Friedrich's ataxia, FARR, LOFA, VLOFA

Friedrich's ataxia (AR) is subclassified into classical (75%), FARR (FA with retained reflexes, adult onset), LOFA (late onset FA) and VLOFA (very late onset FA). 
In FA, pathology involves spinocerebellar tracts, lateral corticospinal tracts, posterior columns but NOT cerebellum.  Clinical features include a.  progressive gait ataxia and scoliosis  b.  gait worse in darkness (posterior column involvement)  and worsening during puberty    c.  dysarthria and hand incoordination   d.  areflexia  e. extensor plantars.  Associated features may include  e.  optic nerve atrophy (25%),  f.  SN hearing loss (10%)  g.  optic flutter or square wave jerks but not opthalmoplegia  h.  hypertrophic cardiomyoapthy (90%)  i. pes cavus  j. diabetes mellitus in 15 % 15 years after onset  j.  wheelchair bound after 15 years  k.  Death 30-70.
In FARR, LOFA, VLOFA, sporadic ataxia occurs without cardiomyopathy. Spasticity occurs, areflexia does not.  Again normal cerebellum.  Sporadic ataxia patients may warrant gene testing for frataxin.  Affected patients usually have 2 affected alleles, carriers have one.  Rarely, sequencing of second allele for FXN is needed to find a point mutation (compound heterozygosity).