documented by
4-6 months of age
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CDG A Multisystemic Disorder
Gastroenterology
Ophthalmology
Hematology
CDG
Rehab
Genetics
Cardiology
Pediatrics
Neurology
Endocrinology
8
Gastrointestinal manifestations of CDG-Ia

• Feeding and Growth
• growth failure is universal and symmetric
  involving length, weight and head circumference
• infants are difficult feeders with persistent
  vomiting in the first year of life
• children may require G-tube placement for severe
  failure to thrive

9
Gastrointestinal manifestations of CDG-Ia

• Feeding and Growth
• Many children are on elemental formulas
• Many children are treated for gastroesophogeal
  reflux
• Some children had Nissen fundoplications with
  G-tube placement
• anecdotally, enrichment with MCT oil and high
  caloric formulas do not improve growth

10
Gastrointestinal manifestations of CDG-1A

• Hepatopathy-Liver problems
• all children had elevated transaminases in
  infancy
• 80 normalized by 2 years of age and remain
  normal, all normalized by 5 years
• 60 had hypoalbuminemia (low albumin) in infancy

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CDG A Multisystemic Disorder
Gastroenterology
Ophthalmology
Hematology
CDG
Rehab
Genetics
Cardiology
Pediatrics
Neurology
Endocrinology
12
Cardiac manifestations of CDG-Ia

• Pericardial Effusion
• Some children had documented pericardial effusion
  without clinical problems

13
CDG A Multisystemic Disorder
Gastroenterology
Ophthalmology
Hematology
CDG
Rehab
Genetics
Cardiology
Pediatrics
Neurology
Endocrinology
14
Neurologic manifestations of CDG-1A

• Axial and truncal low tone is seen in infancy

15
Neurologic manifestations of CDG-1A

• Seizures Stroke-like Episodes
• Some children have seizures
• All responded to anticonvulsants medications
  were tapered when children were seizure free for
  two years
• Some children have stroke-like episodes with the
  youngest at 3 years of age all had full
  functional recovery

16
Neurologic manifestations of CDG-Ia

• Many children have cerebellar hypoplasia on MRI

17
Neurologic manifestations of CDG-Ia

• Development
• All children continue to gain skills
• Many use walkers with truncal support
• All communicate with sign, dysarthric speech or
  communication boards
• All are happy, engaging children
• All are enrolled in early intervention or school
  programs for children with disabilities

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CDG A Multisystemic Disorder
Gastroenterology
Ophthalmology
Hematology
CDG
Rehab
Genetics
Cardiology
Pediatrics
Neurology
Endocrinology
19
Hematologic manifestations of CDG-Ia

• Coagulopathy
• All children had decreased levels of factors IX
  and XI
• Deficiencies of protein C and S are documented
• Children have tolerated surgery well but their
  physicians must be aware of the risks and
  precautions taken

20
CDG A Multisystemic Disorder
Gastroenterology
Ophthalmology
Hematology
CDG
Rehab
Genetics
Cardiology
Pediatrics
Neurology
Endocrinology
21
Endocrinologic manifestations of CDG-Ia

• 70 of children with CDG-1A have hypothyroidism
• Adult females with CDG-1A do not undergo
  pubescence
• Adult males with CDG-1A reach pubescence but have
  small testes

22
CDG A Multisystemic Disorder
Gastroenterology
Ophthalmology
Hematology
CDG
Rehab
Genetics
Cardiology
Pediatrics
Neurology
Endocrinology
23
Ophthalmologic manifestations of CDG-Ia

• All children have esotropia
• Retinitis pigmentosa is seen
• Individuals with CDG have myopia (near
  sightedness)

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Clinical features of American adults with CDG-Ia

• Ataxia, dysmetria, peripheral neuropathy,
• Muscle bulk ranges from normal to severely
  atrophic
• Retinitis pigmentosa
• Progressive contractures, kyposis, scoliosis,
  thoracic shortening

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Clinical features of American adults with CDG-Ia

• Hypothyroidism, female non-pubescent, males have
  small testes
• Dysarthric (slurred speech), interesting
  conversations, working in group work sites,
  living at home or in assisted settings

26
Clinical features of CDG-Ib

• Children present with failure to thrive,
  hypoglycemia (low blood sugar) and malabsorptive
  diarrhea
• The children are developmentally normal

27
Diagnosis of CDG
The diagnosis of CDG is initially based on a
clinical suspicion.
If abnormal transferrin patterns are seen, the
diagnosis is CDG
CDG typing is based on enzyme analysis of
fibroblasts or lymphs
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Issues in Infancy-CDG

• Medical Issues include
• Failure to thrive
• Oral motor dysfunction with persistent vomiting
• Abnormal liver function, coagulopathy and the
  infantile catastrophic phase
• Strabismus
• Pericardial effusion
• Hypothyroidism

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Issues in Infancy-CDG

• Developmental Delay
• May not be noted by parents or pediatrician until
  3-4 months of age
• Early intervention with speech, occupational and
  physical therapy is essential

30
Management and Counseling Issues in Childhood-CDG

• Liver dysfunction and eating issues improve
• Mobility improves
• Development progresses
• The rigors of physical, occupational and speech
  therapy continue
• Children enter school

• Seizures and stroke-like episodes may begin

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Management and Counseling Issues in
Adolescents-CDG 1a

• Continued seizures and stroke-like episodes
• Pubescence
• Development continues
• Transition to middle and high school system
• Increasing need of independence and self care
• Friends are funbut where do we find them?

32
Management and Counseling Issues in Adults-CDG 1a

• Joint immobility and progressive scoliosis lead
  to pain and mobilization difficulties
• Few seizures, medically stable
• Vocational goals and care issues take center
  stage
• Where do they work?
• Where do they live?
• How do they spend their time?
• How do their parents prepare for the future care
  of an adult with special needs?

33
Treatment strategies

• Mannose therapy for CDG-Ib has been clinically
  successful
• In general no other sugar therapy has been found
  to be therapeutic in other types of CDG

34
Genetics

• All of us have 46 chromosomes (23 pairs, 1 in
  each pair from our mother and one from our father
• These chromosomes are long strings of genes that
  are the blueprint for how we look, our health and
  even our behavior
• We carry about 30,000 genes, each of us carry
  5-10 changed genes
• In the random event that we conceive a child with
  another person with the same changed gene we have
  a 1 in 4 risk of having an affected child

35
Genetics of CDG

• All known types of CDG are inherited in a
  recessive manner

• Non-carrier

• Carrier CDG

• Carrier CDG

• CDG

• The risk of having another affected child is 1 in
  4 with each pregnancy

36
Prenatal diagnosis

• Prenatal diagnosis is available for some types of
  CDG in families where the mutation is known.
  Prenatal diagnosis is done in CDG-Ia with both
  enzyme analysis and mutational analysis of PMM-2.
  That is not true for other types.
• Amniocentesis and CVS can be used for prenatal
  diagnosis.

37
CDG Family Network

• The American and European families of children
  and adults have established a web based network
  and communicate freely about their experiences
  and feelings

38
Conclusions

• There is a broad spectrum of clinical
  manifestations seen in patients with CDG. This
  heterogeneity is like that reported for other
  single gene disorders but still defies
  explanation.
• CDG is underdiagnosed in the United States,
  physician education will contribute to its
  recognition.

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CDG Clinical Consensus Meeting during the 2nd
International Meeting on CGD April 2, 2003
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Objective

• This 2-3 hour session was conceived to bring
  together physicians, with expertise in caring for
  children and adults with CDG, to discuss
  specific medical management issues.
• Obviously, not all medical issues can be
  covered. Strategies and anecdotes will be shared
  and ideally, a brief synopsis statement will be
  given at the end of the International Conference.
  
• Eventually, a jointly written document will
  summarize the management experience of the
  experts involved.
• These discussions will also elucidate areas where
  clinical research is needed in CDG.

41
Participants

• At the round table
• Jaek Jaeken(Belgium) Pascal de Lonlay(France)
• Stephanie Grunewald(Germany) Brian Winchester(UK)
• Chris Hendriksz(UK) Thorsten Marquardt(Germany)
• Hudson Freeze(US) Agata Fiumara(Italy)
• With expert input from Flemming
  Skovby(Denmark)
• Peter Clayton(UK)
• Rita Barones(Italy)
• Editorial Group now includes Paz
  Briones(Spain), Susanne Kjaergaard(Denmark),
  Dusica Babovic(US), Eva Morava(Netherlands),
  Dulce Quelhas(Portugal)

42
Question

• Is the transferrin IEF always abnormal in child
  affected with CDG-1a?
• Does the transferrin IEF always stay abnormal in
  a child affected with CDG-1a?

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Consensus

• Several in the group reported that when
  transferrin was normal but the clinical suspicion
  was strong, PMM activity was analyzed as a
  backup..
• There are 2 cases where transferrin IEF in a PMM
  deficient child was abnormal and became normal,
  for 3 years in one case.

44
Consensus

• Consensus is that if transferrin IEF is normal
  but clinical suspicion is strong
• Check other proteins for evidence of abnormal
  glycosylation (ie. increased lysosomal enzymes in
  sera, abnormal alpha-1-antitrypsin IEF ..
• Do PMM assay on WBC pellet

45
Question
What is the appropriate management and
nomenclature of stroke-like episodes
46
Consensus

• Nomenclature We will continue to use the word
  stroke-like episodes. We may revisit this should
  there be documentation of a CNS thrombotic event.
• Management
• Anecdotal evidence in one case suggests that
  aspirin decreases the number of stroke-like
  episodes in an individual with monthly strokelike
  episodes.
• Not all children should be started on ASA.

47
Questions

• Should mannose therapy be given to CDG-1a
  patients?

48
Consensus

• The group consensus is that no child with CDG-1a
  should be started on mannose therapy at this
  time.
• This conclusion was based on no solid evidence in
  previous studies of improvement in biochemical
  parameters, clinical manifestations, growth or
  development.

49
Consensus

• However, there are 5 patients currently being
  followed on 1gm/kg/day divided qid some for
  several years.
• Parents of this group feel that the children are
  doing better.
• Clinical information from this group will either
  support or refute the usefulness of long term
  mannose therapy.
• No plans for another clinical trial of mannose at
  the time.

50
Question.

• How are the CDG-1b patients doing worldwide?
• What is the dosing of mannose therapy for
  patients with CDG-1b?
• Any toxicity noted from the mannose?

51
Consensus

• Dosing 100-200mg/kg/dose given 4 times daily
• Blood levels peak 100-200micromoles/L
• Diarrhea limits the amount given, so monitoring
  is by tolerance
• Clear phenotypic variability including
• the severely affected case, treated with mannose
  for 5 years with cirrhosis
• The 35 yo woman with 2 children not on mannose

52
Consensus

• Clinical concerns include
• Patients with CDG-1b are at risk for thrombosis.
• Long term toxicity of mannose not known(ie. All
  patients with CDG-1b have some fibrosis on
  initial liver biopsy, when do you do another???

• Propose
• Gather clinical experience

53
Question
Do children with CDG-1a have increased risk of
infections? Are these children responding to
vaccinations?
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Consensus

• It is important to react quickly when these
  children are sick even though there is no
  laboratory evidence of immunocompromise.
• Gather evidence of response to vaccines.

55
Question
What is the appropriate management of ostepenia
in patients with CDG-1a?
56
Consensus

• Although some patients with CDG-1a have multiple
  fractures it is not a common problem.
• Fractures seem to heal well
• Immobilization of these patients is an issue
  because of the risk of thrombosis
• No supplemental phosphorus is needed unless
  clinically indicated.

57
Question
Should we give estrogen replacement to women with
CDG-1a?
58
Consensus

• Estradiol is being started at 16 years of age in
  young women with CDG-1a.
• Group experience is 2 women are on estrodiol
  without problems

59
Other issues discussed..

• Cerebellar hypoplasia versus atrophy
• What is the best nutritional support?
• What is the best management of retinal dystrophy?
• What other CDGs are prenatal available and
  appropriate for??

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STAY TUNED FOR THE NEXT CHAPTER....
61
Diagnosis of CDG
Anode
Cathodally migrating bands
Cathode
Cathodally migrating bands on serum transferrin
isoelectric focusing are diagnostic for CDG
CDG
Controls
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N-linked oligosaccharides are complex structures
Composed of

• Monosaccharides
• Linked together in a specific structural pattern
• Synthesis is highly regulated

ASN
-asparigine
-mannose
-glucose
-NANA
-GlcNAc
-galactose
63
N-linked oligosaccharides are complex structures
Localized on

• Cell surfaces
• Extracellular matrix
• Secreted proteins

ASN
-asparigine
-mannose
-glucose
-NANA
-GlcNAc
-galactose
64
The function of N-linked oligosaccharides
N-linked oligosaccharides are involved in

• Proper protein folding
• Protease resistance
• Intracellular trafficking
• Cell-cell interactions

65

• Synthesis begins on a dolichol backbone
• Each sugar is added by a sugar specific and
  linkage specific glycosyltransferase
• Dol-linked oligosaccharides are transferred from
  cytoplasm to the ER lumen during synthesis

DOL
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ER lumen
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Phenotypic heterogeneity is expected in CDG

• Because the pathway has about 200 steps
• A defect in any one step may lead to the clinical
  manifestations of a novel CDG type

68
CDG typing

• Each CDG type is the phenotype defined by a
  specific enzyme defect and the mutation in its
  underlying gene
• There are now 7 known types of CDG

69
ER lumen
N-linked oligosaccharide synthetic pathway
ER membrane
Cytoplasm
DOL
2a
1c
DOL
ASN
P
ASN
-asparigine
-mannose
-glucose
-NANA
-dolichol
-GlcNAc
-galactose
DOL
1e
Gene
CDG Types
Enzyme
P
1d
PMM2 PMI Alg6 Alg3 DPM1 MATII
1a 1b 1c 1d 1e 2a
phosphomannomutase phosphomannose isomerase a 1,3
glucosyl transferase dolichol-P-mannose
transferase dolichol-P-mannose synthase N-acetylgl
ucosamine transferase II
DOL
Fructose-6-P