Organic schizophrenia, or schizophrenia-like syndrome is an important concern in psychiatry and various medical conditions and substances may be associated with it. Among them, Inborn Errors of Metabolism (IEM) are rare disease with interesting features : (i) some of them could be (or seems to be) presenting with schizophrenic psychiatric symptoms; (ii) when they are treatable, treatment leads to decrease schizophrenic symptoms; (iii) treatment is more efficient when beginning at early stage (i.e. before neurological or physical signs) and (iv) most psychiatrists have no specific knowledge about IEM. Moreover, IEM is a growing field in medicine because of improvement of biochemical and genetic techniques and new treatments are approved. Incidence is underestimated and psychiatric patients may be an at risk population. We propose a brief and comprehensive review of the literature focuses on treatable IEM with possible presenting psychiatric signs (Cerebrotendinous- Xanthomatosis, Wilson Disease, homocysteimia due to MTHFR deficiency, homocystinuria due to cystathionine beta-synthase deficiency, urea cycle disorders and Niemann Pick type C). We also present a simple diagnosis tool helping psychiatrist and caregivers in this field. The key objective is to devise a simple means of identifying patients with atypical psychiatric symptoms and to: (i) know when schizophrenic symptoms may be atypical and should draw our attention to organic disease, and IEM and (ii) learn which physical and neurological signs may trigger for each of the specific IEM. Looking for atypical signs of psychosis or minor physical signs may be extremely useful in rare cases of treatable disease.
