We report three patients with a predominantly proximal myopathy due to p.A193T mutation in the actin-binding domain of FLNC, which has so far only been associated with a distal myopathy.
All patients in our neuromuscular unit with genetically unclassified, recessive limb girdle muscular dystrophy (LGMD2), Miyoshi-type distal myopathy (MMD) or persistent asymptomatic hyperCK-emia (PACK) were assessed for mutations in the ANO5 gene.
Mutations in dysferlin and anoctamin 5 are the cause of muscular disorders, with the main presentations as limb-girdle muscular dystrophy or Miyoshi type of distal myopathy.
Recessive mutations in the ANO5 gene have been recently identified in Northern Europe as a cause of non dysferlin-linked distal myopathy and limb girdle muscular dystrophy.
DNA samples of 101 patients in 95 kindreds at our quaternary referral center in Finland, who had undetermined limb-girdle muscular dystrophy (LGMD), calf distal myopathy, or creatine kinase (CK) elevations of more than 2,000 IU/L, were selected for ANO5 genetic evaluation, and the clinical findings of patients with mutations were retrospectively analyzed.
We conclude that the pattern of muscle involvement seen in patients with distal myopathy with anoctamin 5 mutations (MMD3) is typical and can thus be useful during the differential diagnosis process allowing for a more targeted molecular approach.
Recessive mutations in ANO5 cause primary skeletal muscle disorders (limb-girdle muscular dystrophy 2L and distal muscular dystrophy), which are phenotypically similar to dysferlinopathy, a muscular dystrophy due to dysferlin-encoding gene (DYSF) mutations.
Recessive mutations in anoctamin-5 (ANO5) are causative for limb-girdle muscular dystrophy (LGMD) 2 L and non-dysferlin Miyoshi-like distal myopathy (MMD3).
Mutations in CAV3 lead to various neuromuscular phenotypes with partial overlap, including limb girdle muscular dystrophy type 1C (LGMD1C), rippling muscle disease, distal myopathy and isolated hyperCKemia.
Mutations in the human caveolin-3 gene (cav-3) on chromosome 3p25 have been described in limb girdle muscular dystrophy, rippling muscle disease, hyperCKemia, and distal myopathy.
This case emphasizes that an R27Q missense mutation in the CAV3 gene can lead to various clinical phenotypes including hyperCKemia, rippling muscle disease, distal myopathy, and LGMD1C.
Mutations in the gene encoding caveolin-3 (CAV3) underlie four distinct disorders of skeletal muscle: the autosomal dominant form of limb-girdle muscular dystrophy type 1C (LGMD-1C), rippling muscle disease (RMD), sporadic and familial forms of hyperCKemia, and distal myopathy.
This study suggested that the CAV3 c.136G > A (p.Ala46Thr) mutation can cause MD as well as different phenotypes in different individuals, suggesting that additional unknown loci must affect the disease phenotypes.
Caveolin-3 mutations can result in four distinct, sometimes overlapping, muscle disease phenotypes: limb girdle muscular dystrophy, rippling muscle disease, distal myopathy, and hyperCKemia.
The desmuslin protein interacts with and is closely related to desmin, a protein encoded by a locus mutated in some forms of hereditary distal myopathy.
A missense mutation in the desmin rod domain is associated with autosomal dominant distal myopathy, and exerts a dominant negative effect on filament formation.