Mucopolysaccharidosis IIIB is a lysosomal disease characterized by a severe neurological deterioration, the pathophysiological mechanisms of which are poorly understood. Recently FGF pathway was shown to be altered leading us to explore a downstream target involved in brain development: the collapsin response mediator protein-1 (CRMP-1). CRMP-1 transcript level was normal but a cleavage of CRMP-1 was observed with an abnormal expression of the truncated form until adult age. This truncated CRMP-1 protein could play a role in post-natal cortex maturation and be involved in neuronal alterations occurring in lysosomal diseases.