Myosin Vb (MYO5B) is a motor protein that facilitates protein trafficking and recycling in polarized cells by RAB11- and RAB8-dependent mechanisms. Biallelic MYO5B mutations are identified in the majority of patients with microvillus inclusion disease (MVID). MVID is an intractable diarrhea of infantile onset with characteristic histopathologic findings that requires life-long parenteral nutrition or intestinal transplantation. A large number of such patients eventually develop cholestatic liver disease. Bi-allelic MYO5B mutations are also identified in a subset of patients with predominant early-onset cholestatic liver disease. We present here the compilation of 114 patients with disease-causing MYO5B genotypes, including 44 novel patients as well as 35 novel MYO5B mutations, and an analysis of MYO5B mutations with regard to functional consequences. Our data support the concept that (1) a complete lack of MYO5B protein or early MYO5B truncation causes predominant intestinal disease (MYO5B-MVID), (2) the expression of full-length mutant MYO5B proteins with residual function causes predominant cholestatic liver disease (MYO5B-PFIC), and (3) the expression of mutant MYO5B proteins without residual function causes both intestinal and hepatic disease (MYO5B-MIXED). Genotype-phenotype data are deposited in the existing open MYO5B database in order to improve disease diagnosis, prognosis, and genetic counseling.

Patients with mutations in the polymerase gamma gene (POLG) may present with progressive ataxia and in such situations neuroimaging findings may suggest the diagnosis. Herein we report a patient with a POLG gene W748S homozygous mutation and characteristic lesions in the thalamus, cerebellum and inferior olivary nucleus seen on magnetic resonance imaging.

Introducción: La atrofia muscular espinal (AME) es una enfermedad degenerativa que afecta las neuronas motoras del asta anterior de la médula espinal, se manifiesta por debilidad muscular progresiva de predominio proximal, hipotonía y arreflexia osteotendinosa, la etiología es una mutación en el gen de supervivencia neuronal SMN. Objetivo: determinar las características clínicas de los pacientes menores de 18 años con atrofia muscular espinal en de Medellín, durante el período 2008-2013. Materiales y métodos: se realizó un estudio descriptivo retrospectivo de los pacientes con AME que consultaron en el Hospital Universitario San Vicente Fundación y un consultorio privado de neuropediatría en Medellín durante el período 2008-2013, en total se recopilaron datos de 29 pacientes, se revisaron las características clínicas, las ayudas diagnósticas practicadas y los tratamientos realizados. Resultados: la AME tipo II resultó la forma clínica más frecuente (62%) seguida por la AME tipo I (24.13%), las principales manifestaciones fueron la hipotonía (100%) debilidad muscular (93.1%) y la arreflexia osteotendinosa (82.8%). Las fasciculaciones en la lengua se presentaron en el 48.3% de los pacientes. La prueba molecular fue realizada en 6 pacientes y en todos se encontró deleción del exón 7 del gen SMN1. Conclusión: la atrofia muscular espinal es una enfermedad degenerativa y de progresión variable de acuerdo a su clasificación. Clínicamente, se debe sospechar cuando exista síndrome motoneuronal y fasciculaciones linguales. El diagnóstico molecular es el método más acertado para confirmar la enfermedad.

Patients with mutations in tubulin-related genes usually present with brain malformations, intellectual disability, epilepsy, microcephaly and ocular abnormalities. In these patients the diagnosis can be suggested by neuroimaging findings. We report a 5-year-old patient with characteristic magnetic resonance imaging findings including malformation of cortical development, fused basal ganglia, large head of the caudate nuclei, absent anterior limbs of the internal capsules, corpus callosum dysgenesis and dysplastic cerebellar vermis. Sequencing of the TUBB2B gene confirmed a heterozygous mutation: c. 260C>A (p. Pro87Gln).

Colombia has a high prevalence of mucopolysaccharidosis (MPS) type IVA. Nevertheless, data regarding the mutation spectrum for MPS IVA in this population have not been completely characterized. Forty-seven families and 53 patients from seven different Colombian regions were tested for MPS IVA mutations. We compared the sequences with the N-acetylgalactosamine-6-sulfatase (GALNS) reference sequence NM_000512.4, and gene variants were reported. Bioinformatics analysis was performed using SWISS-MODEL. The mutant proteins were generated by homology from the wild-type GALNS 4FDJ template obtained from the PDB database, and visualization was performed using Swiss-PDBViewer and UCSF Chimera. The predictive analysis was run using different bioinformatic tools, and the deleterious annotation of genetic variants was performed using a neural network. We found that 79% and 21% of the cohort was homozygous and compound heterozygous, respectively. The most frequent mutation observed was p.Gly301Cys (78.3% of alleles), followed by p.Arg386Cys (10.4% of alleles). A novel mutation (p.Phe72Ile) was described and classified in silico as a pathogenic variant. This study reveals the mutation spectrum of MPS IVA in Colombia. The high prevalence of the p.Gly301Cys mutation suggests a founder effect of this variant in the Colombian population that causes diseases in the Andean region (via migration). These data can facilitate genetic counseling, prenatal diagnosis, and the design of therapeutic interventions.