Amino-acid disorders including phenylketonuria and MSUD — branching viva

Opening framework

My framework has four layers. First, the recognition — a neonate well at birth then deteriorating 48 to 120 hours into feeds with ketoacidosis, a maple-syrup odour and a normal ammonia is maple syrup urine disease until proven otherwise, and the quantitative amino acids decide it. Second, the shared mechanism — each aminoacidopathy is an autosomal-recessive block that allows a neurotoxic or tissue-toxic metabolite to accumulate, which is why the management always restricts the precursor and clears the toxin. Third, the acute protocol — switch off catabolism, give disease-specific formula, and dialyse at threshold. Fourth, the family — a 25 percent recurrence risk, carrier testing, and reproductive options, with maternal PKU as the special case where the mother's metabolite injures a genetically normal fetus. ^{[1] [7]}