The first Italian family with tibial muscular dystrophy caused by a novel titin mutation

Tibial muscular dystrophy (TMD) or Udd myopathy is an autosomal dominant distal myopathy with late onset, at first described in the Finnish population. We report here the first Italian cases of TTN mutated titinopathy. The proband, a 60 year-old female, had the first muscular signs at the age of 59 years, with difficulty in walking and right foot drop. Muscle imaging showed selective fatty degenerative change in the anterior compartment of leg muscles. Her 67 year-old brother, started to show muscle weakness, pain at lower limbs and hypertrophy of calf muscles at the age of 66 years. Their mother began to show foot drop and impaired walking from the age of 60 years. Other relatives are reported to be affected in a similar way. Because the phenotype appeared compatible with TMD, we analyzed the TTN gene in the DNA of the proband and we identified a heterozygous mutation 293326A>C. This mutation is also present in the brother and in the other affected individuals of the same family. The mutation predicts a His33378Pro change located next to the previously known Belgian TMD mutation. The mutation was not found in 100 Italian control DNA samples. Then, since the introduction of a proline in the last domain of titin was previously known to cause TMD in French families, we can conclude that this missense mutation is the obvious pathogenetic mutation in the affected patients. No other disease causing mutations in the TTN gene have so far been reported in the Italian population.