Minicore myopathy in children: a clinical and histopathological study of 19 cases

Minicore myopathy is a congenital myopathy characterized by multifocal area s of degeneration in muscle fibres. Genetic heterogeneity expected on the b asis of clinical variability awaits further resolution. We reviewed 19 case s in order to further delineate the phenotype. Marked hypotonia was the pre dominant presenting feature, with evidence of antenatal onset in 30% of cas es. Weakness was most pronounced axially and proximally, often more severel y affecting the shoulder girdle. Mild facial involvement was frequent. Vary ing degrees of scoliosis were obvious in all patients older than 10 years. In addition, two patients who were also the most severely affected had comp lete external ophthalmoplegia. One patient showed marked distill involvemen t. Respiratory failure developed in half of all patients after 10 years of age and correlated strongly with the degree of scoliosis. Cardiac involveme nt occurred mainly secondary to respiratory impairment. The course appeared static in most cases. toss of independent walking was observed only in one case at the age of 10 years. On ultrasound scan, differential involvement within the quadriceps was documented in several patients. Variability in fi bre size, type 1 predominance and atrophy with occasional type 2 hypertroph y were prominent but nonspecific histological changes. Apart from typical m inicores, a marked increase in internal nuclei was the most prominent histo logical feature. With the exception of one family in which two generations were affected. inheritance appeared autosomal-recessive or sporadic in all cases. (C) 2000 Elsevier Science B.V. All rights reserved.