Clinical characteristics and whole-body MRI findings of the patients
WBMRI was performed on 70 children with NF1 (41 girls and 29 boys) at the mean age of 1.6 ± 0.7 years. The cohort included 14 familial cases, 53 sporadic cases and 3 patients with unknown inheritance patients. The clinical and radiologic characteristics of these patients are shown in Table 1.
Table 1
Baseline clinical and radiological findings of NF1 patients younger than 3 years old.
|
|
0–1 year (N = 8)
|
1–2 years (N = 45)
|
2–3 years (N = 17)
|
p value
|
|
Gender
|
Male
|
3/8 (37.5%)
|
15/45 (33.3%)
|
11/17 (64.7%)
|
0.087
|
|
Inheritance
|
Familial
|
0 (0.0%)
|
7/45(15.6%)
|
7/17 (41.2%)
|
0.011
|
|
|
Sporadic
|
6/8 (75.0%)
|
37/45 (82.2%)
|
10/17 (58.8%)
|
|
|
|
Unknown
|
2/8 (25.0%)
|
1/45 (2.2%)
|
0/17 (0.0%)
|
|
|
Clinical findings
|
|
|
|
|
|
|
Café-au lait macules
|
8/8 (100%)
|
45/45 (100%)
|
17/17 (100%)
|
–
|
|
|
Axillary freckling
|
2/5 (40.0%)
|
14/42 (33.3%)
|
12/15 (80.0%)
|
0.005
|
|
|
Cutaneous neurofibromas
|
1/5 (20.0%)
|
4/23 (17.4%)
|
2/12 (16.7%)
|
1.000
|
|
|
Relative macrocephaly
|
2/8 (25.0%)
|
22/42 (52.4%)
|
13/17 (76.5%)
|
0.052
|
|
|
Lisch nodules
|
0/2 (0.0%)
|
3/10 (30.0%)
|
5/13 (38.5%)
|
0.205
|
|
|
Short stature
|
0/8 (0.0%)
|
1/45 (2.2%)
|
1/17 (5.9%)
|
0.590
|
|
|
Developmental delay
|
0/4 (0.0%)
|
2/26 (7.7%)
|
2/12 (16.7%)
|
0.721
|
|
|
Seizure
|
1/3 (33.3%)
|
1/26 (3.8%)
|
0/9 (0.0%)
|
0.205
|
|
|
Cardiac anomaly
|
1/2 (50.0%)
|
1/8 (12.5%)
|
–
|
0.378
|
|
|
Hearing defect
|
–
|
0/12 (0.0%)
|
0/6 (0.0%)
|
–
|
|
Radiologic findings
|
|
|
|
|
|
|
FASI
|
6/8 (75.0%)
|
26/45 (57.8%)
|
15/17 (88.2%)
|
0.056
|
|
|
Optic pathway glioma
|
0/8 (0.0%)
|
4/45 (8.9%)
|
7/17 (41.2%)
|
0.006
|
|
|
Moyamoya disease
|
0/8 (0.0%)
|
1/45 (2.2%)
|
0/17 (0.0%)
|
1.000
|
|
|
Aneurysm
|
0/8(0.0%)
|
0/45 (0.0%)
|
0/17 (0.0%)
|
-
|
|
|
Sphenoid wing dysplasia
|
0/8 (0.0%)
|
3/45 (6.7%)
|
2/17 (11.8%)
|
0.791
|
|
|
Superficial neurofibromas
|
0/8 (0.0%)
|
2/45 (4.4%)
|
0/17 (0.0%)
|
1.000
|
|
|
Deep localized neurofibromas
|
0/8 (0.0%)
|
2/45 (4.4%)
|
2/17 (11.8%)
|
0.574
|
|
|
Plexiform neurofibromas
|
1/8 (12.5%)
|
3/45 (6.7%)
|
4/17 (23.5%)
|
0.171
|
|
|
Scoliosis
|
0/8 (0.0%)
|
0/45 (0.0%)
|
1/17 (5.9%)
|
0.357
|
|
|
Spinal dysplasia
|
0/8 (0.0%)
|
0/45 (0.0%)
|
0/17 (0.0%)
|
-
|
|
|
Spinal dural ectasia
|
0/8 (0.0%)
|
6/45 (13.3%)
|
3/17 (24.3%)
|
0.572
|
|
|
Long bond dysplasia
|
0/8 (0.0%)
|
4/45 (8.9%)
|
2/17 (11.8%)
|
0.842
|
|
|
MPNST
|
0/8 (0.0%)
|
0/45 (0.0%)
|
0/17 (0.0%)
|
-
|
|
NF1+
|
|
2/8 (25.0%)
|
13/45 (28.9%)
|
12/17 (70.6%)
|
0.008
|
|
FASI focal areas of signal intensity, MPNST malignant peripheral nerve sheath tumor |
The most frequent NF1-related typical manifestation was CALMs (70/70, 100%), followed by relative macrocephaly (37/67, 55.2%), axillary freckling (28/62, 45.2%), Lisch nodules (8/25, 32.0%), and cutaneous neurofibromas (7/40, 17.5%). Neurologic problems, such as developmental delay or seizure, were reported in 9.5% (4/42) and 5.3% (2/38) of patients, respectively. Short stature was reported in 2.9% (2/70) of patients. Atrial septal defect was reported in one patient, which was spontaneously closed during follow-up. Developmental delay (30.0% vs 3.1%, p = 0.036), PN (28.6% vs 5.7%, p = 0.030), and NF1+ (71.4% vs 30.2%, p = 0.011) was more commonly observed in familial cases (Fig. 2A).
The most frequent WBMRI finding at the first evaluation was focal areas of signal intensity (FASI; 47/70, 67.1%), followed by optic pathway glioma (11/70, 15.7%), bony dysplasia (10/70, 14.3%), suspicious mild spinal dura ectasia (9/70, 12.9%), and PN (8/70, 11.4%). Regarding FASI, the cerebellum (72.3%) was the most frequently involved site, followed by basal ganglia (38.3%), brainstem (31.9%), internal capsule (23.4%), and thalamus (10.6%). Less frequently, FASI was also found in the left parietal cortex (1/47, 2.1%), dentate (1/47, 2.1%), midbrain (1/47, 2.1%), centrum semiovale (1/47, 2.1%), and anterior commissure (1/47, 2.1%). The involved bony dysplasia sites were sphenoid wing (5/10, 50.0%), tibia and/or fibula (4/10, 40.0%), pubis and ischium (1/10, 10.0%), and sacrum (1/10, 10.0%). Representative cases are shown in Fig. 3.
Importantly, a few cases with extraordinary manifestations were noted. A 1.5-year-old girl (NF1 c.4110 + 2T > G (IVS30(+2)T > G)) had a germ cell tumor in the pelvic area with bone, lung, and lymph node metastasis (Fig. 4A, B). A 1.8-year-old boy (NF1 c.1307C > A (p.S436*)) with infantile spasm, hypsarrythmia, and developmental arrest was diagnosed with West syndrome and had moyamoya disease and a horseshoe kidney in WBMRI (Fig. 4C).
The remaining 11 patients (15.7%, four girls and seven boys; mean age, 1.4 ± 0.4 years) had no radiologic abnormalities related to NF1 on WBMRI. No significant differences in gender (22 males and 37 females with WBMRI abnormality vs seven males and four females without WBMRI abnormality, p = 0.181) or age (1.6 ± 0.7 years vs 1.4 ± 0.4 years, p = 0.07) were noted between the patients with and without abnormalities in WBMRI.
When the frequency of the clinical phenotypes was analyzed according to age at WBMRI evaluation, the frequency of most phenotypes increased in patients 2–3 years old. Moreover, the frequency of axillary freckling, optic pathway glioma, and NF1+ significantly increased (P < 0.05; Table 1).
NF1 diagnosis
Fifty-two (74.3%) patients fulfilled the previous NIH diagnostic criteria. Among 18 patients who had CALMs in NIH diagnostic criteria and confirmed NF1 by genetic testing, 50% (4/8) of the patients were younger than 1 year old, and 31.1% (14/45) of the patients were 1–2 years old. In patients who did not meet the previous NIH criteria, relative macrocephaly, FASI, sphenoid dura ectasia, spinal dura ectasia, and seizure were observed in nine (50.0%), eight (44.4%), six (33.3%), three (33.3%), and one (5.6%) patient, respectively.
In contrast, all patients met the revised diagnostic criteria for NF1; 66 patients with at least CALMs and heterozygous pathogenic NF1 variants; 3 patients with CALMs and axillary freckling; 1 patient with CALMs and a positive family history.
Molecular findings and genotype–phenotype correlation
Long-range PCR and sequencing of gDNA and MLPA analyses identified NF1 mutations in 87.1% and 7.1% of patients, respectively. The mutation type distributions were frameshift mutations (N = 21, 31.8%), nonsense mutations (N = 16, 24.2%), missense mutations (N = 13, 19.7%), splice-site mutations (N = 11, 16.7%), and large deletions (N = 5, 7.6%; Fig. 1). Deep localized neurofibroma was more prevalent in missense mutations than other mutation types (Fig. 2B).
The NF1 functional domains affected by each NF1 mutation were assessed. Syn domain was most commonly affected (52/66, 78.8%), followed by pleckstrin homology (PH; 46/66, 69.7%), GRD (45/66, 68.2%), Sec14 homology-like domain (SEC14; 44/66, 67.5%), tubulin binding (35/66, 53.0%), and CSRD (26/66, 39.4%) domains. The frequency of phenotypes were assessed according to the affected domains, and FASI was more prevalent (77.8% vs 52.4%, p = 0.047; Fig. 2C, Supplemental Table 2) in patients with NF1 mutation affecting GRD involvement.
Progression during follow-up
Follow-up MRI was performed in 42 (60.0%) patients (23 girls and 19 boys; mean age, 2.78 ± 0.91 years). The mean duration between the baseline and follow-up MRIs was 1.21 ± 0.50 years. In addition, 19 (45.2%) patients exhibited progression during follow-up: clinical, radiological, and both clinical and radiological progressions were shown in six, nine, and four patients, respectively. The detailed clinical and radiological findings of the patients who showed progression during follow-up are summarized in Supplementary Table 3 and a representative case was shown in Supplementary figure 1. The common phenotypes exhibiting progression were developmental delay in language (N = 7) or fine motor (N = 3) according to KICDT. The patient with West syndrome did not achieve any developmental milestones during follow-up. In the follow-up WBMRI, the radiologic aspects, optic nerve signal change or thickening, were newly developed in eight patients. Additionally, optic nerve signal change and severe PN (one patient), severe PN and diffuse superficial neurofibroma (one patient), nerve root tumor (one patient), brain tumor on pons (one patient), and neuroblastoma in the left adrenal gland (one patient) were also newly developed.
Clinical and genotypic features were compared between patients experiencing or not experiencing disease progression. Gender, inheritance mode, and mutations type were not associated with disease progression. However, disease progression was observed in higher proportion in patients with NF1 mutation affecting GRD (61.5% vs 15.8%, p = 0.041), SEC (64.0% vs 21.4%, p = 0.019), and PH (64.0% vs 21.4%, p = 0.019) domains. Radiological progression was especially more frequently observed in patients with NF1 mutations affecting the GRD domain (46.2% vs. 7.7%, p = 0.029; Fig. 2D), whereas no significant differences were observed among those with NF1 mutations affecting other domains. No significant differences were noted in the prevalence of clinical progression among the affected domains of NF1 mutations.