which trinucleotide repeat?

19yo, unsteady since about 13, getting worse.

no vibration sense in her toes
areflexic at knees and ankles
plantars upgoing
scoliosis
echo shows concentric LVH

which trinucleotide repeat?

A. CAG
B. CTG
C. CGG
D. GAA

Areflexia sitting next to upgoing plantars is what should stop you here. A
lower motor sign and an upper motor sign together, in a young person with
sensory ataxia, narrows this fast. Add the scoliosis, add diabetes in about
a third of them, add the cardiomyopathy that ends up being what kills them,
and youre looking at Friedreich ataxia.

It behaves differently from the repeat diseases u learned first. The
expansion sits in an intron of FXN, so the gene gets silenced and frataxin
falls. Loss of a protein, inherited recessively, which is why theres usually
no family history to find. The CAG diseases build a toxic protein instead and
run dominant.

so, placed it? its D. GAA in FXN, frataxin drops, mitochondrial iron handling
fails and the long tracts and the myocardium go first.

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