The second family affected with a PRDM8-related disease.

INTRODUCTION: Lafora disease (LD) is a severe form of progressive myoclonus epilepsy characterized by generalized seizures, myoclonus, intellectual decline, ataxia, spasticity, dysarthria, visual loss, and in later stages, psychosis and dementia. To date, mutations in the EPM2A and EPM2B/NHLRC1 genes have been identified as the common causes of LD. However, a mutation in PRDM8 has been reported only once in a Pakistani family affected with early-onset Lafora disease. In the present study, we report the second family with a PRDM8 mutation. METHODS: Two affected individuals of an Iranian family initially diagnosed as complicated hereditary spastic paraplegia (HSP) underwent careful neurologic examination. Homozygosity mapping and whole-exome sequencing were performed. Based on the results of genetic analysis to detection of Lafora bodies, a skin biopsy was done. RESULTS: The clinical features of the patients were described. Linkage to chromosome 4 and a mutation in the PRDM8 gene were identified, suggesting the patients may be affected with early-onset LD. However, like the Pakistani family, the search for Lafora bodies in their skin biopsies was negative. Their electroencephalograms showed generalized epileptiform discharges in the absence of clinical seizures. CONCLUSIONS: The current study increases the number of PRDM8-related cases and expands the phenotypic spectrum of mutations in the PRDM8 gene. Both reported PRDM8-related families presented intra and inter-familial heterogeneity and they have originated from the Middle East. Thus, it seems the PRDM8 mutations should be considered not only in LD but also in other neurodegenerative disorders such as a complicated HSP-like phenotype, especially in this region.

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.

Description of combined ARHSP/JALS phenotype in some patients with SPG11 mutations.

BACKGROUND: SPG11 mutations can cause autosomal recessive hereditary spastic paraplegia (ARHSP) and juvenile amyotrophic lateral sclerosis (JALS). Because these diseases share some clinical presentations and both can be caused by SPG11 mutations, it was considered that definitive diagnosis may not be straight forward. METHODS: The DNAs of referred ARHSP and JALS patients were exome sequenced. Clinical data of patients with SPG11 mutations were gathered by interviews and neurological examinations including electrodiagnosis (EDX) and magnetic resonance imaging (MRI). RESULTS: Eight probands with SPG11 mutations were identified. Two mutations are novel. Among seven Iranian probands, six carried the p.Glu1026Argfs*4-causing mutation. All eight patients had features known to be present in both ARHSP and JALS. Additionally and surprisingly, presence of both thin corpus callosum (TCC) on MRI and motor neuronopathy were also observed in seven patients. These presentations are, respectively, key suggestive features of ARHSP and JALS. CONCLUSION: We suggest that rather than ARHSP or JALS, combined ARHSP/JALS is the appropriate description of seven patients studied. Criteria for ARHSP, JALS, and combined ARHSP/JALS designations among patients with SPG11 mutations are suggested. The importance of performing both EDX and MRI is emphasized. Initial screening for p.Glu1026Argfs*4 may facilitate SPG11 screenings in Iranian patients.