PIGG variant pathogenicity assessment reveals characteristic features within 19 families.

PURPOSE: Phosphatidylinositol Glycan Anchor Biosynthesis, class G (PIGG) is an ethanolamine phosphate transferase catalyzing the modification of glycosylphosphatidylinositol (GPI). GPI serves as an anchor on the cell membrane for surface proteins called GPI-anchored proteins (GPI-APs). Pathogenic variants in genes involved in the biosynthesis of GPI cause inherited GPI deficiency (IGD), which still needs to be further characterized. METHODS: We describe 22 individuals from 19 unrelated families with biallelic variants in PIGG. We analyzed GPI-AP surface levels on granulocytes and fibroblasts for three and two individuals, respectively. We demonstrated enzymatic activity defects for PIGG variants in vitro in a PIGG/PIGO double knockout system. RESULTS: Phenotypic analysis of reported individuals reveals shared PIGG deficiency-associated features. All tested GPI-APs were unchanged on granulocytes whereas CD73 level in fibroblasts was decreased. In addition to classic IGD symptoms such as hypotonia, intellectual disability/developmental delay (ID/DD), and seizures, individuals with PIGG variants of null or severely decreased activity showed cerebellar atrophy, various neurological manifestations, and mitochondrial dysfunction, a feature increasingly recognized in IGDs. Individuals with mildly decreased activity showed autism spectrum disorder. CONCLUSION: This in vitro system is a useful method to validate the pathogenicity of variants in PIGG and to study PIGG physiological functions.

Thiamine Pyrophosphokinase Deficiency due to Mutations in the TPK1 Gene: A Rare, Treatable Neurodegenerative Disorder.

TPK deficiency due to TPK1 mutations is a rare neurodegenerative disorder, also known as thiamine metabolism dysfunction syndrome 5 (OMIM no.: 614458). Here, we report a new patient with compound heterozygous TPK1 mutations, of which one has not been described so far. The individual reported here suffered from acute onset encephalopathy, ataxia, muscle hypotonia, and regression of developmental milestones in early infancy, repeatedly triggered by febrile infections. Initiation of high-dose thiamine and magnesium supplementation led to a marked and sustained improvement of alertness, ataxia, and muscle tone within days. Contrary to the described natural history of patients with TPK deficiency, the disease course was favorable under thiamine treatment without deterioration or developmental regression during the follow-up period. TPK deficiency is a severe neurodegenerative disease. This case report demonstrates that this condition is potentially treatable. High-dose thiamine treatment should therefore be initiated immediately after diagnosis or even upon suspicion.

Pontocerebellar Hypoplasia: a Pattern Recognition Approach.

Pontocerebellar hypoplasias (PCH) represent a heterogeneous group of very rare disorders with reduced volume of pons and cerebellum. The term is purely descriptive and does not imply a genetic progressive disease. Currently (as of Jan 01, 2020), 13 different types are listed in OMIM (Online Mendelian Inheritance in Man), associated with 19 different genes. However, a large group of similar imaging patterns is known, and it is unclear why some are labeled as PCH, while others are not. The latter include CASK- and VLDLR-associated disorders, some tubulinopathies, certain dystroglycanopathies, a few congenital disorders of glycosylation (CDG) syndromes, several forms associated with rare variants (e.g., DCK1, WDR81, ITPR1), and "cerebellar disruption of prematurity"-an acquired etiology. The objective of this paper is to elaborate a pattern recognition approach, mainly imaging-based, to facilitate a timely and accurate diagnosis, to narrow the differential diagnosis, and to enable targeted additional (genetic) investigations. We describe magnetic resonance imaging (MRI) findings and offer "checklists" for infratentorial findings (e.g., non-lobulated vermis, dragonfly pattern of the cerebellum, cerebellar cysts, brainstem kinking, longitudinal grooves along the brainstem, flat pons) as well as for supratentorial anomalies (e.g., agenesis of corpus callosum, optic atrophy, simplified gyral pattern, and hypomyelination). The clinical context and laboratory investigations need to be considered as well. We also provide a "checklist" for clinical features. A systematic analysis of imaging and clinical features can assist in narrowing the differential diagnosis and permitting more targeted genetic testing. Some imaging patterns are diagnostic.

Evaluation of real-life outcome data of patients with spinal muscular atrophy treated with nusinersen in Switzerland.

Spinal muscular atrophy (SMA) is an autosomal recessive disorder causing progressive proximal muscular, respiratory, and bulbar weakness. We present outcome data on motor function, ventilation, nutrition, and language development of SMA patients treated with nusinersen in Switzerland. This multicenter, observational study included 44 patients. At treatment initiation, after 2 months and then every 4 months we assessed motor function with the Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND), Hammersmith Functional Motor Scale expanded (HFMSE) and 6-Minute Walk Test (6MWT). At treatment initiation, patients were 0.1-44.6 years old, treatment duration ranged from 6 to 41 months. All 11 SMA type 1 children achieved higher CHOP-INTEND scores at the last assessment compared to treatment initiation, 4 acquired stable sitting. Six type 1 children were <18 months-old at treatment initiation. Two of them did not need ventilation or nutritional support at the last assessment; three had delayed language development and 3 articulation difficulties. 5/21 SMA type 2 patients achieved higher HFMSE scores. All ambulant type 3 patients showed a gain in the 6MWT. Nusinersen is an effective treatment, with gains in motor function occurring particularly in children and SMA type 1, but also in type 2 and 3, adolescents and adults.

Chapeau de gendarme in a toddler points to focal epilepsy originating from the subcentral gyrus.

The chapeau de gendarme sign or ictal pouting has been associated with focal epilepsy of frontal origin. The identification and characterization of this semiologic feature derive mainly from adult epilepsy surgery series, whereas paediatric cases have rarely been reported. Here, we present a 14-month-old girl with a chapeau de gendarme sign with eyes closed as the sole initial manifestation of left frontal lobe epilepsy. Brain MRI revealed an area suspicious for focal cortical dysplasia in the anterior aspect of the left subcentral gyrus, and ictal scalp EEG supported a seizure onset correlating with the lesion. This is the youngest reported patient with a chapeau de gendarme sign and the first to be associated with a lesion in the subcentral gyrus. Our observation extends the age range of patients presenting with this intriguing semiology and the range of localizations where it may originate. We propose considering the chapeau de gendarme sign as a hallmark of focal epilepsy in all age groups, including early life, and that presurgical evaluation should be timely initiated in patients with refractory seizures. [Published with video sequence].

Etiology of Carpal Tunnel Syndrome in a Large Cohort of Children.

(1) Background: Carpal tunnel syndrome (CTS), a compressive mononeuropathy of the median nerve at the wrist, is rare in childhood and occurs most frequently due to secondary causes. (2) Methods: Medical history, electrodiagnostic findings, and imaging data of patients with CTS from two pediatric neuromuscular centers were analyzed retrospectively. The etiology of CTS was investigated and compared with the literature. (3) Results: We report on a cohort of 38 CTS patients (n = 22 females, n = 29 bilateral, mean age at diagnosis 9.8 years). Electrodiagnostic studies of all patients revealed slowing of the antidromic sensory or orthodromic mixed nerve conduction velocities across the carpal tunnel or lack of the sensory nerve action potential and/or prolonged distal motor latencies. Median nerve ultrasound was diagnostic for CTS and confirmed tumorous and vascular malformations. Etiology was secondary in most patients (n = 29; 76%), and mucopolysaccharidosis was the most frequent underlying condition (n = 14; 37%). Idiopathic CTS was rare in this pediatric cohort (n = 9; 24%). (4) Conclusion: Since CTS in childhood is predominantly caused by an underlying disorder, a thorough evaluation and search for a causative condition is recommended in this age group.