Francesco Martinello

Laminin α2 muscular dystrophy: Genotype/phenotype studies of 22 patients

Objective: To determine the number of primary laminin α2 gene mutations and to conduct genotype/phenotype correlation in a cohort of lamininα2-deficient congenital muscular dystrophy patients. Background: Congenital muscular dystrophies (CMD) are a heterogenous group of muscle disorders characterized by early onset muscular dystrophy and a variable involvement of the CNS. Laminin α2 deficiency has been reported in about 40 to 50% of cases of the occidental, classic type of CMD.1,2 Laminin α2 is a muscle specific isoform of laminin localized to the basal lamina of muscle fibers, where it is thought to interact with myofiber membrane receptor, such as integrins, and possibly dystrophin-associated glycoproteins.3,4 Methods: Seventy-five CMD patients were tested for laminin α2 expression by immunofluorescence and immunoblot. The entire 10 kb laminin α2 coding sequence of 22 completely laminin α2-deficient patients was screened for causative mutations by reverse transcription (RT)-PCR/single strand conformational polymorphisms (SSCP) analysis and protein truncation test(PTT) analysis followed by automatic sequencing of patient cDNA. Clinical data from the laminin α2-deficient patients were collected. Results: Thirty laminin α2-negative patients were identified (40% of CMD patients tested) and 22 of them were screened for laminin α2 mutations. Clinical features of laminin α2-deficient patients were similar, with severe floppiness at birth, delay in achievement of motor milestones, and MRI findings of white matter changes with normal intelligence. Loss-of-function mutations were identified in 95% (21/22) of the patients studied. SSCP analysis detected laminin α2 gene mutations in about 50% of the mutant chromosomes; PTT successfully identified 75% of the mutations. A two base pair deletion mutation at position 2,096-2,097 bp was present in 23% of the patients analyzed. Conclusions: Our data suggest that the large majority of laminin α2-deficient patients show laminin α2 gene mutations.

Genetic epidemiology of congenital muscular dystrophy in a sample from north-east Italy

Congenital muscular dystrophy (CMD) is a heterogenous disease with autosomic recessive transmission. In an epidemiological study in four provinces of Veneto (region of 2586830 inhabitants in north-east Italy), the recorded incidence rate for the period 1979–1993 was 4.65 x 10−5; the prevalence rate in the year 1993 was 6.8 × 10−6. The incidence and the prevalence rates that we have obtained during the course of our investigation represent the first estimates for CMD in Europe and show that this myopathy is among the most frequent neuromuscular diseases with autosomic recessive transmission.

Supplemental therapy in isolated vitamin E deficiency improves the peripheral neuropathy and prevents the progression of ataxia

A 24-year-old male, who suffered since childhood from a progressive form of ataxia associated with peripheral neuropathy, was found severely deficient in serum vitamin E. He walked with bilateral aid and presented severe dysmetria of the limbs and dysarthric speech; muscular strength and trophism were slightly diminished in the distal muscles of four limbs and there was hypotonia of the arms; he presented absent deep tendon reflexes, bilateral Babinskis sign, reduced proprioception at four limbs, pes cavus and fasciculations of the tongue. Intestinal fat malabsorption and other gastrointestinal or haematological conditions associated with deficiency of this vitamin were ruled out. In this patient, after 2 years of a daily supplement of high doses of vitamin E, a further progression of the disease was not observed and, moreover, the neurophysiological characteristics of his neuropathy appeared clearly improved. A longitudinal evaluation of serum vitamin E levels showed values in the normal range after 13 months of therapy. The patient had molecular genetic analysis of chromosome 8 and was found homozygous for the unusual mutation 513insTT in the alpha-tocopherol transfer protein gene.

Clinical and neuroimaging study of central nervous system in congenital myotonic dystrophy.

Abstract We present the clinical and neuroimaging findings of five patients (four males, one female; mean age 12 years) affected by congenital myotonic dystrophy and the correlation with their molecular genetic analysis. At birth all five presented severe muscular weakness and hypotonia, associated with feeding difficulties and respiratory distress. In the same patients, congenital clubfoot or more generalized arthrogryposis was also evident. Lymphocyte DNA was characterized in each by a CTG repeat longer than 1300 in the region of the myotonic dystrophy gene in chromosome 19. The patients’ neurological condition was evaluated by clinical examination, intelligence tests, electroencephalography, and brain magnetic resonance imaging. All five suffered from some impairment of intellectual function (IQ ranged from 52 to 79). In three a longitudinal evaluation of the cognitive deficit detected no deterioration. In all patients magnetic resonance imaging showed some degree of ventricular dilatation, loosely correlated to the cognitive impairment; in three there was hypoplasia of the corpus callosum and in two mild abnormalities of supratentorial white matter. The relationship between the size of the CTG repeat expansion found in lymphocyte DNA and the cerebral abnormalities appeared inconsistent in this unusual myoencephalopathy of the newborn.

Divergence of Central Nervous System Involvement in 2 Italian Sisters with Congenital Muscular Dystrophy: A Clinical and Neuroradiological Follow-Up

We report the clinical and neuroradiological follow-up of 2 Italian sisters, 10 and 6 years of age, affected by congenital muscular dystrophy (CMD) with divergent CNS involvement. In both, CMD was diagnosed by finding dystrophic alterations in muscle biopsy and muscular deficit at birth. The elder sister suffered also from marked intellectual deficit and epilepsy, as usually reported in children with Fukuyama CMD. In the same patient, at 2 years of age, CT scan showed severe hypodensity of cerebral white matter and severe ventricular dilatation of occipital horns. At 8 years of age, MRI also showed clearcut pachygyria mainly in the parietal and occipital lobes. MRI and CT scan at the same age showed improvement of the leukoencephalopathy and unchanged ventricular dilatation, as reported for patients with Fukuyama CMD. Unlike Japanese cases, however, she showed no progression in her muscular deficit and her muscle immunostaining of laminin M chain (merosin) was normal. The younger sister had normal mental development, never experienced epileptic fits and had always normal EEG. However, as often seen in classical CMD, her CT scan showed moderate hypomyelination of cerebral white matter and mild dilatation of lateral ventricles. MRI did not show any other brain abnormalities. Sequential CT scan at 2, 4 and 6 years of age showed improvement of the leukoencephalopathy. Her muscular deficit had a stationary clinical course. Her immunostaining of muscle merosin was moderately reduced. The finding of Fukuyama-like and classical CMD in 2 sisters indicates the possibility that different forms of CMD may be different expressions of the same genetic disease.

Brain alterations in the classical form of congenital muscular dystrophy

In the classical form of congenital muscular dystrophy (CMD), subclinical brain involvement is frequent. In order to establish the natural evolution of CNS alterations in this type of CMD, the cerebral functions of 12 cases were examined longitudinally for a mean period of 8 years. There were 7 boys and 5 girls, with a mean age of 5 years at first evaluation and 13 at the last one. Merosin expression in muscle fiber basement membrane, evaluated in 10 of them, was normal in 6 and deficient in 4. CNS conditions were followed up by repeated neuropsychiatric examinations, intelligence tests, EEG and brain CT scan and/or MRI. Eight of the 12 patients (including the 4 with merosin-deficiency) had normal intelligence, while 4 had mild to moderate mental retardation: in all the intellectual ability was unchanged during the follow-up study. CT scan detected minor brain alterations in 9 patients: 6 of these, the 4 with merosin deficiency and 2 others in whom merosin was not evaluated, presented leukoencephalopathy: on neuroimaging reappraisal it was unchanged in 3, improved in 2 and worse in 1 (a merosin-deficient case). Cerebellar alterations or mild ventricular dilatation were detected in 8 cases, including 3 merosin-non-deficient ones: these abnormalities were unchanged at the last study by CT and MRI, as were the normal neuroimaging findings observed in 3 other cases. Overall, during our study the brain alterations found in classical CMD showed a stationary or an improving course; progressive worsening was observed only in 1 of 4 merosin-deficient cases with leukoencephalopathy.

Congenital muscular dystrophy with partial merosin deficiency and late onset epilepsy.

Merosin, the laminin α2 chain located on the surface of muscle fibers, has recently been shown to be absent in a subset of cases with the classical type of congenital muscular dystrophy (Cl-CMD). By immunocytochemistry and immunoblot analysis, using monoclonal antibodies to both the 80- and the 320-kDa fragments, the same protein was found to be only partially deficient in 3 of our cases. All these 3 patients were able to walk, with evidence of a mild to moderate muscle involvement, as opposed to the merosin-negative cases which are never ambulant because they are affected by severe muscular deficit. All of them also suffered from a late onset form of epilepsy, a clinical expression of brain involvement rarely described in cases with merosin-negative CMD. The 3 patients with CMD and partial merosin deficiency were investigated by brain MRI and pattern reversal visual evoked potentials (VEP) associated with electroretinography (ERG). The results were compared with those obtained by similar studies on 3 of our cases with complete merosin deficiency. In both types of patients, the neuroimaging evaluation showed supratentorial white matter changes, usually of moderate degree, irrespective of the amount of merosin detected in muscle. The VEP were normal in all the 3 cases with partial merosin deficiency, whereas they showed reduced amplitude or prolonged latency in all the 3 cases with the merosin-negative form. ERG was normal in all 6 cases. As a whole, our data indicate that leukoencephalopathy does not seem to distinguish between the two variants of Cl-CMD. On the other hand, a benign muscle involvement and normal VEP findings seem to distinguish CMD patients with partial merosin deficiency from those with complete deficiency of the same protein. Late onset epilepsy, evident in all our 3 cases with partial merosin deficiency, needs to be evaluated in a larger series of patients in order to be considered a characteristic of this variant of CMD.