Exon 8-17 deletions of SPAST in a Chinese family with hereditary spastic paraplegia: a case report and literature review

Clinical and Genetic Spectrum in a Large Cohort of Hereditary Spastic Paraplegia

BACKGROUND

Next-generation sequencing-based molecular assessment has benefited the diagnosis of hereditary spastic paraplegia (HSP) subtypes. However, the clinical and genetic spectrum of HSP due to large fragment deletions/duplications has yet to be fully defined.

OBJECTIVE

We aim to better characterize the clinical phenotypes and genetic features of HSP and to provide new thoughts on diagnosis.

METHODS

Whole-exome sequencing (WES) was performed in patients with clinically suspected HSP, followed by multiple ligation-dependent probe amplification (MLPA) sequentially carried out for those with negative findings in known causative genes. Genotype-phenotype correlation analyses were conducted under specific genotypes.

RESULTS

We made a genetic diagnosis in 60% (162/270) of patients, of whom 48.9% (132/270) had 24 various subtypes due to point mutations (SPG4/SPG11/SPG35/SPG7/SPG10/SPG5/SPG3A/SPG2/SPG76/SPG30/SPG6/SPG9A/SPG12/SPG15/SPG17/SPG18/SPG26/SPG49/SPG55/SPG56/SPG57/SPG62/SPG78/SPG80). Thirty patients were found to have causative rearrangements by MLPA (11.1%), among which SPG4 was the most prevalent (73.3%), followed by SPG3A (16.7%), SPG6 (3.3%), SPG7 (3.3%), and SPG11 (3.3%). Clinical analysis showed that some symptoms were often related to specific subtypes, and rearrangement-related SPG3A patients seemingly had later onset. We observed a presumptive anticipation among SPG4 and SPG3A families due to rearrangement.

CONCLUSIONS

Based on the largest known Asian HSP cohort, including the largest subgroup of rearrangement-related pedigrees, we gain a comprehensive understanding of the clinical and genetic spectrum of HSP. We propose a diagnostic flowchart to sequentially detect the causative genes in practice. Large fragment mutations account for a considerable proportion of HSP, and thus, MLPA screening acts as a beneficial supplement to routine WES. © 2024 International Parkinson and Movement Disorder Society.

Copy Number Variations in Hereditary Spastic Paraplegia-Related Genes: Evaluation of an Iranian Hereditary Spastic Paraplegia Cohort and Literature Review

Introduction

In human genetic disorders, copy number variations (CNVs) are considered a considerable underlying cause. CNVs are generally detected by array-based methods but can also be discovered by read-depth analysis of whole-exome sequencing (WES) data. We performed WES-based CNV identification in a cohort of 35 Iranian families with hereditary spastic paraplegia (HSP) patients.

Methods

Thirty-five patients whose routine single-nucleotide variants (SNVs) and insertion/deletion analyses from exome data were unrevealing underwent a pipeline of CNV analysis using the read-depth detection method. Subsequently, a comprehensive search about the existence of CNVs in all 84 known HSP-causing genes was carried out in all reported HSP cases, so far.

Results and Discussion

CNV analysis of exome data indicated that 1 patient harbored a heterozygous deletion in exon 17 of the SPAST gene. Multiplex ligation-dependent probe amplification analysis confirmed this deletion in the proband and his affected father. Literature review demonstrated that, to date, pathogenic CNVs have been identified in 30 out of 84 HSP-causing genes (∼36%). However, CNVs in only 17 of these genes were specifically associated with the HSP phenotype. Among them, CNVs were more common in L1CAM, PLP1, SPAST, SPG7, SPG11, and REEP1 genes. The identification of the CNV in 1 of our patients suggests that WES allows the detection of both SNVs and CNVs from a single method without additional costs and execution time. However, because of intrinsic issues of WES in the detection of large rearrangements, it may not yet be exploited to replace the CNV detection methods in standard clinical practice.

Anticipation Can Be More Common in Hereditary Spastic Paraplegia with SPAST Mutations Than It Appears

BACKGROUND AND OBJECTIVE

Hereditary spastic paraplegia (HSP) is a heterogeneous neurodegenerative disorder with lower-limb spasticity and weakness. Different patterns of inheritance have been identified in HSP. Most autosomal-dominant HSPs (AD-HSPs) are associated with mutations of the SPAST gene (SPG4), leading to a pure form of HSP with variable age-at-onset (AAO). Anticipation, an earlier onset of disease, as well as aggravation of symptoms in successive generations, may be correlated to SPG4. Herein, we suggested that anticipation might be a relatively common finding in SPG4 families.

METHODS

Whole-exome sequencing was done on DNA of 14 unrelated Iranian AD-HSP probands. Data were analyzed, and candidate variants were PCR-amplified and sequenced by the Sanger method, subsequently checked in family members to co-segregation analysis. Multiplex ligation-dependent probe amplification (MLPA) was done for seven probands. Clinical features of the probands were recorded, and the probable anticipation was checked in these families. Other previous reported SPG4 families were investigated to anticipation.

RESULTS

Our findings showed that SPG4 was the common subtype of HSP; three families carried variants in the KIF5A, ATL1, and MFN2 genes, while five families harbored mutations in the SPAST gene. Clinical features of only SPG4 families indicated decreasing AAO in affected individuals of the successive generations, and this difference was significant (p-value <0.05).

CONCLUSION

It seems SPAST will be the first candidate gene in families that manifests a pure form of AD-HSP and anticipation. Therefore, it may be a powerful situation of genotype-phenotype correlation. However, the underlying mechanism of anticipation in these families is not clear yet.

Trigeminal Ganglion Metastasis of Renal Clear Cell Carcinoma: Cases Report and Review of the Literature

BACKGROUND

The trigeminal ganglion is an atypical site for metastasis, especially for renal clear cell carcinoma.

CASE DESCRIPTION

We report 2 clinical cases of a 66-year-old man and a 58-year-old man with trigeminal symptoms. Both patients had a history of renal clear cell (RCC) that was considered to be cured at 6 and 9 years, respectively. Brain magnetic resonance imaging (MRI) showed a trigeminal ganglion lesion with increased gadolinium enhancement associated with petrous apex erosion. The main diagnostic hypothesis based on MRI was trigeminal schwannoma for both patients. One patient underwent subtotal removal, the other a biopsy. Histologic examinations resulted in the diagnosis of RCC metastasis. Body computed tomography revealed pancreatic metastasis for both but no renal recurrence. The patients were treated by local radiotherapy, and 1 of the patients had associated chemotherapy. We added to these clinical cases a literature review of skull base metastasis of RCC. Trigeminal ganglion metastasis of RCC is very rare and can persist until 10 years after the first RCC diagnosis. It seems that the best treatment is surgical removal. To date, the role of local radiotherapy is not demonstrated, and the prognosis seems to be poor.

CONCLUSIONS

In the case of trigeminal symptoms, rapid tumoral growth on brain MRI, or a history of RCC, we think that a body computed tomography should be performed, and surgery should be considered.

Renal Cell Carcinoma with Primary Presentation via Metastasis to the Trigeminal Ganglion

BACKGROUND

Renal cell carcinoma (RCC) accounts for ∼8% of all brain metastatic disease; however, spread to the cranial nerves and their ganglia is uncommon. To the best of our knowledge, we report the first case of RCC metastatic to Meckel's cave, which was diagnosed secondary to new trigeminal sensory loss.

METHODS

A 45-year-old man had presented with acute-onset right V3 numbness. Magnetic resonance imaging demonstrated contrast enhancement of the ipsilateral V3, extending from its root at the Gasserian ganglion to the foramen ovale.

RESULTS

He elected for observation, and his symptoms resolved over several weeks. At the scheduled, routine 3-month follow-up examination, he reported symptomatic relapse with new concomitant hyperesthetic/neuropathic pain. Magnetic resonance imaging demonstrated interval enlargement of the enhancing lesion in an atypical pattern, potentially consistent with trigeminal schwannoma versus meningioma, and operative resection was recommended.

CONCLUSION

We have reported a case of RCC presenting with numbness via metastatic spread to Meckel's cave. Although uncommon, metastasis is an important diagnostic consideration for enhancing cranial nerve lesions. Our case has demonstrated that, although a history of malignancy, multiple lesions, or systemic/constitutional symptoms are typical, rare cases can demonstrate isolated central nervous system findings. Thus, short-term radiographic surveillance is indicated if the diagnosis of an intracranial or cranial nerve mass lesion is equivocal.