dystonia. Brain magnetic resonance imaging (MRI) at
1 week of age suggested generalized delayed myelination.
EEG at 8 months of age demonstrated severe
epileptic cerebral dysfunction. Seizures ceased at the age
of 9 months, but the patient continued to vomit every
day. Her development was at best at 6 months of age,
when she started holding her head. She had regular
follow-up visits in India and was totally dependent on the
caregiver, but was not on any medications and had not
been hospitalized. The diagnosis was made at 4 years of
age when the family came to Thailand and she was
referred to our hospital. She presented with profound
mental retardation. Her head circumference was 45.5 cm
(j3 SD) and her weight was 14 kg (j1 SD). She had
hypertonia and hyperreflexia with positive clonus.
Neither dysmorphic features nor abnormal odour was
observed. Plasma amino acid analysis revealed increased
levels of branched-chain amino acids (1542 mmol/L for
leucine, 506 mmol/L for valine, and 376 mmol/L for
isoleucine). Urine organic acid analysis by gas chromatography–
mass spectrometry revealed a large amount of
2-hydroxyisovaleric acid. The clinical picture and the
greatly elevated BCAA concentrations in plasma indicated
that the patient suffered from a severe form of
MSUD. Treatment with a special formula was subsequently
started. She responded poorly to the treatment.
Her developmental status remained the same. She also
suffered from multiple episodes of pneumonia, and died
at the age of 7 years.
Mutation analysis by PCR-sequencing revealed a novel
homozygous mutation, c.529C>T, in exon 5 of the
BCKDHA gene (data not shown). The nucleotide change
was predicted to cause a truncating mutation (p.Q177X)
in the E1a subunit of the BCKA complex. Using
restriction fragment length polymorphism (RFLP) analysis,
it was confirmed that the index patient was
homozygous for the c.529C>T transition and both parents
were found to be carriers of the mutation (Fig. 1).
Identification of the disease-causing mutation enabled
us to give more accurate genetic counselling. One year