Table 1 Clinical and laboratory findings of the study sample

Clinical picture at diagnosis

moderate mental retardation, severe language deficit withoral–motor dyspraxia, epilepsy, temper tantrums, clumsiness

mild mental retardation, language deficit

severe mental retardation, impairment in social interaction, epilepsy and language deficit

moderate mental retardation, epilepsy, language deficit

severe mental retardation, language deficit, epilepsy

Type of seizures

sporadic occipital seizures

two episods of febrile convulsions at 3 and 4 yrs

myoclonic seizures (2 yrs) asymmetrical spasms at 8.5 yrs

severe epilepsy with SE and polymorphic seizures (generalized, focal, myoclonic); followed by sporadic GTCS

secondarygeneralized FS at onset; apparently primary GTCS from 8 to 16 yrs

Urinary molar Cr to Crn ratio and Cr uptake*

Cr/Crn ratio: 2.35 (n.v. < 1.0) Cr uptake absent

Cr/Crn ratio: 3.08 (n.v. < 1.0) Cr up take absent

Cr/Crn ratio: 3.6 (n.v. 0.006-1.2) Cr uptake absent

Cr/Crn ratio:1.83 (n.v. 0.03-0.92) Cr uptake absent

Cr/Crn ratio: 2981  μmol Cr/mmol Crn(n.v. 22–1273) Cr uptake absent

SLC6A8 mutation

c. 1006–1008 del AAC (de novo)

c.757 G > C (inherited)

IVS1-2A > G (inherited)

c.1631 C > T (inherited)

c. 1006–1008 del AAC (inherited)

MRI

slight white matter hyperintensity in paratrigonal region

normal

white matter hyperintensity in the posterior regions

normal

white matter hyperintensity in the posterior regions

MRS

PCr/PDE

tCr

PCr/PDE

tCr

PCr/PDE

tCr

PCr/PDE

tCr

PCr/PDE

tCr

n.v.1.40  ± 0.07

n.v.4.37  ± 0.34

n.v.1.40  ± 0.07

n.v.4.37  ± 0.34

n.v.1.40  ± 0.07

n.v.4.37  ± 0.34

n.v.1.40  ± 0.07

n.v.4.37  ± 0.34

n.v.1.40  ± 0.07

n.v.4.37  ± 0.34

T0

0.16

0.65

0.78

2.01

0.86

0.3

-

-

-

-

T1

0.33

1.27

0.92

1.98

1.07

2.1

-

-

0.97

2.01

T2

0.58

1.88

#

#

#

#

0.98

2.97

0.95

1.7

T3

0.63

1.8

0.81

3.49

1.00

2.0

Age at Arg treatment onset, dosage and duration of follow-up

8 yrs, 6 mo 300 mg/kg bw/day per os24 mo

5 yrs, 5 mo300 mg/kg bw/day per os24 mo

8 yrs, 6 mo300 mg/kg bw/day per os24 mo

6 yrs, 5 mo300 mg/kg bw/day per os36mo

17 yrs300 mg/kg bw/day per os24 mo