Metabolic Errors present itself at different stages of a child's life, depending upon its severity. Inborn errors of metabolism (IEM) are sometimes referred to as "silent killers" because they can strike healthy-appearing full-term infants without warning. The signs of IEM present at birth, can be subtle, difficult to detect or easy to mistake for other more common neonatal pathologies. It requires a high index of suspicion to include an IEM in the differential diagnosis of an initially healthy full-term baby who begins to display hypoglycemia or poor feeding. temperature instability. At such times an IEM is usually considered. 

In general when multiple organs are getting affected, we need to think of an underlying cause that unites it all and needs to suspect metabolic errors.

Several groups of inherited metabolic disorders most notably the organic acidemias, urea cycle defects and certain disorders of amino acid metabolism typically present with life threatening symptoms of encephalopathy (injury/ inflammation of the brain). These symptoms are the result of toxic effects of accumulating metabolites on the Central Nervous System (CNS).

1. Neonate

   Symptoms for inborn errors of metabolism of substrate and intermediary metabolism develop once a significant amount of toxic metabolites accumulate following the initiation of feeding and may include the following: poor feeding vomiting, diarrhea, and/or dehydration; temperature instability; tachynpnea; apnea; bradycardia; poor perfusion; irritability; involuntary movement; posturing; abnormal tone; seizures; and altered level of consciousness and May be associated with an increased risk of sepsis.  Neonates with inborn errors of substrate and intermediary metabolism, the physical examination findings are usually unremarkable.

   For inborn errors of metabolism (IEMs) of energy deficiency, symptoms usually develop within 24 hours of birth and are often present at birth. Neonates with inborn errors that result in defects in energy production and use also often have dysmorphic features, skeletal malformations, cardiopulmonary compromise, organomegaly and severe generalized hypotonia.
   

2. Infants

   Recurrent episodes of vomiting, ataxia, seizures, lethargy, coma, fulminant hepato-encephalopathy or a combination.

   Dysmorphic or coarse features, skeletal abnormalities and abnormalities of the hair or skin. 

   Poor feeding, failure to thrive.

   Dilated or hypertrophic cardiomyopathy, hepatomegaly, jaundice and liver dysfunction.

   Developmental delay, occasionally with loss of milestones.
   
   Ataxia, hypotonia or hypertonia and visual and auditory disturbances.

3. Children, adolescents, and adults
   
   Common findings include mild to profound mental retardation, autism, learning disorders, behavioral disturbances, hallucinations, delirium, aggressiveness, agitation, anxiety, panic attacks, seizures, dizziness, ataxia, exercise intolerance, muscle weakness.

   Some manifestations may be intermittent, precipitated by the stress of illness, changes in diet, exercise and/or hormones, or progressive with worsening over time.