Hereditary inlcusion body myopathy type 2 (IBM2) is characterized by adult-onset, slowly progressive distal muscle weakness that begins with gait disturbance and foot drop secondary to anterior tibialis muscle weakness. Affected individuals are usually wheelchair-bound about 20 years after onset. If quadriceps sparing is incomplete, loss of ambulation tends to occur earlier.
The gene GNE encodes the bifunctional enzyme UDP-N-acetylglucosamine 2-epimerase/ N-acetylmannosamine kinase. IBM2 is inherited in an autosomal recessive manner. It is most common in people from Middle Eastern Jewish background - about one in 15 Persian Jews is a carrier.