Disorders of Amino Acid Metabolism Flashcards Preview

Inborn Errors Of Metabolism > Disorders of Amino Acid Metabolism > Flashcards

Flashcards in Disorders of Amino Acid Metabolism Deck (6)
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PKU

- PAH Defect
or biopterin deficiency: required for PAH function
- Can't convert phenylalanine >> tyrosine
- AR
- High phenylalanine >> eczema, hypopigmentation, seizures, limb spasticity. MOUSY URINE ODOR, MR
- phenylalanine restricted diet, biopterin supplement

1

Tyrosinemia

- 5 types
- Type I: FAH deficiency
- metabolite accumulation >> LIVER FAILURE with early failure of SYNTHETIC FUNCTION, hypophosphatemic rickets, FTT, parenthesis, seizures, paralysis
- restrict tyrosine and phenylalanine in diet, liver transplant, NTBC (block further upstream >> build-up off less toxic metabolites
- Type II: tyrosine aminotransferase deficiency >> tyrosine/phenolic acid accumulation
- OCULOCUTANEOUS: photophobia, corneal ulceration, crusted hyperkeratotic skin lesions (palms/soles), seizures, developmental delay

2

MSUD

BCKD complex activity deficiency
accumulation of BCAA's: leucine, isoleucine, valine
*leucine is NEUROTOXIC
Severe: lethargy, emesis, hypotonia, seizures- infancy
Intermediate: neuro decompensation during stress- child/adulthood
Chronic Progressive: gradual neuro dz (szrs, developmental delay)
*ammonia, lactate, bicarb often normal

3

Homocystinuria

cystathionine beta-synthase deficiency
AR
homocysteine can't >> cystathionine
requires cofactor pyridoxine
Sx: MR, eye lens dislocation, MARFANOID BODY HABITUS, osteoporosis, acute vascular THROMBOSIS (50% by 30yo if untx)
Tx: 50% respond to pyridoxine (B6); limit METHIONINE in diet, extra cystine in diet, betaine (donates methyl to convert homocysteine to methionine instead of cystathionine)

4

NKH: non-ketotic hyperglycinemia

glycine cleavage defect
Classic: lethargy, apnea, hypotonia, seizures in NB
EEG: BURST SUPPRESSION pattern
If survive >> spastic CP
Late Onset: neurologic sx
Diagnosis: CSF : plasma glycine ratio > 0.08
no ketosis, acidosis
Tx: NaBenzoate, DM - reduce seizures, improve arousal
NO depakote - raises CSF glycine levels

5

Alkaptonuria

homogentisate 1,2-dioxygenase deficiency
Hyperpigmentation: dark sclerae, ear cartilage, cerumen, urine
Arthritis in adults
Heart dz >> MI