Severe progressive form of congenital muscular dystrophy with calf pseudohypertrophy, macroglossia and respiratory insufficiency

Elevated serum creatine kinase and small cerebellum prompt diagnosis of congenital muscular dystrophy due to FKRP mutations

Fukutin-related protein (FKRP) is a putative glycosyltransferase that mediate O-linked glycosylation of the α-dystroglycan. Mutations in the FKRP gene cause a spectrum of diseases ranging from a limb girdle muscular dystrophy 2I (LGMD2I), to severe Walker-Warburg or muscle-eye-brain forms and a congenital muscular dystrophy (with or without mental retardation) termed MDC1C. This article reports on a Moroccan infant who presented at birth with moderate floppiness, high serum creatine kinase (CK) levels, and brain ultrasonograph suggestive of widening of the posterior fossa. Muscle biopsy displayed moderate dystrophic pattern with complete absence of α-distroglycan and genetic studies identified a homozygous missense variant in FKRP. Mutations in FKRP should be looked for in forms of neonatal-onset hyperCKaemia with floppiness and small cerebellum.

Sleep-disordered breathing in children with congenital muscular dystrophies

OBJECTIVE

Most types of neuromuscular diseases are known to be associated with a high risk of sleep-disordered breathing. We performed a prospective study in a well individualized group of muscular disorders, congenital muscular dystrophies (CMD), to characterize the frequency of sleep-disordered breathing and thereby to determine the potential usefulness of sleep studies in such patients.

METHODS

Twenty CMD children (12 F, 8 M, aged 4-17 years) were included. Using overnight polysomnography, we determined the following parameters: sleep stages, sleep latency, sleep efficiency index, wake time duration, total sleep time (TST), apnea/hypopnea index (AHI), arterial blood oxygen saturation, and nocturnal paroxysmal EEG activity.

RESULTS

As compared to healthy controls, we detected in our study group frequent awakenings, a decreased TST (mean 448 ± 44.4 min) and a decreased REM duration (mean 11.5 ± 3.5% of TST). Significant increase in wake time duration (28-90 min) and decrease in REM duration were observed in 12 patients. An apnea/hypopnea syndrome was detected in 13 patients (65%) with central apneas in 8, obstructive apneas in 2 and 3 mixed apneas in 3 patients. AHI was >10 in 3 cases, <10> 5 in 4 cases and were concomitant with blood oxygen de-saturation in four cases. NPA were detected in 10 patients ranging from 10 to 40% of TST.

INTERPRETATION

Our results confirm the high incidence of sleep disordered breathing in children with CMD, and thereby, the usefulness of overnight polysomnography recordings in such patients.

Congenital muscular dystrophies: a brief review

Congenital muscular dystrophies (CMDs) are clinically and genetically heterogeneous neuromuscular disorders with onset at birth or in infancy in which the muscle biopsy is compatible with a dystrophic myopathy. In the past 10 years, knowledge of neuromuscular disorders has dramatically increased, particularly with the exponential boost of disclosing the genetic background of CMDs. This review will highlight the clinical description of the most important forms of CMD, paying particular attention to the main keys for diagnostic approach. The diagnosis of CMDs requires the concurrence of expertise in multiple specialties (neurology, morphology, genetics, neuroradiology) available in a few centers worldwide that have achieved sufficient experience with the different CMD subtypes. Currently, molecular diagnosis is of paramount importance not only for phenotype-genotype correlations, genetic and prenatal counseling, and prognosis and aspects of management, but also concerning the imminent availability of clinical trials and treatments.

Consensus statement on standard of care for congenital muscular dystrophies

Congenital muscular dystrophies are a group of rare neuromuscular disorders with a wide spectrum of clinical phenotypes. Recent advances in understanding the molecular pathogenesis of congenital muscular dystrophy have enabled better diagnosis. However, medical care for patients with congenital muscular dystrophy remains very diverse. Advances in many areas of medical technology have not been adopted in clinical practice. The International Standard of Care Committee for Congenital Muscular Dystrophy was established to identify current care issues, review literature for evidence-based practice, and achieve consensus on care recommendations in 7 areas: diagnosis, neurology, pulmonology, orthopedics/rehabilitation, gastroenterology/ nutrition/speech/oral care, cardiology, and palliative care. To achieve consensus on the care recommendations, 2 separate online surveys were conducted to poll opinions from experts in the field and from congenital muscular dystrophy families. The final consensus was achieved in a 3-day workshop conducted in Brussels, Belgium, in November 2009. This consensus statement describes the care recommendations from this committee.

POMGnT1, POMT1, and POMT2 mutations in congenital muscular dystrophies

Alpha-dystroglycanopathies are a group of rare inherited neuromuscular disorders characterized by reduced glycosylation of alpha-dystroglycan (alpha-DG). Mutations in six genes (POMT1, POMT2, POMGNT1, FKTN, FKRP, and LARGE) have been identified in patients with alpha-dystroglycanopathies. Due to an extremely broad clinical spectrum and relatively poor phenotype-genotype correlation, diagnosis of alpha-dystroglycanopathies is difficult and requires searching for mutations gene by gene. At present, of the six proteins involved on alpha-dystroglycanopathies, the function of the gene products is only known for POMT1, POMT2, and POMGnT1, all responsible for the O-mannosylglycan biosynthesis. This chapter describes the assay protocols to diagnose patients with alpha-dystroglycanopathy by measuring glycosyltransferase activity.

Four Caucasian patients with mutations in the fukutin gene and variable clinical phenotype

Fukuyama congenital muscular dystrophy (FCMD) is frequent in Japan, due to a founder mutation of the fukutin gene (FKTN). Outside Japan, FKTN mutations have only been reported in a few patients with a wide spectrum of phenotypes from Walker-Warburg syndrome to limb-girdle muscular dystrophy (LGMD2M). We studied four new Caucasian patients from three unrelated families. All showed raised serum CK initially isolated in one case and muscular dystrophy. Immunohistochemical studies and haplotype analysis led us to search for mutations in FKTN. Two patients (two sisters) presented with congenital muscular dystrophy, mental retardation, and posterior fossa malformation including cysts, and brain atrophy at Brain MRI. The other two patients had normal intelligence and brain MRI. Sequencing of the FKTN gene identified three previously described mutations and two novel missense mutations. Outside Japan, fukutinopathies are associated with a large spectrum of phenotypes from isolated hyperCKaemia to severe CMD, showing a clear overlap with that of FKRP.

POMT2 intragenic deletions and splicing abnormalities causing congenital muscular dystrophy with mental retardation

BACKGROUND

Alpha-dystroglycanopathies are a group of congenital muscular dystrophies (CMDs) with autosomal recessive inheritance characterized by abnormal glycosylation of alpha-dystroglycan. Although six genetic causes have been identified (FKTN, POMGNT1, POMT1, POMT2, FKRP, and LARGE) many alpha-dystroglycanopathy patients remain without a genetic diagnosis after standard exon sequencing. To date POMT2 mutations have been identified in CMD cases with a wide range of clinical severities from Walker-Warburg syndrome to limb girdle muscular dystrophy without structural brain or ocular involvement.

METHODS

We analyzed POMT2 in six CMD patients, who had severe diffuse muscle weakness, generalized joint contractures, microcephaly, severe mental retardation and elevated CK levels. Eye involvement was absent or limited to myopia or strabismus. We sequenced the coding regions of POMT2 using genomic DNA and cDNA generated from blood lymphocytes or B lymphoblastoid cell lines. Quantitative PCR analysis of genomic DNA was used to identify and determine the breakpoints of large deletions.

RESULTS

We report five novel mutations in POMT2, four of which were outside of coding exons, two large genomic deletions and two intronic single base substitutions that induced aberrant mRNA splicing.

CONCLUSIONS

Large scale DNA rearrangements (such as large deletions) and cryptic splice mutations, that can be missed on standard sequencing of genomic DNA, may be relatively common in POMT2. Additional techniques, such as sequencing of cDNA are needed to identify all mutations. These results also confirm that POMT2 mutations are an important cause of the less severe alpha-dystroglycanopathy phenotypes.

De novo LMNA mutations cause a new form of congenital muscular dystrophy

OBJECTIVE

To describe a new entity of congenital muscular dystrophies caused by de novo LMNA mutations.

METHODS

Fifteen patients presenting with a myopathy of onset in the first year of life were subjected to neurological and genetic evaluation. Histopathological and immunohistochemical analyses were performed for all patients.

RESULTS

The 15 patients presented with muscle weakness in the first year of life, and all had de novo heterozygous LMNA mutations. Three of them had severe early-onset disease, no motor development, and the rest experienced development of a "dropped head" syndrome phenotype. Despite variable severity, there was a consistent clinical pattern. Patients typically presented with selective axial weakness and wasting of the cervicoaxial muscles. Limb involvement was predominantly proximal in upper extremities and distal in lower extremities. Talipes feet and a rigid spine with thoracic lordosis developed early. Proximal contractures appeared later, most often in lower limbs, sparing the elbows. Ten children required ventilatory support, three continuously through tracheotomy. Cardiac arrhythmias were observed in four of the oldest patients but were symptomatic only in one. Creatine kinase levels were mild to moderately increased. Muscle biopsies showed dystrophic changes in nine children and nonspecific myopathic changes in the remaining. Markedly atrophic fibers were common, most often type 1, and a few patients showed positive inflammatory markers.

INTERPRETATION

The LMNA mutations identified appear to correlate with a relatively severe phenotype. Our results further broaden the spectrum of laminopathies and define a new disease entity that we suggest is best classified as a congenital muscular dystrophy (LMNA-related congenital muscular dystrophy, or L-CMD).

Brain MRI abnormalities in muscular dystrophy due to FKRP mutations

INTRODUCTION

FKRP mutations cause a muscular dystrophy which may present in the neonatal period (MDC1C) or later in life (LGMD2I). Intelligence and brain imaging have been previously reported as being normal in FKRP-associated muscular dystrophy, except in rare cases presenting with mental retardation associated with structural brain abnormalities.

PATIENTS AND METHODS

We studied cerebral MRIs in twelve patients with FKRP-associated muscular dystrophy presenting in infancy or early childhood, at ages between 14 months and 43 years. Two patients had severe cognitive deficits, four had mild-moderate mental retardation and the rest were considered to have normal intelligence. All, but one were wheelchair-bound and 7 were mechanically ventilated.

RESULTS

Brain MRI was abnormal in 9 of 12 patients. Brain atrophy was seen in 8 patients. One child had isolated ventricular enlargement at 4 years. Cortical atrophy involved predominantly temporal and frontal lobes and was most important at later ages. In two cases with serial images this atrophy seemed progressive. Three patients, two with severe and one with moderate mental retardation, showed structural abnormalities of the posterior fossa with hypoplasia of the vermis and pons, and cerebellar hemispheric cysts. These abnormalities were stable with time. Two of these three patients also showed diffuse white matter abnormalities in early childhood, which regressed with time.

CONCLUSIONS

MRI abnormalities are common in patients with FKRP-associated muscular dystrophy presenting at birth or in early childhood. Progressive brain atrophy is the most frequent finding. Posterior fossa malformations and transient white matter changes may be seen in patients with associated mental retardation.

Congenital muscular dystrophy in Arab children

The congenital muscular dystrophies are autosomal recessive disorders with different clinical phenotypes, the spectrum of which varies between different ethnic communities. We report our findings in 21 Arab children with congenital muscular dystrophy. All 21 cases were of the pure type, with normal mental status, except 1 case with perinatal hypoxic-ischemic insult. Fourteen were laminin alpha2 (merosin) deficient, and six were laminin alpha2 positive; laminin alpha2 status was not determined in one patient. None of the laminin alpha2-deficient patients achieved independent ambulation, whereas three of the laminin alpha2-positive patients were able to walk. The elevated levels of serum creatine kinase did not differentiate the two groups and tended to decrease after the age of 5 years. Radiologic evaluation demonstrated an abnormal central white-matter signal in 11 of 13 laminin alpha2-deficient and in 1 of 5 laminin alpha2-positive patients; none had evidence of brain dysplasia. Nerve conduction velocities were normal in 5 of 5 laminin alpha2-positive patients, whereas in the laminin alpha2-deficient patients, it was slow in 9 of 11 for the motor nerves and normal in 8 of 9 for the sensory nerve. Two of the laminin alpha2-positive patients had pseudohypertrophy of the calves, and two of the laminin alpha2-deficient ones had seizures. The patient in whom the laminin alpha2 status was not determined had a severe course, an abnormal central white-matter signal, and epilepsy and resembled more the laminin alpha2-deficient group.

The congenital muscular dystrophies: recent advances and molecular insights

Over the past decade, molecular understanding of the congenital muscular dystrophies (CMDs) has greatly expanded. The diseases can be classified into 3 major groups based on the affected genes and the location of their expressed protein: abnormalities of extracellular matrix proteins (LAMA2, COL6A1, COL6A2, COL6A3), abnormalities of membrane receptors for the extracellular matrix (fukutin, POMGnT1, POMT1, POMT2, FKRP, LARGE, and ITGA7), and abnormal endoplasmic reticulum protein (SEPN1). The diseases begin in the perinatal period or shortly thereafter. A specific diagnosis can be challenging because the muscle pathology is usually not distinctive. Immunostaining of muscle using a battery of antibodies can help define a disorder that will need confirmation by gene testing. In muscle diseases with overlapping pathological features, such as CMD, careful attention to the clinical clues (e.g., family history, central nervous system features) can help guide the battery of immunostains necessary to target an unequivocal diagnosis.

EMG and nerve conduction studies in children with congenital muscular dystrophy

Motor and sensory nerve conduction velocities (NCVs) and needle electromyography (EMG) results were reviewed in 26 children with different types of congenital muscular dystrophy (CMD), including patients with mutations in the genes LAMA2, FKRP, and COL6A2. In every patient, at least one EMG examination detected myopathic changes that were predominant in proximal muscles, although EMG performed at birth was normal in two patients. Brief bursts of high-frequency repetitive discharges were electrically elicited in four patients. Uniformly slowed motor NCVs without signs of denervation were observed in seven patients: five merosin-deficient, one merosin-positive, and one with unavailable merosin status. The merosin-deficient neuropathy also involved sensory nerves in three patients and worsened with age in two. In conclusion, myopathic EMG changes were typical and early findings in all types of CMD. An associated neuropathy was detected in most patients with merosin-deficient CMD, and also in a child with normal merosin expression.

New FKRP mutations causing congenital muscular dystrophy associated with mental retardation and central nervous system abnormalities. Identification of a founder mutation in Tunisian families

The congenital muscular dystrophies (CMD) constitute a clinically and genetically heterogeneous group of autosomal recessive myopathies. Patients show congenital hypotonia, muscle weakness, and dystrophic changes on muscle biopsy. Mutations in four genes (FKT1, POMGnT1, POMT1, FKRP) encoding putative glycosyltransferases have been identified in a subset of patients characterized by a deficient glycosylation of alpha-dystroglycan on muscle biopsy. FKRP mutations account for a broad spectrum of patients with muscular dystrophy, from a severe congenital form with or without mental retardation (MDC1C) to a much milder limb-girdle muscular dystrophy (LGMD2I). We identified two novel homozygous missense FKRP mutations, one, A455D, in six unrelated Tunisian patients and the other, V405L, in an Algerian boy. The patients, between the ages of 3 and 12 years, presented with a severe form of MDC1C with calf hypertrophy and high serum creatine kinase levels. None had ever walked. Two had cardiac dysfunction and one strabismus. They all had mental retardation, microcephaly, cerebellar cysts, and hypoplasia of the vermis. White matter abnormalities were found in five, mostly when cranial magnetic resonance imaging was performed at a young age. These abnormalities were shown to regress in one patient, as has been observed in patients with Fukuyama CMD. Identification of a new microsatellite close to the FKRP gene allowed us to confirm the founder origin of the Tunisian mutation. These results strongly suggest that particular FKRP mutations in the homozygous state induce structural and clinical neurological lesions in addition to muscular dystrophy. They also relate MDC1C to other CMD with abnormal protein glycosylation and disordered brain function.