Myopathy, Distal, Welander Type

Genetic disorder characterized by distal, late-onset myopathy. The presenting feature is in 89% of cases weakness and wasting of the small muscle of the hands. Myotonia and sensory changes are not present. Does not involve the heart.

Swedish Distal Myopathy type; Welander Muscular Atrophy.

Welander distal myopathy is observed almost exclusively in Sweden, where it was first described; more than 250 cases have been described.

Autosomal dominant inheritance. The gene causing Welander myopathy has not yet been identified but is restricted to a region of 2.4 cM on chromosome 2 (2p13).

Unknown, but the gene locus region overlaps with those of Miyoshi myopathy and limb-girdle muscular dystrophy IIB, both of which result from mutation in the dysferlin gene.

Levels of creatine kinase are normal to slightly increased. The most prominent finding on light microscopy is that of rimmed vacuoles and tubulofilamentous inclusions evidenced by ultrastructural examination.

Distal myopathy with late onset (after age 40 years). The first symptom is clumsiness in performing fine motor skills with the index finger and thumb. The weakness subsequently progresses to all the finger extensor muscles, and atrophy of intrinsic hand muscles becomes manifest after several years' duration. The weakness later extends to the anterior muscles of the legs with inability to raise the forefoot appropriately. No proximal weakness and no cardiomyopathy. Progression is slow and does not affect life expectancy.

No literature about this condition and anesthesia, but certain considerations must be made. Obtain complete workup, including neurologic and motor milestones, family history, and previous problems. Cardiac function should be assessed in light of cardiomyopathic potential of other distal myopathy. ECG, echocardiography, and/or cardiac catheterization may be appropriate. Other syndromic features should be sought.

Cardiomyopathic cases (Welander/ Swedish type) in general have greater implications for anesthesia. Patients manifesting cardiomyopathy require cardiac monitoring depending on the degree of disease.

Use extreme caution with thiopentone and muscle relaxants; avoid respiratory depressant drugs.

Distal Myopathy Type I (MPD I): Late distal myopathy with small hand muscle weakness and wasting. Also associated with a very slow progressive cardiomyopathy. It is inherited as an autosomal dominant pattern.

Miyoshi Myopathy (Late-Onset Distal Muscular Dystrophy): Characterized by onset between 16 and 20 years in 80% of cases, with muscular involvement of lower legs and forearms; small muscles of the feet and hands are relatively spared.

Inclusion Body Myopathy: Characterized by muscular dystrophy, especially of the anterior tibial muscles. Although the hamstring and tibialis anterior muscles are affected severely by early adulthood, the quadriceps muscles are spared even in a late stage of the disorder.

Limb-Girdle Muscular Dystropy (LGMD): Genetically heterogeneous group of inherited progressive muscular disorders that affect mainly the proximal musculature (hip and shoulder). Several different types have been identified; at least eight have autosomal recessive inheritance and three others are transmitted as an autosomal dominant trait. In most individuals, associated symptoms and findings become apparent during childhood; however, the disease may also present itself during adolescence or adulthood. The muscle weakness may spread from the lower limbs to the upper limbs or vice versa. Although the disorder typically progresses slowly, some affected individuals experience rapid disease progression.