Objectives: Emphasize the need to search, in different evolutive moments, the etiology of psychomotor development deviations to distinguish the chronic non-progressive  encephalopathies from the progressive ones through the description of a late diagnosis of a Niemman-Pick type C disease (NPC) with a previous diagnosis of chronic non-progressive encephalopathy.

Case report: JPPP, male, 3 years old, first presented with motor development delay, followed by a delay in language acquisition. A MRI in 2011 suggested CMV lesion and two USG in the same year appeared normal. Follow up showed progressive motor losses and worsening of cognition. New investigation in 2012, revealed vertical supranuclear gaze palsy, ataxia, eventual dysphagia and splenomegaly. Bone marrow aspiration showed crinkled-paper cytoplasm cells, questioning Gaucher disease. As the enzymatic test was negative and the patient evolved with gelastic cataplexy, it was initiated the research to NPC with a Niemman-Pick suspicion index (NP-SI) of 142 points. The hypothesis was confirmed by a positive Filipin test. In June/2013 Miglustat was initiated as substrate reduction therapy, and imipramine to cataplexy.

Conclusion: NPC is rare and polimorphic making it difficult to diagnose, specially when the visceral signs present themselves later. The use of the Niemman-Pick suspicion index oriented the investigation and helped in the case elucidation. This case makes clear that systematization is essential for the differential diagnosis of the psychomotor development delays.