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Clinical and biochemical outcome after hydroxocobalamin dose escalation in a series of patients with cobalamin C deficiency.
[homocystinuria without methylmalonic aciduria]
CblC
deficiency
produces
a
combination
of
methylmalonic
aciduria
(
MMA
)
and
homocystinuria
(
HCU
)
,
and
is
the
most
common
error
of
cobalamin
metabolism
.
Patients
present
a
wide
spectrum
of
symptoms
,
ranging
from
early
severe
multisystemic
forms
,
to
milder
late-onset
phenotypes
.
Cognitive
and
visual
impairment
are
nearly
constant
.
Hydroxocobalamin
(
OHCbl
)
,
betaine
,
folinic
acid
,
levocarnitine
and
eventually
dietary
protein
restriction
are
the
main
therapeutic
approaches
.
Although
early
introduction
of
OHCbl
is
crucial
,
no
standardized
protocols
regarding
dose
adaptation
exist
.
No
reports
on
long
-term
outcomes
after
high
doses
of
this
vitamin
have
been
published
.
In
this
study
five
patients
with
CblC
deficiency
(
early
severe
forms
)
were
treated
with
high
doses
of
OHCbl
for
18
to
30
months
.
Clinical
examinations
,
neurological
assessment
,
and
biochemical
studies
(
plasma
total
homocysteine
(
tHcy
)
,
amino
acids
,
hydroxocobalamin
,
and
methylmalonic
acid
in
urine
)
were
periodically
performed
.
Variable
clinical
and
biochemical
outcomes
were
observed
in
patients
treated
with
high
doses
of
OHCbl
.
The
best
biochemical
response
was
observed
in
those
children
with
the
worse
metabolic
control
.
By
contrast
,
those
patients
with
a
concentration
of
tHcy
around
50
μmol
/
l
or
less
showed
only
minor
changes
.
Clinically
,
a
considerable
improvement
was
observed
in
those
patients
with
severe
problems
in
communication
,
expressive
language
and
behavior
.
According
to
our
study
,
high
OHCbl
doses
in
CblC
deficiency
could
have
a
greater
benefit
in
those
children
with
a
prior
history
of
suboptimal
metabolic
control
,
and
also
in
those
with
severe
neurological
phenotypes
.
More
specifically
,
we
observed
improvements
in
communication
skills
and
behavior
.
These
results
should
encourage
further
prospective
trials
to
determine
the
optimal
OHCbl
regimen
and
to
generate
protocols
and
guidelines
in
this
rare
disorder
.
Diseases
Validation
Diseases presenting
"visual impairment"
symptom
adrenomyeloneuropathy
alexander disease
aniridia
coats disease
cohen syndrome
congenital toxoplasmosis
hirschsprung disease
homocystinuria without methylmalonic aciduria
hydrocephalus with stenosis of the aqueduct of sylvius
neonatal adrenoleukodystrophy
oculocutaneous albinism
werner syndrome
This symptom has already been validated