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Inborn errors of metabolism (Clinical presentation (Faltering growth,…
Inborn errors
of metabolism
Pathophysiology
Energy metabolism
Mitochondrial diseses e.g. MELAS, MERRF, Alpers
Fatty acid oxidation e.g. carnitine transporter deficiency
Glycogen storage diseases e.g. McArdle disease
Lipid metabolism e.g. familial hypercholesterolemia, Fabry, Gaucher,
Niemen-Pick type C, Wolman disease
Organelle disorder
Lysosomes (mucopolysaccharidoses) e.g. Hurler, Hunter, Sanfillipo, Morquio, Maroteaux-Lamy
Peroxisomes e.g. Zellweger syndrome
Toxic metabolites
Accumulation o f a metabolite
Amino acids e.g. homocysteinuria
Urea cycle e.g. citrullinemia
Organic acids e.g. isovaleric acidemia
Carbs e.g. galactosaemia
Clinical
presentation
Faltering growth
Seizures
Developmental regression
Dysmorphic features
Diagnosis
Examination
Abdo exam
Hepatosplenomegaly
Neuro exam
Seizures, reduced IQ
Drowsiness, irritability, coma
Developmental exam
Regression/loss of skills
Developmental delay
Cardio exam
Displaced apex (cardiomegaly)
Investigations
Bloods
ABG (acidosis if excess organic acid alkalosis), FBC, U+E, LFT
(may be deranged), glucose (may have hypos)
Metabolic screen (AAs, ammonia, FAs, white cell enzymes, lactate)
Genetic screen
Bedside
Obs
Urine
Metabolic screen (AAs, organic acids, GAGs)
History
DH
Meds, allergies
PMH
Growth and development
Known medical conditions
Newborn screening results
PC/HPC
Non-specific e.g. dysmorphism, developmental delay,
faltering growth, seizures, unexplained acidosis/alkalosis
FH
Any IEMs
SH
Living arrangements, nursery/school,
social support
Management
Conservative
Information, advice, support
Low protein diet (IA, homocyst, MSUD)
Phenylalanine restriction (PKU)
Special diet and avoid fasting (MCAD, GA1)
Medical
Specific
Ammonia scavangers
Enzyme replacement
E.g.
Symptomatic
AEDs
Analgesia
Screening
Newborn blood tests
CF, haemaglobinopathies, hypothyroidism,
6 IEMs (PKU, MCAD, MSUD,
GA1, isvoleric acidemia, homocysteinuria)
Definition
Disorders of enzyme reactions
involved in synthesis, conversion
or degradation of molecules
Epidemiology
Individually rare,
collectively common
Usually AR inheritance