Congenital muscular dystrophy with adducted thumbs, ptosis, external ophthalmoplegia, mental retardation and cerebellar hypoplasia: a novel form of CMD

Abstract

At least six different forms of congenital muscular dystrophy are associated with structural changes of the central nervous system, and three of these have been mapped: merosin-deficient congenital muscular dystrophy on chromosome 6q2, Fukuyama congenital muscular dystrophy on chromosome 9q31, and muscle eye brain disease on chromosome 1p32. Walker-Warburg syndrome, congenital muscular dystrophy with calf hypertrophy, pontocerebellar hypoplasia, and normal eyes, and congenital muscular dystrophy with severe mental retardation and cerebellar cysts are nosologically distinct and have been excluded from the known congenital muscular dystrophy loci with structural changes of the central nervous system. Here, we describe a novel congenital muscular dystrophy syndrome which is phenotypically distinct from the recognized forms of congenital muscular dystrophy with brain involvement. Two siblings, a boy and a girl, were born to consanguineous parents from Sicily. Both children were born with adducted thumbs and toe contractures. They were floppy from birth, walked late, showed profound generalized muscle weakness including facial muscles, elevated creatine kinase levels of 200–700 U/l, and histological changes compatible with muscular dystrophy. In addition, both showed ptosis, external ophthalmoplegia, mild mental retardation, and mild cerebellar hypoplasia on MRI. Immunocytochemistry showed normal expression of muscle membrane proteins including laminin α 2, laminin β 2, and α-dystroglycan. Linkage analysis excluded the candidate loci on chromosomes 6q2, 9q31, and 1q32. The gene locus for congenital muscular dystrophy 1B, MDC 1B, on chromosome 1q42 was also excluded. Adducted thumbs are a distinct clinical sign that has not been reported in congenital muscular dystrophy before and should facilitate recognition of further patients with this disorder.