Novel and recurrent mutations in lamin A/C in patients with Emery-Dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy (EDMD) is characterized by slowly progressive muscle wasting and weakness; early contractures of the elbows, Achilles tendons, and spine; and cardiomyopathy associated with cardiac conduction defects. Clinically indistinguishable X-linked and autosomal forms of EDMD have been described. Mutations in the STA gene, encoding the nuclear envelope protein emerin, are responsible for X-linked EDMD, while mutations in the LMNA gene encoding lamins A and C by alternative splicing have been found in patients with autosomal dominant, autosomal recessive, and sporadic forms of EDMD. We report mutations in LMNA found in four familial and seven sporadic cases of EDMD, including seven novel mutations. Nine missense mutations and two small in-frame deletions were detected distributed throughout the gene. Most mutations (7/11) were detected within the LMNA exons encoding the central rod domain common to both lamins A/C. All of these missense mutations alter residues in the lamin A/C proteins conserved throughout evolution, implying an essential structural and/or functional role of these residues. One severely affected patient possesed two mutations, one specific to lamin A that may modify the phenotype of this patient. Mutations in LMNA were frequently identified among patients with sporadic and familial forms of EDMD. Further studies are needed to identify the factors modifying disease phenotype among patients harboring mutations within lamin A/C and to determine the effect of various mutations on lamin A/C structure and function.

Prenatal diagnosis of fatal infantile olivopontocerebellar hypoplasia syndrome

We report the first case of prenatal diagnosis of fatal infantile olivopontocerebellar hypoplasia syndrome, OMIM 225753. Ultrasound findings noted at 28 weeks' gestation included polyhydramnios, a small stomach bubble, a small but morphologically normal cerebellum, dilatation of the fourth ventricle, and long periods of normal fetal movement punctuated by sudden bursts of violent seizure-like activity of the fetal extremities. At birth, the child was noted to be hypertonic, myoclonic, hyper-reflexic, demonstrated poor gastrointestinal motility, and had severe apneic episodes. Magnetic resonance imaging (MRI) demonstrated marked hypoplasia or atrophy of the cerebellum, pons and medulla, mild atrophy of the cerebral cortex, and mild ex vacuo venticulomegaly of the fourth, third and lateral ventricles. This child died from respiratory insufficiency at 14 days of age. The parents of this child had previously lost a child with similar clinical and anatomical findings. Prenatal sonographers should be aware of the existence of this rare syndrome and should look carefully at the size of the cerebellum in cases of polyhydramnios or when in utero 'seizure-like' activity is seen. The importance of establishing this diagnosis lies in the fact that it appears to have a very poor postnatal prognosis and is likely to be inherited as an autosomal recessive disease.