FM DECEMBER 2018 ISSUE - digital edition

case reports
METABOLIC DEFECTS LEADING
TO BEHAVIOUR DISORDER
A type of mucopolysaccharidosis can be easily misdiagnosed as ADHD or autism
Lysosomal storage diseases are a group of inherited
metabolic disorders that occur as a consequence of a
deficiency in a single key enzyme required for either lipid,
glycoprotein or mucopolysaccharide metabolism, affecting
several organs. The key symptoms of lysosomal storage disease
include developmental delays, movement disorders, seizures
and/or even dementia, deafness or blindness. Some patients
have hepatomegaly or splenomegaly as well as pulmonary or
cardiac problems or bones that grow abnormally. The severity
and type of symptoms depend on the precise enzyme that is
deficient.
Dr. Kiran Kartheek Veeranki, a leading paediatrician
practising at Sravani Hospital at Guntur in Andhra Pradesh, was
presented with five-year-old Ravi (name changed), who was
showing behaviour abnormalities and delayed milestones. The
boy’s gross motor skills were limited to walking and climbing
stairs and his fine motor skills limited to drawing straight
lines. He was also delayed in speech and continued to have
stranger anxiety. His parents also complained of loose stools
and abdominal distention since the child was one year old.
On examination, Dr. Kiran observed that the child had coarse
facies, short stature, and hepatomegaly. Based on these clinical
observations, he suspected the child to have a lysosomal
storage disorder. Several primary tests were performed to
rule out liver problems and infections. Liver function tests like
total bilirubin, aspartate aminotransferase
and alanine aminotransferase were normal,
as were blood counts and stool culture. To
confirm the diagnosis and identify the type of
lysosomal storage disease, the child’s blood
sample was sent for genetic testing. Genetic
testing is critical in confirming the diagnosis,
which, in turn, dictates the treatment regimen.
The results showed that the patient had a
SANFILIPPO SYNDROME B IS
A TYPE OF RARE, AUTOSOMAL
RECESSIVE LYSOSOMAL
STORAGE DISEASE CAUSED
DUE TO A DEFICIENCY OF
GLYCOSAMINOGLYCAN
HEPARAN SULFATE
mutation in the NAGLU gene, which causes
mucopolysaccharidosis type IIIB, also known
as Sanfilippo syndrome B.
Sanfilippo syndrome B is a type of
rare, autosomal recessive lysosomal
storage disease caused due to a deficiency
in enzymes required to metabolise
glycosaminoglycan heparan sulfate.
Glycosaminoglycans are unbranched
polysaccharides that are attached
to proteoglycans in the extracellular
matrix and the cell membrane. Several
enzymes are important for metabolism
of glycosaminoglycan heparan sulfate
– heparin N-sulfatase, N-acetyl-alpha-
D-glucosaminidase, acetyl-CoA:alphaglucosaminide
N-acetyltransferase, and
N-acetylglucosamine-6-sulfatase. The NAGLU
gene encodes alpha-N-acetylglucosaminidase,
44 / FUTURE MEDICINE / DECEMBER 2018