Juvenile-onset permanent weakness in muscle phosphofructokinase deficiency.

We describe a 41-year-old Moroccan woman with phosphofructokinase (PFK) deficiency who presented slowly progressive muscular weakness since childhood, without rhabdomyolysis episode or hemolytic anemia. Deltoid biopsy revealed massive glycogen storage in the majority of muscle fibers and polysaccharide deposits. PFK activity in muscle was totally absent. A novel homozygous non-sense mutation was detected in PFKM gene. Our observation suggests that juvenile-onset fixed muscle weakness may be a predominant clinical feature of PFK deficiency. Vacuolar myopathy with polyglucosan deposits remains an important morphological hallmark of this rare muscle glycogenosis.