Multi-minicore disease (MmD) is an infrequent congenital
myopathy, defined by structural changes in optic and electron microscopy, namely, multiple small areas lacking oxidative
enzyme activity and focal disorganization of
contractile proteins involving at most a few sarcomeres. The classical form of the disease manifests as more or less severe
hypotonia and generalized weakness with predominance in axial and proximal limb muscles. Clinical variants also exist. Usually MmD is inherited as an autosomal recessive trait. Genetic heterogeneity is recognized and up to now mutations in the genes of
RYR1 and SEPN1 have been detected. We record three unrelated cases of MmD. Case 1, with the classical benign form, was followed-up for 15 years. Case 2, presenting pharyngolaryngeal involvement and severe delay of head control, improved gradually, until independent gait was acquired at age of six years. A moderate restriction of daily life activities remains. Case 3, of antenatal-onset, was expressed by
arthrogryposis of hands, predominance of scapular girdle deficit and a stable course after ten years on physiotherapy. All cases were selected by the characteristic morphological abnormalities in biceps brachii samples, including electron microscopy. Emphasis is given to case 2 due to type 1 fiber uniformity and mild endomysial
fibrosis, posing a difficult differential diagnosis with congenital
muscular dystrophy were it not for the significant number of multi-minicores.