Introduction: Cataplexy is a brief episode of bilateral loss of muscle tone with intact consciousness, triggered by a variety of strong emotions such as anger, laugh, humor or surprise and it is considered to represent the physiologic atonia of rapid eye movement sleep. However, Niemann-Pick disease type C (NPC) is an inherited lipid storage disorder, characterized by a defect in intracellular trafficking of exogenous cholesterol that leads to the lysosomal accumulation of unesterified cholesterol. The aim of this report is to demonstrate a patient who presenting of gelastic cataplexy, is get a diagnosis NPC.

Case Description: A 5-year-old boy presented to our hospital with a 3,5-year history of fall attacks triggered by laughing, leading to a generalized loss of muscle tone without loss of consciousness. The boy has reciped to ataxia, moderate cognitive impairment and vertical gaze palsy for 3 years. The boy has hepatosplenomegali. These signs are ledaded us NPC. We showed the cataplexy with polysomnography. We do the patient bone marrow aspiration. The foam cell was seen.

Result: We were molecularly diagnosed as NPC1 homozygous mutation, diagnostic of NPC.

Conclusion/Discussion:

Gelastic cataplexy is rarely described as the first neurologic symptom.  Children with very frequent cataplexy should be tested early for NPC.