Minicore Diseas..

Congenital myopathy associated with proximal extremity weaknesses, external ophthalmoplegia, and eventual respiratory failure. In the neonatal subgroup, severe hypotonia, delayed motor development, generalized muscle weakness and amyotrophy which may progress or remain stable. This presentation corresponds to a subgroup called “Central core disease" and susceptibility to malignant hyperthermia has been suggested.

MmD; Multicore Myopathy with External Ophthalmoplegia; Minicore Myopathy with External Ophthalmoplegia.

Remains unknown. No more than 30 cases of this medical condition have been reported in the literature.

Autosomal recessive; also a possible dominant form.

Myopathy characterized by the presence of multiple, short, core lesions (known as minicores) in most muscle fibers as a result of sarcomere disorganization and mitochondria depletion. Four subgroups have been identified. RYR1 mutations were recently identified in the moderate form—the central core disease. The genes responsible for the three other forms remain unknown, but a mutation of the selenoprotein N gene is implicated.

The most prevalent phenotype is characterized by the predominance of axial muscle weakness that leads, in two thirds of patients, to development of severe life-threatening respiratory insufficiency and scoliosis. The second group is the classic form with ophthalmoplegia, which occurs in only 10% of cases. The third group consists of the mild cases of central core disease. The fourth group is rare and probably consists of rigid spine dystrophy.

Assessment of severity of respiratory failure and degree of cardiac involvement is necessary, with complete pulmonary function test, blood gas analysis, and echocardiography.

High complication rate because of muscle weakness, respiratory insufficiency, and cardiac myopathy (late onset). A risk for malignant hyperthermia has been suggested in the subgroup (e.g., central core disease) of the disease but remains unknown in the classic form. Positioning may be challenging because of often severe spinal deformity.

Succinylcholine should be considered absolutely contraindicated. Muscle relaxants are usually not mandatory and must be carefully adjusted if used. Volatile halogenated agents are not advisable because of the possibility of malignant hyperthermia.

Central core disease of muscle, rigid spine muscular dystrophy. Association with short-chain acyl-CoA dehydrogenase deficiency has been described.

Docquer MA, Veyckemans F, Prudhomme S, et al: Anesthesia in a child presenting a anhydrotic ectodermic dysplasia associated with a multiminicore myopathy. Can J Anaesth 47:449, 2000.
Ferreiro A, Quijano-Roy S, Pichereau C, et al: Mutations of the selenoprotein N gene, which is implicated in rigid spine dystrophy, cause the classical phenotype of multiminicore disease: Reassessing the nosology of early-onset myopathies. Am J Hum Genet 71:739, 2002.  [PubMed: 12192640]
Jungbluth H, Sewry C, Brown SC, et al: Minicore myopathy in children: A clinical and histopathological study in 19 cases. Neuromuscul Disord 10:264, 2000.  [PubMed: 10838253]

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