A heterogeneous group of muscle disorders of genetic origin. They are characterized by starting with a isolated weakness of the distal muscles of the lower and/or upper limbs (more rarely). They are caused by mutations of genes other mutations of which cause more severe myopathies and/or cardiomyopathies. Their diagnosis therefore involves  an ECG, an echocardiography, an EMG of the affected muscles, a muscle MRI (muscle tissue is replaced by fat) and sometimes the biopsy of a affected muscle (typical image of rimmed vacuoles and sometimes anomaly of the fiber sizes and  of the distribution of their nuclei). CPK's levels are generally high (2 to 3 x normal values).

Two groups are identified according to their mode of transmission;

• autosomal dominant transmission:

1)        Welander muscular dystrophy [MIM 604 454]. Especially in Sweden and Finland. Mutation of the TIA gene (2p13.3). Onset usually after 40 years of age. The extensors of the fingers and wrist are affected first. The intrinsic muscles of the  hand are affected later as well as the flexors of the feet.

2)  Udd/Markesbery-Griggs muscular dystrophy (Tibial muscular dystrophy) [MIM 600 334]: in Finland: 2/10,000. Mutation of the TTN gene (2q31.2) coding for titin. It occurs in adults after 35 years of age, usually between 45 and 55. The evolution is slow and not very disabling. Muscle involvement is usually limited to the legs (anterior hamstrings) and is sometimes asymmetrical. The loss of walking remains exceptional, even if the use of a cane may sometimes be necessary. Later, a lack of strength of some muscles of the wrist and hand may appear. Biopsy: presence of central nuclei and rimmed vacuoles.
In the case of a homozygous form, the disease manifests itself more severely and earlier (in childhood or adolescence), and presents a phenotype of girdle dystrophy (see this term and LGMG2J)

3)        early-onset distal myopathy of the Laing type: see this term

4)        Tateyama muscular dystrophy [MIM 614 321]: incidence < 1.106. Mutation of the CAV3 gene (3p25.3) coding for caveolin. Progressive onset of muscle atrophy with limited loss of strength in the muscles of the hands and feet. Presence of rippling in response to muscle percussion. CPK's levels are high. 
Biopsy: predominance of fibers I, dystrophic lesions and absence of caveolin 3 in the affected muscles

5)        distal myopathy with weakness of the vocal cords [MIM 606 070]. Very rare. Mutation of the MATR3 gene (5q31) coding for matrine  3.  Involvement of the extensors of the toes, anterior tibial muscles or fingers. Hypophonia and swallowing problems are common. Close to amyotrophic lateral sclerosis type 21 (see this term).

• autosomal recessive transmission:

1)        Nonaka distal myopathy: see  this term

2)        Miyoshi-type distal myopathy More common in  Libyan and Israeli Jews, and Italian and Spanish populations. The most common form (type 1) [MIM 254 130] is due to a mutation of the DYSF gene (2p13) coding for dysferlin. Type 2 [MIM 613 318] is caused by a mutation of a gene in 8q22.3, and type 3 [MIM 613 319] by a mutation of the ANO5 gene (11p14). Usually symmetrical atrophy of the calf muscles (soleus and gastrocnemius). Stress myalgia.  It is characterized by a massive elevation  of CPK levels and dystrophic-like muscle lesions while most other distal myopathies are characterized histologically by the presence of lined vacuoles

3)        oculo-pharyngodistal myopathy: see this term

Anesthetic implications:

check for heart involvement;  It is probably  prudent to avoid succinylcholine and halogenated agents given the risk (although probably small) of rhabdomyolysis.

References:

-        Stojkovic T, Richard P, Béhin A.
Myopathies distales.
EMC 2014; 17-175-D-10

Updated: January 2023