Recurrent de novo SPTLC2 variant causes childhood-onset amyotrophic lateral sclerosis (ALS) by excess sphingolipid synthesis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease of the upper and lower motor neurons with varying ages of onset, progression and pathomechanisms. Monogenic childhood-onset ALS, although rare, forms an important subgroup of ALS. We recently reported specific SPTLC1 variants resulting in sphingolipid overproduction as a cause for juvenile ALS. Here, we report six patients from six independent families with a recurrent, de novo, heterozygous variant in SPTLC2 c.778G>A [p.Glu260Lys] manifesting with juvenile ALS. METHODS: Clinical examination of the patients along with ancillary and genetic testing, followed by biochemical investigation of patients' blood and fibroblasts, was performed. RESULTS: All patients presented with early-childhood-onset progressive weakness, with signs and symptoms of upper and lower motor neuron degeneration in multiple myotomes, without sensory neuropathy. These findings were supported on ancillary testing including nerve conduction studies and electromyography, muscle biopsies and muscle ultrasound studies. Biochemical investigations in plasma and fibroblasts showed elevated levels of ceramides and unrestrained de novo sphingolipid synthesis. Our studies indicate that SPTLC2 variant [c.778G>A, p.Glu260Lys] acts distinctly from hereditary sensory and autonomic neuropathy (HSAN)-causing SPTLC2 variants by causing excess canonical sphingolipid biosynthesis, similar to the recently reported SPTLC1 ALS associated pathogenic variants. Our studies also indicate that serine supplementation, which is a therapeutic in SPTLC1 and SPTCL2-associated HSAN, is expected to exacerbate the excess sphingolipid synthesis in serine palmitoyltransferase (SPT)-associated ALS. CONCLUSIONS: SPTLC2 is the second SPT-associated gene that underlies monogenic, juvenile ALS and further establishes alterations of sphingolipid metabolism in motor neuron disease pathogenesis. Our findings also have important therapeutic implications: serine supplementation must be avoided in SPT-associated ALS, as it is expected to drive pathogenesis further.

Osteogénesis imperfecta de tipo III en niño ecuatoriano / Osteogenesis imperfecta type III in an Ecuadorian child

Introducción: la osteogénesis imperfecta es una rara enfermedad genética hereditaria caracterizada por su heterogeneidad causada por defectos del tejido conectivo con el rasgo de fragilidad ósea determinante de múltiples fracturas, incluso prenatales; deformidades de huesos largos y columna vertebral y otros síntomas extra-esqueléticos, como escleróticas de color azul, dentinogénesis imperfecta, trastorno de audición y afectación cardiovascular. Objetivo: Presentar un paciente con las características clínicas e imagenológicas de osteogénesis imperfecta de tipo III. Presentación del caso: Niño ecuatoriano de 4 años de edad de baja talla con antecedente de fracturas múltiples desde los 8 meses de nacido, con deformidad en columna vertebral demostrada por radiología por cifoescoliosis en forma de "S" y fracturas vertebrales, con deformidad progresiva en huesos largos; ha sufrido 16 fracturas, no deambula, sensorio presente, orientado en tiempo y espacio, desarrollo cognitivo normal para la edad. La fragilidad ósea del niño según el fenotipo clasifica al diagnóstico de tipo III de osteogénesis imperfecta, el cual es progresivo e invalidante por las deformidades óseas y múltiples fracturas demostradas en exámenes imagenológicos, sin modificaciones en el color de escleróticas, de herencia presumiblemente dominante. Conclusiones: La descripción clínica y radiológica de osteogénesis imperfecta, afección poco conocida, correspondiente al fenotipo III de la enfermedad, reportada en niño ecuatoriano de 4 años de edad, con talla baja que no deambula, expresión de la severidad de su afección genética, con severas alteraciones óseas por su fragilidad con fracturas múltiples en huesos largos y vértebras(AU)

Introduction: Osteogenesis imperfecta is a rare hereditary genetic disease characterized by its heterogeneity caused by connective tissue defects with the feature of bone fragility determining multiple fractures, even prenatal ones; also deformities of long bones and spine, and other extra-skeletal symptoms, such as blue sclerotic, dentinogenesis imperfecta, hearing disorder and cardiovascular affectations. Objective: To present a patient with clinical and radiological findings of osteogenesis imperfect type III. Case presentation: Ecuadorean male child of 4 years old, with a short height, history of multiple fractures from 8 months of age, with spinal deformity demonstrated by radiology due to "S" shaped kyphoscoliosis and vertebral fractures, with progressive deformity in long bones. The boy has suffered 16 fractures, he does not wander, and he is sensory present, oriented in time and space, with normal cognitive development for his age. The bone fragility of the child according to the phenotype classifies in the type III diagnosis of osteogenesis imperfecta, which is progressive and invalidating due to bone deformities and multiple fractures evidenced in imaging tests, without changes in the color of sclerotics and of presumably dominant inheritance. Conclusions: The clinical and radiological description of osteogenesis imperfecta, which is little-known pathology, corresponding to type III phenotype is reported in a 4-year-old boy who, due to his involvement, has a short height and does not wander as a consequence of the severity of bone affectations with fractures in long bones and vertebrae, mainly produced by the fragility of the bones due to his genetic disease(AU)