Inherited symmetric muscular weakness, initially of
the lower limbs, with slow progression and associated cardiac anomalies.
This term includes: Limb-Girdle Muscular Dystrophy; Leyden-Möbius
Muscular Dystrophy; Pelvofemoral Muscular Dystrophy; Scapulohumeral Muscular
The earliest description of the proximal muscular
dystrophy is described to Leyden and Möbius in 1876 and 1879, respectively.
They described adult patients with pelvic and femoral distribution of
weakness and atrophy with a benign course. At that time, the differentiation
between the spinal muscular atrophies and weakness associated with central nervous system (CNS)
disorders and primary muscle disease had not been established.
Exact figures are not available. The frequency in the
general population because of the heterogenous nature of this disease. There
is no racial predilection and it affects either sex equally.
The mutation for this disease is located on
the long arm of chromosome 1 and inheritance is most often autosomal
dominant, although an autosomal recessive variant may exist as well. Recent
genetic research demonstrated that Emery-Dreifuss and proximal muscular
dystrophy are allelic disorders.
The pathophysiology of the proximal muscular dystrophies
depends on the specific genetic defect of each associated condition and is discussed with
each individually in this book.
Of the various muscular dystrophies, the dystrophinopathies are
the most common, accounting for the majority of male disease and 10% of female patients
presenting for muscular dystrophy or persistent high serum creatine kinase.
Symmetric muscular weakness starts proximal in
the lower extremities usually before the age of 20 years. Slow progression
over the next 10 to 20 years results also in weakness of the upper limb. In
contrast to Bethlem myopathy and Emery-Dreifuss muscular dystrophy,
contractures of the elbows and the Achilles tendon are absent or subtle.
Cardiologic abnormalities (atrioventricular conduction defects with
arrhythmias and risk of sudden death) occur in almost two-thirds of these
patients. Rarely, dilated cardiomyopathy may be present. In general,
neuromuscular symptoms precede cardiac abnormalities. Serum creatine
phosphokinase levels are either normal or only moderately elevated.
Cardiac evaluation with ECG and
echocardiography is recommended. If the patient already has a pacemaker,
ensure proper function. Although congenital myopathies have been associated
with malignant hyperthermia, the evidence supporting this causal
relationship is poor. No case reports of malignant hyperthermia reaction in
proximal muscular dystrophy have been published. Nevertheless, caution
should be exercised when using known trigger agents and full monitoring
(including core and peripheral temperature) should be used in the
Avoidance of known trigger agents may
be advisable until more information about the condition is available. If
nondepolarizing muscle relaxants are to be used, they should be titrated to
effect by using a peripheral nerve stimulator. Cis-atracurium can be used and seems to offer good
neuromuscular blockade without prolongation of recovery. However, a delayed onset of action is possible.
The benign myopathy
associated with this condition, which makes it unique amongst the other