Inherited errors of metabolism that may present with psychiatric complaints include:
(1) porphyria (see previous section)
(2) urea cycle disorders
(3) organic acidurias
(4) maple sugar urine disease (MSUD)
(5) methylene tetrahydrofolate reductase (MTHFR) deficiency
(6) phenylketonuria (PKU)
(6) disorders of biopterin metabolism
(7) Tay-Sachs (late infantile form of GM2 gangliosidosis), neuronal ceroid lipofuscinosis and other storage diseases
(8) disorders of mitochondrial DNA
(9) Wilson's disease
Psychiatric problems may include:
(1) confusion or dementia
(2) delirium
(3) depression
(4) anxiety or phobias
(5) mania or hypomania
(6) psychosis or schizophrenia (hallucinations, etc)
(7) irritability or aggressiveness
(8) disinhibition
(9) catatonia
(10) emotional lability or behavioral problems
(11) autism
(12) agitation
(13) obsessive-compulsive disorder
The psychiatric symptoms may present prior to recognition of an underlying metabolic disorder. A patient with an undiagnosed metabolic disorder may be mislabeled and mismanaged.
When to consider an inborn error of metabolism:
(1) family history of an inherited metabolic disorder
(2) resistance to standard therapy (a particular problem for porphyria since some psychotropic drugs may trigger a porphyric attack)
(3) nonpsychiatric clinical findings that are progressive and/or multisystemic
(4) concurrent neurologic problems such as mental retardation or developmental delays
(5) regression from past levels of performance
(6) concurrent ophthalmologic defects
