Abstract
Detecting psychiatric disorders of secondary origin is a crucial concern for the psychiatrist. But how can this reliably be done among a large number of conditions, most of which have a very low prevalence? Metabolic screening undertaken in a population of subjects with psychosis demonstrated the presence of treatable metabolic disorders in a significant number of cases. The nature of the symptoms that should alert the clinician is also a fundamental issue and is not limited to psychosis. Hereditary metabolic disorders (HMD) are a rare but important cause of psychiatric disorders in adolescents and adults, the signs of which may remain isolated for years before other more specific organic signs appear. HMDs that present purely with psychiatric symptoms are very difficult to diagnose due to low awareness of these rare diseases among psychiatrists. However, it is important to identify HMDs in order to refer patients to specialist centres for appropriate management, disease-specific treatment and possible prevention of irreversible physical and neurological complications. Genetic counselling can also be provided. This review focuses on three HMD categories: acute, treatable HMDs (urea cycle abnormalities, remethylation disorders, acute intermittent porphyria); chronic, treatable HMDs (Wilson’s disease, Niemann-Pick disease type C, homocystinuria due to cystathionine beta-synthase deficiency, cerebrotendinous xanthomatosis); and chronic HMDs that are difficult to treat (lysosomal storage diseases, X-linked adrenoleukodystrophy, creatine deficiency syndrome). We also propose an algorithm for the diagnosis of HMDs in patients with psychiatric symptoms.
Highlights
Detecting psychiatric disorders of secondary origin is a crucial concern for the psychiatrist
How can this reliably be done among a large number of conditions, most of which have a very low prevalence? A study performed some time ago [1] involving a sample of 658 patients who had a psychiatric consultation with a complete clinical evaluation and full investigations showed that 9.1% of these patients had a physical condition that presented with psychiatric symptoms
Treatments are available for some Hereditary metabolic disorders (HMD), which we focus on in this article (Table 1)
Summary
Detecting psychiatric disorders of secondary origin is a crucial concern for the psychiatrist. GM2 gangliosidosis presents with neurological disorders (peripheral motor involvement, cerebellar ataxia or dystonia) associated with psychiatric signs in 20%–40% of cases (e.g. acute psychotic disorder, hallucinations, depressive syndrome) [48,49,50] These signs may remain isolated for years before the appearance of neurological signs but can appear later. If atypical symptoms are present, a simple diagnostic algorithm should comprise the following: firstrank symptoms (visual hallucinations, mental confusion, catatonia, fluctuation of symptoms, unusual (or paradoxical) response to treatment, progressive cognitive change) associated with second-rank symptoms (early onset, acute onset, intellectual impairment, lack of treatment efficacy) which may aid the psychiatrist in detecting an HMD [59] Screening for these diseases is very specific and requires specialist advice (Figure 2). The management of psychotic disorders must always be accompanied by a specific work-up
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