Genotype-phenotype correlations of neurofibromatosis type 1: a cross-sectional study from a large Chinese cohort

BACKGROUND

Neurofibromatosis type 1 (NF1) is a highly heterogeneous autosomal genetic disorder characterized by a broad spectrum of clinical and molecular manifestations. The correlations between genotype and phenotype in NF1 remain elusive. This study aimed to elucidate genotype-phenotype associations in a large Chinese cohort of NF1 patients.

METHODS

We included NF1 patients from our center who underwent genetic testing for NF1 variants and systemic examination. Genotype-phenotype correlation analyses were performed, focusing on variation types and involved neurofibromin domains.

RESULTS

A total of 195 patients were enrolled, comprising 105 males and 90 females, with a median age of 18 years. Truncating variants, single amino acid variations, and splicing variants accounted for 139/195 (71.3%), 23/195 (11.8%), and 33/195 (16.9%), respectively. Patients with splicing variants exhibited a significantly higher prevalence of spinal plexiform neurofibromas (spinal PNF) than those with truncating variants (76.4% vs. 51.8%; p = 0.022). Variations affecting the PKC domain were associated with higher rates of cutaneous neurofibromas (CNF) (100% vs. 64.9%, p < 0.001), Lisch nodules (100% vs. 61.2%, p < 0.001), plexiform neurofibromas (PNF) (100% vs. 95.7%, p = 0.009), and psychiatric disorders (11.8% vs. 1.6%, p = 0.042). Patients with mutations in the CSRD had an elevated risk of secondary primary malignancies (11.6% vs. 2.8%, p = 0.015). GRD involvement might enhance the risk of Lisch nodules (76.9% vs. 53.7%, p = 0.044). Variations in the Sec14-PH domain were correlated with a higher rate of CNF (76.8% vs. 58.6%, p = 0.014). Additionally, we found that the p.R1748* variants carry a high risk of malignancy.

CONCLUSION

Our study suggested some novel genotype-phenotype correlations within a Chinese cohort, providing innovative insights into this complex field that may contribute to genetic counseling, risk stratification, and clinical management for the NF1 population.

Quality of Life in Children and Adolescents with Neurofibromatosis Type 1: A Single-Center Observational Study

This article obtains an overview of the health status of children and adolescents with neurofibromatosis type 1 (NF1) with a focus on the clinical course of the disease, neuropsychodiagnostic findings, and their impact on quality of life (QoL). In this observational study, data were collected from 24 children and adolescents with NF1 who were cared for at the University Hospital in Innsbruck, Austria, from 2008 to 2022. Data were collected every 6 to 12 months from routine check-ups, including clinical features and imaging findings. Results of neuropsychodiagnostic tests and the KINDL questionnaire to assess QoL were included. Of 24 patients, 15 underwent a neuropsychological examination. Attention performance was examined in 11 of them. Eight of 11 (72%) showed an attention deficit. Assessment for specific developmental disorders showed visual-spatial difficulties in 12/15 (80%) patients. The KINDL questionnaire values ranged from 58.22 to 97.92 (0 stands for reduced QoL, 100 for very good QoL). Patients with scoliosis had a lower range of QoL (56.33-73.96). No trend in QoL was observed in children and adolescents with plexiform neurofibromas, below-average intelligence or optic gliomas. NF1 patients show very different clinical courses. Regular neuropsychological assessment especially with regard to visual-spatial skills and attention deficits is necessary to offer appropriate support, promote children's development, and thus improve their QoL.

Evaluation of Molecular and Clinical Findings in Children With Neurofibromatosis Type 1: Identification of 15 Novel Variants

BACKGROUND

Neurofibromatosis type 1 (NF1) is the most common neurocutaneous disease and is caused by mutations in the NF1 gene. The most common clinical features of NF1 are pigmentary abnormalities such as café-au-lait spots and inguinal or axillary freckling, cutaneous and plexiform neurofibromas, hamartomas of the iris, optic gliomas, and bone lesions. The aim of this retrospective study was to define the clinical and molecular characteristics of a pediatric sample of NF1, as well as the mutational spectrum and genotype-phenotype correlation.

METHODS

The study included 40 children with clinically suspected NF1. The patients were screened for NF1 mutations by DNA-based sequencing. In addition, all the patients were studied by multiplex ligation-dependent probe amplification (MLPA) to identify any duplications or deletions in NF1. The demographic, clinical, and genetic features of the children were characterized.

RESULTS

A total of 40 children with NF1 were included. Of those, 28 were female and 12 were male. The mean age was 8.91 years. An NF1 variant was discovered in 28 of 40 patients (70%). Among these mutations, intronic mutations were the most frequently detected mutations; 15 of these variants had not been previously reported. Only one patient had a whole NF1 gene deletion.

CONCLUSIONS

This study expands the spectrum of mutations in the NF1 gene. This study also showed that genetic screening using both next-generation sequencing and MLPA had a positive effect on diagnosis and genetic counseling in patients with suspected NF1.

Retrospective Cohort Analysis of the Impact of Puberty on Plexiform Neurofibroma Growth in Patients with Neurofibromatosis Type 1

OBJECTIVE

To assess the hypothesis that plexiform neurofibroma (PN) growth rates increase during puberty.

STUDY DESIGN

PN growth rates before and during puberty were compared in a retrospective cohort of children with neurofibromatosis type 1 with puberty defined by Tanner staging. Of 33 potentially eligible patients, 25 had adequate quality magnetic resonance imaging for volumetric analysis and were included in ≥1 anchor cohort. Volumetric analysis was performed for all available imaging studies within the 4 years before and after puberty, and before and after 9- and 11-year-old anchor scans. Linear regression was performed to estimate the slope of change (PN growth rate); growth rates were compared with paired t test or Wilcoxon matched-pairs signed rank test.

RESULTS

There were no significant difference in rates of PN growth in milliliters per month or milliliters per kilogram per month in the prepubertal vs pubertal periods (mean, 1.33 ± 1.67 vs 1.15 ± 1.38 [P = .139] and -0.003 ± 0.015 vs -0.002 ± 0.02 [P = .568]). Percent increases of PN volumes from baseline per month were significantly higher prepubertally (1.8% vs 0.84%; P = .041) and seemed to be related inversely to advancing age.

CONCLUSIONS

Puberty and its associated hormonal changes do not seem to influence PN growth rate. These findings support those previously reported, but from a typical population of children with neurofibromatosis type 1 with puberty confirmed by Tanner staging.

Runx1/3-driven adaptive endoplasmic reticulum stress pathways contribute to neurofibromagenesis

Neurofibromatosis type 1 (NF1) patients are predisposed to develop plexiform neurofibromas (PNFs). Three endoplasmic reticulum (ER) stress response pathways restore cellular homeostasis. The unfolded protein response (UPR) sensors contribute to tumor initiation in many cancers. We found that all three UPR pathways were activated in mouse and human PNFs, with protein kinase RNA [PKR]-like ER kinase (PERK) the most highly expressed. We tested if neurofibroma cells adapt to ER stress, leading to their growth. Pharmacological or genetic inhibition of PERK reduced mouse neurofibroma-sphere number, and genetic inhibition in PERK in Schwann cell precursors (SCPs) decreased tumor-like lesion numbers in a cell transplantation model. Further, in a PNF mouse model, deletion of PERK in Schwann cells (SCs) and SCPs reduced tumor size, number, and increased survival. Mechanistically, loss of Nf1 activated PERK-eIF2α-ATF4 signaling and increased ATF4 downstream target gene p21 translocation from nucleus to cytoplasm. This nucleus-cytoplasm translocation was mediated by exportin-1. Runx transcriptionally activated ribosome gene expression and increased protein synthesis to allow SCs to adapt to ER stress and tumor formation. We propose that targeting proteostasis might provide cytotoxic and/or potentially durable novel therapy for PNFs.

Plexiform Neurofibroma Without Neurofibromatosis Type 1

Dear Editor, Plexiform neurofibroma (PNF) is a particular subtype of benign nerve sheath tumors with a reticular growth pattern not respecting tissue borders and involving several nerve branches or fascicles. It is most commonly reported in patients with neurofibromatosis type-1 (NF-1) and represents in up to 30% of NF-1 patients (1,2). Other possible associations include schwannomatosis, multiple cutaneous schwannomas syndrome, and rarely neurofibromatosis type-2 (NF-2) (3). PNF develops as a result of tumor proliferation to all parts of the peripheral nervous system. It may cause functional and cosmetic impairment, pain, and a certain risk of malignant transformation in internal organs in some critical cases (4,5). Malignant peripheral nerve sheath tumors occur in about 10% of NF-1 patients (4,5). NF-1 is caused by mutations in the NF-1 tumor-suppressor gene, which encodes a GTPase-Activating Protein (GAP) that negatively regulates p21-RasNF1 (6). These patients have a predisposition to develop both benign and malignant tumors (6). Isolated or NF-1-associated cutaneous or superficial PNF, however, do not transform into their malignant counterpart (1). We report an isolated case of a plexiform PNF in a 16-year-old girl without NF-1. A-16-year-old Caucasian woman presented with a slow-growing exophytic nodule on her right flank. The tumor was asymptomatic, and tumor removal was requested for esthetic reasons. The patient was otherwise healthy. Her family history was negative for hereditary disorders. She was taking no medications at the time. On examination, a 1.8×1.6 cm large, slow-growing, and asymptomatic exophytic asymptomatic tumor was observed on the right flank (Figure 1). The primary suspicion was a complex nevus tumor type such as nevus sebaceous or nevus lipomatosus. The tumor was surgically removed, and the defect was closed by tissue expansion. Histology revealed a spindle-cell proliferation of S-100 positive cells without cellular atypia and myxoid stroma (Figure 2). The diagnosis of PNF was thus established. Healing was uneventful. There were no clinical signs of NF-1 or NF-2. We reported a case of PNF without NF-1 or NF-2. The diagnosis of an isolated PNF is a very rare event (7-10). In a large study from Lima lasting 33 years, only one isolated PNF not associated with NF-1 was observed. In this patient, PNF developed in the oral mucosa (7). An isolated PNF causing an auricular deformity has been previously observed in a 14-year-old boy (8). In India, a 11-year-old girl with an isolated PNF of the tongue was reported (9). Isolated PNFs are not necessarily limited to children and adolescents but may also occur later in life (10). The gold standard of treatment is surgical intervention. In case of unresectable and painful tumors, interferon alfa is a medical option (11). Other drugs are under evaluation, such as oral selumetinib, a selective inhibitor of MAPK kinase 1 and 2, AZD8055, an ATP-competitive "active-site" mTOR inhibitor, or a BromoDomain-containing protein 4-inhibitor (12,13). In conclusion, isolated PNF is a very rare observation. In case of impairment, surgery - whenever possible - is the preferred treatment option (8).

[A Case of Neurofibromatosis Type 1 Presenting Voiding Symptoms Caused by Giant Bladder Diverticulum]

A 40-year-old man complaining of voiding symptoms was referred to our hospital for further examinations and treatment of giant bladder diverticulum and possibly underlying neurogenic bladder dysfunction. Because computed tomography and magnetic resonance imaging revealed the presence of a tumorous lesion covering the bladder diverticulum, transurethral biopsy was performed to elucidate its pathological characteristics. Through the histopathological examination of the biopsy specimens the tumorous lesion was diagnosed as ganglioneuroma which was benign. The whole diverticulum with the concomitant tumor lesion was surgically excised. Full examination of the surgical specimen concluded the final histopathological diagnosis of the tumor to be plexiform neurofibroma. As multiple café-au-lait spots were found on the patient's skin, he was clinically diagnosed with neurofibromatosis type 1.

Diagnostic sequence for early diagnosis of neurofibromatosis type 1 using NIH criteria

Early diagnosis of neurofibromatosis is significant to start the multidisciplinary approach of this type of patient. This syndrome may be first identified in pediatric dental care. This study is about a 9-year-old patient who was diagnosed with neurofibromatosis type 1 from a plexiform neurofibroma displayed in the left hemi-maxilla. From the microscopic diagnosis of the lesion the investigation of other related injuries began, according to the diagnostic criteria of the National Institute of Health (NIH), leading to the diagnosis of systemic alterations. The parental awareness about the condition and the establishment of multidisciplinary care are important for the treatment to be more conservative and the patient has fewer complications with better quality of life. The use of the diagnostic criteria in this case shows how methodization is important for reaching more accurate and reliable diagnoses.

Endovascular management of renal artery aneurysms induced by neurofibromatosis type 1: A case report

RATIONALE

Neurofibromatosis type 1 (NF-1) is an autosomal dominant disorder characterized by cafe au lait macules and neurofibromatosis. Renal artery aneurysms are relatively uncommon. Endovascular techniques are effective in treating renal aneurysms but successful cases are rarely reported in NF-1 adults.

PATIENT CONCERNS

The patient was one 23-year-old female presented with hypertension, multiple café-au-lait spots ≥15 mm, and plexiform neurofibroma. Renal artery aneurysms were found by ultrasound.

DIAGNOSES

NF-1 was diagnosed based on clinical manifestations and confirmed by gene test. Renal artery aneurysms were diagnosed based on computed tomography.

INTERVENTIONS

Bilateral renal artery angiography was performed and 3 aneurysms were found sequentially on the left anterior superior segmental artery. Microcoil embolization of aneurysms was undertaken.

OUTCOMES

The patient's blood pressure decreased after the procedure with reduction of medicine. A 3-month follow-up unilateral selective renal angiogram demonstrated little change in size of aneurysms, and no opacification of the aneurysmal sac was found. Serum creatinine remained in normal range at 3-month.

LESSONS

Successful endovascular treatment for NF-1 related renal artery aneurysms in adults is reported for the 1st time with preserved renal function and improved hypertension. Endovascular procedure is considered to be feasible and effective for renal artery aneurysms induced by NF-1.

Su Un Raro Caso di Neurofibroma Plessiforme Del Pavimento Orale

A case of plexiform neurofibroma of the oral floor is described, its rarity underlined and its pathogenesis discussed. The different hypotheses concerning the tumours of the peripheral nervous system are referred and cases from the literature showing similarities with the one under examination are reviewed.

Medullated corneal nerves and plexiform neuroma associated with pheochromocytoma

Images