Clinical profiling of MRD48 and functional characterization of two novel pathogenic RAC1 variants

RAC1 is a member of the Rac/Rho GTPase subfamily within the RAS superfamily of small GTP-binding proteins, comprising 3 paralogs playing a critical role in actin cytoskeleton remodeling, cell migration, proliferation and differentiation. De novo missense variants in RAC1 are associated with a rare neurodevelopmental disorder (MRD48) characterized by DD/ID and brain abnormalities coupled with a wide range of additional features. Structural and functional studies have documented either a dominant negative or constitutively active behavior for a subset of mutations. Here, we describe two individuals with previously unreported de novo missense RAC1 variants. We functionally demonstrate their pathogenicity proving a gain-of-function (GoF) effect for both. By reviewing the clinical features of these two individuals and the previously published MRD48 subjects, we further delineate the clinical profile of the disorder, confirming its phenotypic variability. Moreover, we compare the main features of MRD48 with the neurodevelopmental disease caused by GoF variants in the paralog RAC3, highlighting similarities and differences. Finally, we review all previously reported variants in RAC proteins and in the closely related CDC42, providing an updated overview of the spectrum and hotspots of pathogenic variants affecting these functionally related GTPases.

The relevance of MRI blood-sensitive sequences in the diagnostic assessment of late-onset epilepsy

OBJECTIVE

Sporadic cerebral amyloid angiopathy (CAA) is a degenerative brain small vessel disease of ageing resulting from progressive amyloid deposition in small arteries and arterioles of the cortex and leptomeninges. CAA may be diagnosed by the mean of Boston criteria, particularly with the use of the blood-sensitive T2* MRI sequences (GRE and SWI). Epileptic seizures have rarely been reported in CAA.

PATIENTS AND METHODS

We describe two patients with late-onset unprovoked seizures due to CAA. A short literature review on this topic is presented.

RESULTS

In our two patients with late-onset unprovoked seizures as the first manifestation of CAA, only GRE and SWI sequences lead to a correct diagnosis. In literature, only 15 patients with CAA presenting with seizures have been reported. In these subjects, data on seizures semiology and prognosis are scarce.

CONCLUSIONS

Our report highlights the importance to perform blood-sensitive sequences in all subjects with LOE of otherwise unknown etiology, not to miss a diagnosis of CAA.

Novel COL4A2 mutation causing familial malformations of cortical development

OBJECTIVE

This article aimed to describe a novel COL4A2 mutation and the phenotypic features of two family members presenting with epilepsy and cortical development malformations.

PATIENTS AND METHODS

The first patient is a 65-year-old woman with hematuria and adult-onset seizures. Brain MRI showed closed lip schizencephaly of right lateral sulcus associated with polymicrogyria of the surrounding cortex and areas of subcortical heterotopia. The second patient is a 40-year-old man, her son. He was born post-term with neonatal distress and psychomotor developmental delay with congenital left leg paresis and strabismus, as well as childhood-onset focal motor seizures. Brain MRI showed a right nucleus-capsular porencephalic cavitation with enlargement of the homolateral ventricle and a focal right occipital cortico-subcortical encephalomalacia. A small heterotopic band was also present in the frontal left subcortical region.

RESULTS

We tested both patients with a NGS panel for genetic epilepsies, which evidenced a missense mutation in COL4A2 gene (c.2972G>A, causing the aminoacidic substitution Gly991Glu).

CONCLUSIONS

The phenotypic spectrum associated with COL4A2 mutations has not been extensively described in the literature. Testing for COL4A mutations is indicated in patients with malformations of cortical development, particularly in the presence of familial conditions, even in the absence of porencephaly or early hemorrhagic strokes.

Co-Occurring Heterozygous CNOT3 and SMAD6 Truncating Variants: Unusual Presentation and Refinement of the IDDSADF Phenotype

Objective, the application of genomic sequencing in clinical practice has allowed us to appreciate the contribution of co-occurring pathogenic variants to complex and unclassified clinical phenotypes. Besides the clinical relevance, these findings have provided evidence of previously unrecognized functional links between genes in the context of developmental processes and physiology. Patients and Methods, a 5-year-old patient showing an unclassified phenotype characterized by developmental delay, speech delay, peculiar behavioral features, facial dysmorphism and severe cardiopathy was analyzed by trio-based whole exome sequencing (WES) analysis to identify the genomic events underlying the condition. Results, two co-occurring heterozygous truncating variants in CNOT3 and SMAD6 were identified. Heterozygous loss-of-function variants in CNOT3, encoding a subunit of the CCR4-NOT protein complex, have recently been reported to cause a syndromic condition known as intellectual developmental disorder with speech delay, autism and dysmorphic facies (IDDSADF). Enrichment of rare/private variants in the SMAD6 gene, encoding a protein negatively controlling transforming growth factor β/bone morphogenetic protein (TGFB/BMP) signaling, has been described in association with a wide spectrum of congenital heart defects. We dissected the contribution of individual variants to the complex clinical manifestations and profiled a previously unappreciated set of facial features and signs characterizing IDDSADF. Conclusions, two concomitant truncating variants in CNOT3 and SMAD6 are the cause of the combination of features documented in the patient resulting in the unique multisystem neurodevelopmental condition. These findings provide evidence for a functional link between the CCR4-NOT complex and TGFB/BMP signaling in processes controlling cardiac development. Finally, the present revision provides evidence that IDDSADF is characterized by a distinctive facial gestalt.

Epileptogenic role of occult temporal encephalomeningocele

Objective

The purpose of this case-control study is to evaluate the prevalence of occult temporal encephalomeningocele (OTE) in patients with temporal lobe epilepsy (TLE) of unknown etiology presenting to an epilepsy center, independently from drug sensitivity.

Methods

We studied 95 patients with TLE (51 female, mean age 49.4 ± 17.1 years) and 151 controls (88 female, mean age 54.1 ± 21.0 years) using a 1.5T brain MRI, including balanced steady-state gradient echo sequences, targeted to the temporal lobes.

Results

OTE was found in 5.2% of the TLE population (9.5% of drug-resistant TLE) and in none of the controls (p = 0.008). Two patients with OTE and drug-resistant TLE became seizure-free after lesionectomy (follow-up 18–24 months).

Conclusion

OTE is not a rare finding in unselected patients with TLE of unknown origin, provided that it is carefully searched. The absence of OTE in a large group of nonepileptic controls adds evidence to its epileptogenic role.

Gestural automatisms during syncope related to cervical malignancy

Cervical malignancies are a rare but well-known cause of syncope. Gestural automatisms during syncope have only rarely been reported. We describe a patient presenting with bimanual automatisms during syncopal episodes caused by parapharyngeal carcinoma involving the right laterocervical region. Ictal phenomenology was strongly suggestive of focal seizures and only video-polygraphic recording including EEG and ECG allowed the correct diagnosis to be established. Syncopal episodes ceased after partial removal of the mass. Although gestural automatisms in the context of a sudden spell with loss of consciousness are strongly suggestive of focal (mainly frontal or temporal) seizures, the diagnosis of syncope must be taken in account and confirmed or excluded by appropriate neurophysiological investigations.

Multiple watershed cerebral infarcts

The case of a 63-year-old female patient affected by arterial hypertension under home therapy, with disordered consciousness and confusion, is discussed. At the emergency department of another hospital she underwent cranial CT which showed mild swelling of right cerebral hemisphere. Based on the clinical suspicion of herpes simplex encephalitis compatible with a first MRI examination of the brain, the patient was admitted to the department of infectious disease of the polyclinic to confirm the diagnosis and plan the therapeutic approach. MRI was repeated and completed with EPI-DWI sequences and PRESS spectroscopy. It did not rule out categorically the infectious/inflammatory pattern but, based on a careful evaluation of the anatomic distribution of acute lesions, the most likely diagnostic hypothesis was the presence of multiple watershed cerebral infarcts on the right side.

Primary central nervous system lymphoma: role of DWI in the differential diagnosis

The case of a female patient admitted to the hospital for a syncopal episode characterized by mental confusion, retrograde amnesia, agnosia, lack of sphincter control and behavior disorders, is presented. Cranial CT showed a frontal bihemispheric lesion. MRI completed with DWI was then performed to better define the nature of the lesion and for an in-depth diagnostic study. The diagnostic role of conventional MRI combined with DWI and the importance of the latter in the differential diagnosis between primary central nervous system lymphoma (confirmed at histology) and glioblastoma multiforme is discussed.

Unusual lesion of the thalamic pineal region: role of conventional MRI and DWI in the differential diagnosis

The case of a 53-year-old female patient admitted to the Emergency department with symptoms from right third cranial nerve of acute onset, is presented. Cranial CT, performed in emergency, documented an intra-axial mass which required an in-depth diagnostic study with cranial MRI after contrast administration. Conventional MRI and DWI helped in correct lesion characterization and in the differential diagnosis with other brain disorders.

DWI and MR-spectroscopy in the differential diagnosis of focal brain lesions

The case of a patient with a previous history of cerebral infarction, shown to be positive for a brain neoformation on control CT, is presented. Subsequent MRI for an in-depth diagnostic study was completed with DWI and MR spectroscopy to define the nature of the lesion. The differential diagnosis of the lesion is discussed. In conclusion, the major diagnostic role of combined standard MRI with DWI sequences and MR-spectroscopy in the radiologic study of focal brain lesions, is stressed.

Usefulness of gait analysis for rehabilitation and follow-up in a patient with neurolupus. A case report

Neuropsychiatric symptoms are very common in patients with systemic lupus erythematosus (SLE) and can lead to a severe impairment of quality of life. Among neurological manifestations of SLE, altered gait patterns are common but usually not studied. Gait analysis allows us to evaluate the patients' skills, and in this way to plan a specific therapeutic-rehabilitative intervention. We describe the gait pattern of a patient with neurolupus, whose gait was characterized by a diminished propulsion capacity, a diminished load acceptance, a diminished progression of the pressure centre in a posterior-anterior sense, a diminished myoelectric activity in the swing and stence phases. We suggest that gait analysis may be a sensitive indicator of cerebral dysfunction and can be also an useful tool for the follow up of patients with neuropsychiatric SLE.