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CLINICAL SYMPTOMS AND GENETIC
ANALYSIS OF CERTAIN MUCOPOLYSACCHARIDE
DISEASES - IVA TYPE IN VIET NAM
Le Thi Thuy Hang1, Vu Chi Dung2, Tran Van Duy1
Can Thi Bich Ngoc2, Nguyen Le Thanh Thu1
1Military Hospital 103, Military Medical University
2Central Children's Hospital
ABSTRACT
Background: Mucopolysaccharide IVA is a rare recessive genetic disease resulting from a deficiency of
N 6 sulfatase acetylgalactosamine (galactose 6 sulfatase) - a lysosome’s enzyme necessary to degrade
keratan sulfate and chondroitin sulfate. Objectives: To describe clinical characteristics and genetic analysis
of 13 children with MPS IVA in National Pediatric Hospital. Subjects and methods: 13 patients with MPS
IVA were diagnosed based on analysis of clinical data and enzyme activity. Five were analyzed for the gene.
Results: ligament manifestation accounted for 100%, sternal deformation - 92.3%, dwarf - 61.5%, hearing loss
- 58.3%, mild mental retardation - 38.5%, heart valve lesions, cornea opaque - 30.8%, rough face - 15.4%,
hepatomegaly - 7.7%. 5 mutations were detected: p.V427SfsX14, p.P125L, p.Y385X, p.A291T, c.899-2A> C.
Conclusion: Ligament laxity and bone deformity, especially sternal deformation, are highly valuable for
diagnosing MPS type IVA. The discovery of genotypes will help doctors in giving genetic advice to families.
* Keywords: Mucopolysaccharide (MPS); Glycosaminoglycans (GAGs).
INTRODUCTION
Mucopolysaccharide IVA (MPS IVA) is an autosomal
recessive genetic disease resulting from a deficiency
of N-acetylgalactosamine-6-sulfate sulfatase
(GALNS) - a lysosome’s enzyme necessary to
degrade keratan sulfate and chondroitin sulfate.
The live birth incidence of MPS IVA is 0.15/100,000
[1]. In patients with manifestations including
short stature, capitellum, and cartilage (skeletal)
dysplasia, corneal accumulation, most patients
have normal mental development.
The main clinical manifestations of Morquio
syndrome are bone-related features and their
effects on the central nervous system. Most
patients have a regular appearance at birth. Then
they begin to develop symptoms including venu
valgum, kyphosis/gibbus, growth retardation, short
stature, short neck, abnormal gait, easy to stumble,
etc. that are early symptoms of Morquio syndrome.
Typical skeletal abnormalities of Morquio syndrome
include short stature, dwarf, vertebra plana,
odontoid hypoplasia, spinal abnormalities, cervical
instability, vertebra ovarian deformity, pectus
deformity, venu valgum, deformed ulna, elbow
deformity, deformed metacarpus, short phalanges,
capitulum deformity, osteoporosis.
The loose ligament is a characteristic symptom
of Moriquio syndrome. Manifestations of spinal
Corresponding author: Le Thi Thuy Hang
Date received: 28/4/2021
Date accepted: 27/5/2021
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cord paralysis, limited chest movement, and heart
valve disease lead to premature death. Severely
affected patients cannot live beyond twenty or
thirty years old. Cervical spine stabilization surgery
can prolong life.
Other manifestations of Moriquio syndrome
are mild corneal opaque, hepatomegaly, upper
airway obstruction, valvular lesions, small teeth,
abnormally thin enamel, and frequent cavities,
rough face, possibly deaf [2, 3].
Patients with MPS IVA usually present 3 levels:
Severe (manifestation of skeletal dysplasia
appears before 1 year of age, the disease is
usually diagnosed before age 5, maximum height
is less than 120cm). Mild (manifestation of skeletal
dysplasia appears in late teens, the maximum
height of more than 140cm). Moderate (bone
dysplasia manifestation appears in childhood, the
maximum height reaches 120 - 140cm) [2, 3].
Treatment of MPS IVA in the world today includes
alternative enzyme therapy, medical treatment with
Bisphosphonate, tooth protection, and orthopedic,
spinal orthopedic surgery, especially neck and
waist to avoid compression and prolong service
life. Surgical treatment of patients with MPS IVA
pays attention to chiropractic treatment; Early
rehabilitation also contributes to improved disease
progression [2], [3]. The treatment will be effective
if the disease is diagnosed early. Patients with
MPS IVA are often diagnosed late. Based on these
practical requirements, we conducted this research
with the following objectives: Description of clinical
and subclinical symptoms for 13 patients with MPS
IVA, of which 5 patients were genetically analyzed.
SUBJECTS AND METHODS
1. Subjects
13 patients were diagnosed with MPS IVA at the
Endocrinology Department of National Hospital of
Pediatrics from September 2013 to October 2015.
Patients were selected based on criteria set by
Thomas J. A. Lehman et al. 2011 [4, 5] as follows:
* Clinical standards:
Patients with one or more of the following suspected
MPS symptoms: Mental retardation, impaired
memory, possible hyperactivity, Rough face (Big
head, big forehead, flat nose, big nose, big lips,
big tongue), osteoarthritis deformity, joint stiffness
or loose ligaments, Umbilical or inguinal hernia,
short stature, liver and/or splenomegaly, Hearing
loss and deaf, cloudy cornea, heart valve damage-
causing heart failure, family history (sibling of MPS
patient).
* Laboratory standards:
Blood samples will be centrifuged to separate
leukocytes, then incubated with a specific substrate
required by the process and read the results on a
spectrofluorometer. Enzyme activity in peripheral
blood lymphocytes decreased (required standard
when gene analysis results are not available). The
conclusion is an enzyme deficiency occurs when
enzyme activity is <10% compared to normal, the
total Glycosaminoglycan in urine increases.
2. Methods
This is a descriptive clinical study with a utility
sample size. The patients were examined
clinically, exploited for family genealogy, subject
to functional evaluation tests performed at the
National Hospital of Pediatrics, measured for the
activity of enzymes at laboratories specialized in
Asian lysosome disease - the hospital of National
Taiwan University. Extraction of DNA from
peripheral blood lymphocytes was performed at
the Genetics and Molecular Biology Section of
the National Hospital of Pediatrics. DNA samples
were sent to the Genetics Laboratory of Aasn
Medical Genetics Centre, Seoul City, South Korea.
PCR amplified all exon and exon-intron binding
sites of these genes. PCR products were purified
and sequenced directly by the Sanger method.
The sequencing reaction was analyzed on ABI
Prism 3730 DNA automatic sequencer (Applied
Biosystems, Warrington, UK) and compared with
the published gene sequence.
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The subjects were approved by the National
Hospital of Pediatric Ethics Council (date of
approval: February 21, 2012), with the consent of
the patients’ parents, ensuring the confidentiality of
the study subjects.
RESULTS
Age of onset of symptoms and age of diagnosis:
Age of onset of symptoms from patients right after
birth to 3 years (1.0 ± 0.8) and age of diagnosis of
patients from 1.3 - 7.5 years old (3.9 ± 1.9). Out
of 13 patients (9 men and 4 women), 12 patients
have the first symptoms of bone deformation. 1
patient is mentally disabled.
1. Clinical symptoms of MPS IV patients
Table 1: Clinical symptoms
of 13 MPS IV patients.
Symptoms Number of
patients
Ratio
(%)
Loose ligament 13/13 100
Bone deformation 12/13 92.3
Sternum deformation 12/13 92.3
Short stature 8/13 61.5
Hearing loss 7/12 58.3
Mental retardation 5/13 38.5
Cloudy cornea 4/13 30.8
Damage to the heart
valve 4/13 30.8
Having a family history 3/13 23.1
Rough face 2/13 15.4
Large liver 1/13 7.7
Joint stiffness 0/13 0.0
Inguinal or umbilical
hernia 0/13 0.0
Loose ligaments, bone deformities, sternal
deformities are symptoms that account for a
high proportion of MPS IVA patients. Followed by
dwarfism, hearing loss.
Photos of patients with MPS IVA in the research:
(A) 2-year and 7-month-old patient;
(B) 7 years and 7 months - old patient
(C) 3-year-old patient 3 months;
(D) Patient 6 years and 10 months old
Figure 1: Photos of patients with MPS IVA in the
research (A, B, C, D).
Patients with multiple bone deformities, including
severe chest deformity, the emerged breastbone,
extremely loose ligaments (back of the hand can
be close to the back of the forearm).
2. X-ray bone damage in 13 patients with MPS IV
Table 2: X-ray bone damage in 13 patients
with MPS IV.
Bone damage on X-rays MPS I
Spinal deformities, vertebral injuries 11/13
Decreased height of vertebra’s body 8/11
Oar shaped ribs 10/13
Long bones deformation 10/13
Spinal cervical cord compression 8/8
Brain cranial lesion was detected by
MRI scanning 2/10
Osteoporosis 6/13
(A)
(B)
(C)
(D)
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Images of neck marrow compression, spinal deformities, vertebral lesions with the highest rate, followed
by paddle ribs and long bone deformities.
Figure 2: Bone lesions on X-ray of patients with MPS IVA.
3. Galactose 6-sulphatase enzyme activity
Galactose 6-sulphatase enzyme activity (In leukocytes) of 13 patients with MPS IVA: 0.74 nmol/mg
Prot/17hrs (ranges from 0.01 to 66.24 and average is 11.38 ± 22.18). Normal values are 158.9 ± 82.8
nmol/mg Prot/17hrs.
4. GALNS mutations in 5 patients with objective MPS IV
Table 3: Genotype and clinical manifestations of patients with MPS IVA.
Item c.DNA Protein
Enzyme activity
(nmol/mg
Prot/17hrs)
GAGs
mg/gram
creatinine
Clinical form
Patient Nr. 1 c.1279delG/
c.1279delG
p.V427SfsX14/p.
V427SfsX14 0.74 332.73 Severe
Patient Nr. 2 c.899-2A>C/
c.899-2A>C 0.67 193.38 Severe
Patient Nr. 3 c.374C>T/
c.1155C>G
p.P125L/p.
Y385X 0.09 269.68 Severe
Patient Nr. 4 c.1279delG/
c.1279delG
p.V427SfsX14/p.
V427SfsX14 0.01 320.25 Severe
Patient Nr. 5 c.871G>A p.A291T 0.02 291.44 Severe
There were 5 different pathogenic mutations of the GALNS gene detected in 5 patients with MPS IVA. In
which, p.V427SfsX14 the unpublished deletion mutation was detected in two homozygous patients. All 5
patients had a severe phenotype.
Family genealogy and genomic sequencing results of 1 patient with MPS IVA
Figure 3: Illustration of family genealogy and
results of gene sequencing of a patient with
MPS IVA No. 1, (2013).
Male (normal health group) Male (disease health group)
Female (normal health group) Studied patients
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In the family genealogy, there was no one
diseased like the patient. The unpublished small
deletion mutation c.1279delG was caused by loss
of nucleotide G at position 1279, leading the 427th
threesome GTC encoding Valine to be converted
into Serine coding TCA. The transcription process
has deviated and immaturely stopped after the
following 14 codes (p.V427SfsX14).
DISCUSSION
1. Clinical characteristics of 13 patients
In our study, the age at which the first symptoms
of MPS IV patients were relatively early ranged
from birth to 3 years, averaging 1.0 ± 0.8 years.
The diagnostic age of patients ranged from 1.3 to
7.5 years, an average of 3.9 ± 1.9 years. In this
group, early symptoms of patients are mainly bone
deformation (chest wall deformity, spinal deformity,
growth retardation).
CJ Hendriksz and colleagues studied 399 patients
with MPS IVA in 2011, the average age when
the first symptom appeared was 2.2 years, the
average diagnostic age was 4.9 years, and the
stage of 1-3 years had the highest diagnosis rate
(34%). The early symptoms in patients were short
stature (49.9%), venu valgum (45.1%), kyphosis/
gibbus (44.4%), protruding breastbone (43.6%),
abnormal gait (37.8%) [3].
The study of Hsiang Yu Lin et al. on 24 Taiwan
patients with MPS IVA in 2014 whose first
symptoms appeared at the age of 2 ± 1.6 years.
The diagnostic age was 5.7 ± 4.5 years. The early
onset symptoms of patients are usually kyphosis/
gibbus (92%) [6].
In our study, loose ligament symptoms accounted
for 100%. This expression is the first suggestion for
the clinical MPS IVA form. Bone deformity, sternum
deformation (pectus excavatum or carinatum)
accounted for 92.3%, and this is a very symptom
that makes family members anxious to take their
children to see doctors. Dwarf - 61.5%. Hearing
loss - 58.3%. Mild mental retardation - 38.5%.
Damage to the heart valves, corneal opaque -
30.8%. Having a family history - 23.1%. Rough
face - 15.4%. Hepatomegaly - 7.7%. None of the
patients had an inguinal or inguinal hernia (table 1).
In Hsiang Yu Lin’s study, the most common
symptoms in Taiwan patients with MPS IVA were
kyphosis/gibbus (100%), pectus carinatum (96%),
abnormal gait (93%), short stature and stunting
(92%), venu valgum (92%), cardiac injury in this
study was relatively high 91% [6].
In CJ Hendriksz’s study on 399 patients with MPS
IVA, the most common symptoms were dwarf
(84.7%), venu valgum (78.7%), pectus carinatum
(71.4%), gibbus (70.4%), abnormal gait (64.4%),
loose ligaments (63.2%) [3].
The clinical symptoms of patients with MPS IVA
summarized by Souhir Khedhiri et al. (2011),
Timothy C Wood et al. (2013) include loose
ligament of the wrist joint, bone deformity, pectus
excavatum or carinatum, gibbus, and dwarfism,
which are prominent symptoms suggesting the
diagnosis. In addition, the patients are also easy
to suffer from respiratory infections, possible
hearing loss, mild corneal opaque, inguinal or
umbilical hernia, heart valve injury, larger liver, or
splenomegaly. On the other hand, the face is not
rough and has slight mental retardation [5, 7].
2. Main subclinical characteristics of MPS patients
* X-ray images of 13 patients (Figure 2):
Most patients have bone deformities in which
spine deformity, vertebral lesions are encountered
with the highest rate, leading to spinal cervical cord
compression, followed by oar-shaped ribs, long
bone deformities, and osteoporosis with a lower
incidence rate. Very few patients have lesions on
cranial MRI film (Table 2).
Souhir Khedhiri et al. (2011) on X-ray images of
7 patients with MPS IVA shows 5 patients with
cervical vertebra compression [7].
According to CJ Hendriksz et al. (2013), Shaukat
khana et al. (2017), bone damage of patients with
MPS IVA often increased with manifestations of