Pourquoi s'intéresser à la maladie de Niemann Pick de type C quand on est psychiatre d'enfant et d'adolescent?

Background: Searching for organic condition, including inborn errors of metabolism (IEM), in every patient with psychiatric symptoms is part of the healthcare program. Given the prevalence of schizophrenia around 1% of general population, searching for organic schizophrenia is an important concern in psychiatry as various medical conditions and substances may be associated with it. Method: After a brief presentation of inborn errors of metabolism (IEM) in general and those with possible presenting psychiatric signs, we will take the example of Niemann Pick type C (NPC) and present a literature review of psychiatric symptoms (mainly schizophrenia-like) in this severe disease newly treatable. At last, we will present a simple diagnosis tool helping psychiatrist and caregivers in this field. The key objective is to: (i) know when schizophrenic symptoms may be atypical and should draw our attention to organic disease, and NPC and (ii) learn which physical and neurological signs may trigger for each of the specific IEM, including NPC. Results: Incidence of IEM is underestimated, and patients showing early psychotic signs and intellectual regression may be at risk population. NPC, like other IEM, is a rare disease with interesting features: (i) many patients can present with schizophrenic like symptoms; (ii) treatment is more efficient when beginning at early stage (i.e. before neurological or physical signs) and (iii) most psychiatrists have no specific knowledge about NPC, or IEM. To detect patients, our algorithm distinguishes the first order of atypical psychiatric symptoms (e.g. catatonia; visual hallucinations) from the second order (e.g. early or acute onset, intellectual deficiency). The second order of symptoms needs to be associated with first order of symptoms to be considered atypical. Conclusion: Looking for atypical signs of psychosis or minor physical signs may be extremely useful in rare cases of treatable disease and may lead to diagnoses and early treatment.