Evaluación neuropsicológica de un adulto colombiano diagnosticado con Síndrome de Morquio B / Neuropsychological assessment of a Colombian adult diagnosed with Morquio B Syndrome

Resumen El síndrome de Morquio B es una enfermedad rara y de baja prevalencia, por lo cual poco se ha estudiado sobre el funcionamiento neuropsicológico y estado cognitivo de quienes lo padecen. Este estudio de caso presenta los resultados del funcionamiento en atención, memoria, lenguaje, gnosias, praxias y funciones ejecutivas de un adulto colombiano diagnosticado con este síndrome. Se encontró que el paciente puede adquirir nuevo conocimiento; muestra memoria visoespacial y de trabajo verbal conservadas; repite, lee y escribe información sencilla que es conocida para él; sigue órdenes simples a partir de comandos verbales; muestra habilidades viso perceptuales y grafomotoras; tiene un desarrollo normal de pensamiento abstracto y asociativo, y es capaz de planear y solucionar problemas. Sin embargo, presenta dificultades en atención visual sostenida, atención audio-verbal, velocidad de procesamiento, lenguaje comprensivo, repetición y escritura al dictado de frases completas, flexibilidad cognitiva, y fluidez verbal semántica y fonológica. Se discute como factores más relevantes del funcionamiento cognitivo del paciente la relación entre el síndrome de Morquio B y la gangliosidosis GM1, y la falta de entrenamiento en el manejo de información de alta complejidad, dada su condición de desescolarización.

Abstract Since Morquio B syndrome is a low-prevalence rare disease, scarce evidence about neuropsychological functioning and cognitive status in diagnosed people is known. This case study shows the results of functioning in attention, memory, language, gnosias, praxias, and executive functions in a Colombian man diagnosed with this syndrome. It was found that the patient is capable of acquiring new information and exhibits preserved visuospatial and verbal working memory; he is also able to repeat, read and write simple information as long as it is familiar to him, and is capable of following simple verbal instructions with no difficulty; moreover, he displays preserved visuospatial and graphomotor abilities, has a normal development of abstract and associative thinking, and is able to plan and solve problems. Nonetheless, he exhibits difficulties in audio-verbal and sustained visual attention, as well as in processing speed, comprehensive language, repetition and writing of complete phrases, cognitive flexibility, and semantic and phonological verbal fluency. It is discussed the association between Morquio B syndrome and gangliosidosis GM1 as well as the lack of training in the management of highly complex information due to unschooling of this patient as the two most relevant factors of his cognitive functioning.

β-Galactosidase Deficiency in Colombia: Report of 20 Patients Detected Using Dried Blood Spot Samples

Abstract β-Galactosidase (BGal) is the first enzyme involved in the catabolism of sphingolipids. Two pathologies have been directly associated with its deficiency: GM1 gangliosidosis and Morquio B. Morquio B is among the rarest types of mucopolysaccharidosis (MPS). We aim to document the β-galactosidase deficiency in Colombia. We evaluated leukocytes from 1492 healthy Colombian individuals and 923 patients, referred between 2005 and August 2014. Dried blood spot (DBS) samples from the same number of patients were evaluated. β-Galactosidase was measured with 4-methylumbelliferyl-β-d-galactoside. As a control enzyme, the total hexosaminidase activity was also evaluated. We identified 14 patients with GM1 gangliosidosis, 5 patients with Morquio B, and 1 patient with I-cell disease. We could establish a reference value for Bgal in Colombian leukocyte samples. GM1 gangliosidosis is the main pathology associated with a direct deficiency of BGal. The high number of patients found with MPS IVB indicates that there are patients who could be misdiagnosed due to an unawareness of the disease.