As shown in Tables 1 and 13 subjects of Chinese ancestry were enrolled, including 11 males and two females. The age of onset ranged between ten months and 17 years, with an average of 10.0 ± 5.5 years old. 12 cases were APOE-ε4 non-carriers, and one was ε4ε4 genotype. The elder brother of Case 1 was diagnosed with adrenoleukodystrophy at eight and died at 10. As for the other 12 subjects, no similar clinical manifestations were shown among their first-degree or second-degree family members (Table 2).

18 variants were found, including the ABCD1 (n = 4), EIF2B3 (n = 2), EIF2B4 (n = 2), EIF2B5 (n = 2), ARSA (n = 2), GFAP (n = 1), NDUFS1 (n = 2) and MPV17 variants (n = 3) (Table 3).

According to the ACMG criteria, there were eight pathogenic or likely pathogenic variants. Of them, the ABCD1 Q472fs, Y174D, G266R and GFAP R416W were reported before [8,9,10,11]. The EIF2B3 A151fs, EIF2B4 c.885 + 2T > G, EIF2B5 R129X and MPV17 Q142X were novel. The other ten missense variants were variants of uncertain significance (VUS). Of them, the EIF2B3 E44K, EIF2B4 R446H and MPV17 K88M were reported before [12,13,14]. The ABCD1 G343D, EIF2B5 R211S, ARSA P150S, G81D, NDUFS1 V89E, I537L and MPV17 M89L were novel.

Four male subjects harbored the ABCD1 variants. They all had elevated VLCFA. Three of them were accompanied by adrenocortical insufficiency. Brain MRI mainly showed bilateral posterior white matter hyperintensities (WMH) (Fig. 1).

The Q472fs carrier presented with visual and linguistic impairment at 10. He could speak fluently, but had difficulty in oral comprehension. The Y174D carrier started with difficulty in oral comprehension at 13. Gradually he presented with ataxia, memory deficit and visuospatial impairment. The G266R carrier showed intellectual impairment at 10. Gradually he exhibited ataxia, spastic paraplegia, dysarthria, visual and auditory impairment. He was bedridden at 13. The G343D carrier started with intellectual impairment at 12. Afterwards, he developed ataxia, spastic paraplegia and visual impairment. His serum cortisol and ACTH were normal.

Sanger sequencing and Brain MRI examples. (A-1) Sanger sequencing showed ABCD1 c.1028G > A (p.G343D) in Case 4. (A-2/3) Sanger sequencing showed EIF2B5 c.C385T (p.R129X) and c.G633T (p.R211S) in Case 7. (A-4) Sanger sequencing showed GFAP c.1246 C > T (p.R416W) in Case 9. (A-5/6) Sanger sequencing showed ARSA c.242G > A (p.G81D) and c.448 C > T (p.P150S) in Case 8. (B-1) Brain MRI showed bilateral WMH in tempro-parieto-occipital region and splenium of corpus callosum in Case 4. (B-2) Brain MRI showed bilateral diffuse WMH in the centrum semiovale, corona radiata, middle cerebellar peduncles with cystic degeneration in Case 6. (B-3) Brain MRI showed bilateral diffuse WMH in the centrum semiovale, corona radiata, corpus callosum, middle cerebellar peduncles in Case 10. (B-4) Brain MRI showed bilateral diffuse WMH in the periventricular area in Case 9. (B-5) Brain MRI showed bilateral T2/DWI hyperintensities in the centrum semiovale, corona radiata, splenium of corpus callosum with stripe-like pattern in Case 8. (B-6) Brain MRI showed diffuse T2/DWI hyperintensities in the subcortical regions, and T1 hyperintensities in the periventricular areas in Case 11

Three subjects harbored the EIF2B variants. They all had normal serum VLCFA, homocysteine (HCY), folic acid, vitamin B12 and organic acids. The brain MRI mainly indicated bilateral WMH in the centrum semiovale and corona radiata (Fig. 1). Two subjects had coexisting cystic degeneration.

The EIF2B3 E44K (paternal origin) and A151fs (maternal origin) were found in a 17-year-old male. He presented with intellectual impairment and dysuria after a syncope at 16. The EIF2B4 R446H (maternal origin) and c.885 + 2T > G (de novo) were in a 29-year-old male. He presented with progressive ataxia since seven. He could run and climb, but fell frequently. After an accidental trauma at 28, he showed unsteadiness while standing. Gradually, he developed memory deficit, disorientation, dyscalculia, delusion, spastic tetraplegia and dysuria. The EIF2B5 R211S (paternal origin) and R129X (de novo) were detected in a 22-year-old female. She started with seizure attack at 12. Gradually, she showed poor academic performance at school, accompanied by spastic tetraplegia, dysarthria and dysuria. At 20, she could not vocalize, eat or move.

Four subjects carried the variants in the ARSA, GFAP, NDUFS1 and MPV17. They had normal serum VLCFA, HCY, folic acid, vitamin B12 and organic acids.

The ARSA P150S (paternal origin) and G81D (maternal origin) were found in a two-year-old boy. At the age of one, he was able to walk and call mom, dad. Four months later, he showed gait instability and dysarthria. Gradually he could not speak, eat or move. Physical examination indicated spastic tetraplegia. Brain MRI showed bilateral diffuse WMH in the centrum semiovale, corona radiata, splenium of corpus callosum with stripe-like pattern (Fig. 1). Serum enzyme test showed decreased Arylsulfatase A level (3nmol/17 h/mgPr).

The de novo GFAP R416W was in a 28-year-old male. He showed cognitive decline since 17. Physical examination indicated bilateral Babinski sign with normal muscle force. Brain MRI revealed bilateral diffuse WMH in the periventricular area (Fig. 1).

The NDUFS1 V89E and I537L were in a 13-year-old boy. He was able to walk at three. He showed poor intelligence and seizure attack in early childhood. Brain MRI indicated bilateral diffuse WMH in the centrum semiovale, corona radiata, corpus callosum and middle cerebellar peduncles (Fig. 1).

The MPV17 Q142X, M89L and K88M were in a 15-year-old boy. He showed poor academic performance at 12. Two years later, he developed limb weakness and gait instability. Physical examination exhibited bilateral Babinski sign, decreased muscle force and tendon reflex in the extremities, as well as reduced pin-prick sensation in the distal extremities. Electromyography revealed peripheral neuropathy. Brain MRI demonstrated T2/DWI hyperintensities in the subcortical regions, cerebellum, and T1 hyperintensities in the periventricular areas (Fig. 1).