Immunohistological intensity measurements as a tool to assess sarcolemma-associated protein expression.

AIMS: The quantification of protein levels in muscle biopsies is of particular relevance in the diagnostic process of neuromuscular diseases, but is difficult to assess in cases of partial protein deficiency, particularly when information on protein localization is required. The combination of immunohistochemistry and Western blotting is often used in these cases, but is not always possible if the sample is scarce. We therefore sought to develop a method to quantify relative levels of sarcolemma-associated proteins using digitally captured images of immunolabelled sections of skeletal muscle. METHODS: To validate our relative quantification method, we labelled dystrophin and other sarcolemmal proteins in transverse sections of muscle biopsies taken from Duchenne muscular dystrophy and Becker muscular dystrophy patients, a manifesting carrier of Duchenne muscular dystrophy and normal controls. RESULTS: Using this method to quantify relative sarcolemmal protein abundance, we were able to accurately distinguish between the different patients on the basis of the relative amount of dystrophin present. CONCLUSIONS: This comparative method adds value to techniques that are already part of the diagnostic process and can be used with minimal variation of the standardized protocols, without using extra amounts of valuable biopsy samples. Comparative quantification of sarcolemmal proteins on immunostained muscle sections will be of use to establish both the abundance and localization of the protein. Moreover, it can be applied to assess the efficacy of experimental therapies where only partial restoration or upregulation of the protein may occur.

Congenital myasthenic syndromes in childhood: diagnostic and management challenges.

The Congenital Myasthenic Syndromes (CMS), a group of heterogeneous genetic disorders of neuromuscular transmission, are often misdiagnosed as congenital muscular dystrophy (CMD) or myopathies and present particular management problems. We present our experience of 46 children with CMS, referred to us between 1992-2007 with provisional diagnoses of congenital myopathy (22/46), CMS or limb-girdle myasthenia (9/46), central hypotonia or neurometabolic disease (5/46), myasthenia gravis (4/46), limb-girdle or congenital muscular dystrophy (4/46) and SMA (2/46). Diagnosis was often considerably delayed (up to 18y4 m), despite the early symptoms in most cases. Diagnostic clues in the neonates were feeding difficulties (29/46), hypotonia with or without limb weakness (21/46), ptosis (19/46), respiratory insufficiency (12/46), contractures (4/46) and stridor (6/46). Twenty-five children had delayed motor milestones. Fatigability developed in 43 and a variable degree of ptosis was eventually present in 40. Over the period of the study, the mainstay of EMG diagnosis evolved from repetitive nerve stimulation to stimulation single fibre EMG. The patients were studied by several different operators. 66 EMGs were performed in 40 children, 29 showed a neuromuscular junction abnormality, 7 were myopathic, 2 had possible neurogenic changes and 28 were normal or inconclusive. A repetitive CMAP was detected in only one of seven children with a COLQ mutation and neither of the two children with Slow Channel Syndrome mutations. Mutations have been identified so far in 32/46 children: 10 RAPSN, 7 COLQ, 6 CHRNE, 7 DOK7, 1 CHRNA1 and 1 CHAT. 24 of 25 muscle biopsies showed myopathic changes with fibre size variation; 14 had type-1 fibre predominance. Three cases showed small type-1 fibres resembling fibre type disproportion, and four showed core-like lesions. No specific myopathic features were associated with any of the genes. Twenty children responded to Pyridostigmine treatment alone, 11 to Pyridostigmine with either 3, 4 DAP or Ephedrine and five to Ephedrine alone. Twenty one children required acute or chronic respiratory support, with tracheostomy in 4 and nocturnal or emergency non-invasive ventilation in 9. Eight children had gastrostomy. Another 11 were underweight for height indicative of failure to thrive and required dietetic input. A high index of clinical suspicion, repeat EMG by an experienced electromyographer and, if necessary, a therapeutic trial of Pyridostigmine facilitates the diagnosis of CMS with subsequent molecular genetic confirmation. This guides rational therapy and multidisciplinary management, which may be crucial for survival, particularly in pedigrees where previous deaths have occurred in infancy.

Swallowing difficulties in Duchenne muscular dystrophy: indications for feeding assessment and outcome of videofluroscopic swallow studies.

Feeding difficulties are known to occur with advancing age in Duchenne muscular dystrophy (DMD). We evaluated the role of videofluoroscopy swallow study (VFSS) in a group of 30 DMD patients with feeding difficulties. Indications for feeding assessment were: respiratory infections potentially attributable to aspiration (n=10) and/or episodes of choking (n=24) subdivided into isolated choking events (n=8) and regular choking during swallowing (n=16). Indications for assessment were analysed in relation to the VFSS results. Median age at assessment was 17.13 years (range 6-31.4). Twenty-four VFSS were performed. Prolonged chewing and effortful bolus transport for solids increased with age. Swallow trigger was normal in the majority of cases. All patients had some post-swallow pharyngeal residue around the laryngeal inlet increasing in volume with age. Although this residue did not result in aspiration, it was worse in patients that were frequently choking. Three patients intermittently had penetration of the supraglottic space that did not reach the vocal folds during the swallow. Our results suggest that reported swallowing problems when assessed are not always associated with difficulties on VFSS. It is the oral phase of swallowing that is most significantly affected in DMD. The pharyngeal phase is well triggered but is weak with incomplete pharyngeal clearance leaving pharyngeal residue. Insufficient or effortful chewing coupled with weak clearance may predispose them to choking episodes either as a one off event or with increasing frequency with age. This study suggests that VFSS may not be of additional benefit to careful feeding history and observation in DMD with feeding difficulties.

Comparative analysis of antisense oligonucleotide sequences for targeted skipping of exon 51 during dystrophin pre-mRNA splicing in human muscle.

Duchenne muscular dystrophy (DMD) is caused by mutations in the dystrophin gene that result in the absence of functional protein. In the majority of cases these are out-of-frame deletions that disrupt the reading frame. Several attempts have been made to restore the dystrophin mRNA reading frame by modulation of pre-mRNA splicing with antisense oligonucleotides (AOs), demonstrating success in cultured cells, muscle explants, and animal models. We are preparing for a phase I/IIa clinical trial aimed at assessing the safety and effect of locally administered AOs designed to inhibit inclusion of exon 51 into the mature mRNA by the splicing machinery, a process known as exon skipping. Here, we describe a series of systematic experiments to validate the sequence and chemistry of the exon 51 AO reagent selected to go forward into the clinical trial planned in the United Kingdom. Eight specific AO sequences targeting exon 51 were tested in two different chemical forms and in three different preclinical models: cultured human muscle cells and explants (wild type and DMD), and local in vivo administration in transgenic mice harboring the entire human DMD locus. Data have been validated independently in the different model systems used, and the studies describe a rational collaborative path for the preclinical selection of AOs for evaluation in future clinical trials.

A congenital myopathy with diaphragmatic weakness not linked to the SMARD1 locus.

Severe diaphragmatic weakness in infancy is rare. Common causes include structural myopathies, neuromuscular transmission defects, or anterior horn cell dysfunction (spinal muscular atrophy with respiratory distress, SMARD1). We describe a form of infantile diaphragmatic weakness without mutations in the SMARD1 gene, in which pathological and clinical features differ from known conditions, and investigations suggest a myopathy. We identified seven cases in four families. All presented soon after birth with feeding and breathing difficulties, marked head lag, facial weakness, and preserved antigravity movements in the limbs, with arms weaker than legs. All had paradoxical breathing and paralysis of at least one hemi-diaphragm. All required gastrostomy feeding, and all became ventilator-dependent. Investigations included myopathic EMG, muscle biopsy showing myopathic changes, normal electrophysiology and no mutations in SMN1 or IGHMBP2. These seven infants are affected by a myopathic condition clinically resembling SMARD1. However, its pathogenesis appears to be a myopathy affecting predominantly the diaphragm.

Predictive factors for the development of scoliosis in Duchenne muscular dystrophy.

OBJECTIVE: Scoliosis is a frequent complication (68-90%) of Duchenne muscular dystrophy (DMD). Prevention of limb deformities, rehabilitation in knee-ankle-foot-orthoses (KAFOs) and glucocorticoids prolong walking and standing, and might reduce scoliosis. We evaluated possible predictive factors for scoliosis development in a large DMD population. METHODS: Case notes of 123 DMD boys, > or = 17 years, followed at our centre between 1992 and 2002 were reviewed. Univariate analysis was used to relate two outcome measures (age at onset of scoliosis and severity at 17 years) with (i) glucocorticoids treatment; (ii) ages at (a) loss of independent ambulation, (b) rehabilitation into KAFOs, (c) loss of standing, (iii) forced vital capacity (FVC) (%) between 11 and 12 years and (iv) lower limb contractures. RESULTS: In total, 37/123 boys (30%) received intermittent prednisolone (0.75 mg/kg/day, 10 day/month) for a median 1-year (2 months-9 years), starting between 7.7 and 12.4 years (mean 9.5). About 96/123 (78%) were rehabilitated into KAFOs at 10.2+/-1.6 years. Age at loss of ambulation in KAFOs was 12.3+/-1.9 years and at loss of standing 12.8+/-2.1 years. About 95/123 (77%) boys developed scoliosis (Cobb angle >30 degrees ). Mean age+/-S.D. at scoliosis onset was 12.7+/-1.6 years. Forty-three boys (35%) had scoliosis surgery by 15+/-1.2 years. Later age at loss of ambulation (p<0.0001) and longer duration of prednisolone treatment (p=0.01) related to later scoliosis onset. Ages at loss of ambulation and standing were inversely related to scoliosis severity at 17 years (p<0.005). Hip asymmetry and %FVC at 11-12 years were directly related to scoliosis severity (p=0.02). CONCLUSIONS: Our data indicate a significant association between prolonged ambulation and a reduced risk of scoliosis development. Glucocorticoid administration, in our series, appear to be associated with a later onset of scoliosis, but did not alter the severity at 17 years, probably reflecting the shorter overall glucocorticoid exposure in this population.

Muscular dystrophies due to defective glycosylation of dystroglycan.

Muscular dystrophies are a clinically and genetically heterogeneous group of disorders. Until recently most of the proteins associated with muscular dystrophies were believed to be proteins of the sarcolemma associated with reinforcing the plasma membrane or in facilitating its re-sealing following injury. In the last few years a novel and frequent pathogenic mechanism has been identified that involves the abnormal glycosylation of alpha-dystroglycan (ADG). This peripheral membrane protein undergoes complex and crucial glycosylation steps that enable it to interact with LG domain containing extracellular matrix proteins such as laminins, agrin and perlecan. Mutations in six genes (POMT1, POMT2, POMGnT1, fukutin, FKRP and LARGE) have been identified in patients with reduced glycosylation of ADG. While initially a clear correlation between gene defect and phenotype was observed for each of these 6 genes (for example, Walker Warburg syndrome was associated with mutations in POMT1 and POMT2, Fukuyama congenital muscular dystrophy associated with fukutin mutations, and Muscle Eye Brain disease associated with POMGnT1 mutations), we have recently demonstrated that allelic mutations in each of these 6 genes can result in a much wider spectrum of clinical conditions. Thus, the crucial aspect in determining the phenotypic severity is not which gene is primarily mutated, but how severely the mutation affects the glycosylation of ADG. Systematic mutation analysis of these 6 glycosyltransferases in patients with a dystroglycan glycosylation disorder identifies mutations in approximately 65% suggesting that more genes have yet to be identified.

Pilot trial of albuterol in spinal muscular atrophy.

The aim of this pilot study was to evaluate the effect of albuterol in children with spinal muscular atrophy (SMA). Thirteen patients (five with SMA II and eight with SMA III) were given oral albuterol for 6 months. There was a significant increase in myometry, forced vital capacity, and lean body mass between the baseline and the 6-month assessments (p < 0.05). Albuterol may have a beneficial effect in patients with SMA without causing any significant adverse effects. Larger randomized, placebo-controlled trials are needed to confirm this observation.

Collagen VI involvement in Ullrich syndrome: a clinical, genetic, and immunohistochemical study.

BACKGROUND: Ullrich congenital muscular dystrophy (UCMD) is a form of merosin-positive congenital muscular dystrophy characterized by proximal contractures, distal laxity, rigidity of the spine, and respiratory complications. Recently, a deficiency of collagen VI on muscle and skin biopsy together with recessive mutations in the collagen 6A2 gene were reported in three families with UCMD. However, the clinical spectrum, frequency, and level of heterogeneity of this disorder are not known. SUBJECTS AND METHODS: The authors studied 15 patients (aged 3 to 23.6 years) with a clinical diagnosis of UCMD. Linkage analysis to the three collagen VI genes was performed in all informative families (n = 7), whereas immunohistochemical analysis of collagen VI expression in muscle was performed in the remaining cases. RESULTS: An immunocytochemical reduction of collagen VI was observed in six patients. Three of the six patients belonged to informative families, and haplotype analysis clearly suggested linkage to the COL6A1/2 locus in two cases and to the COL6A3 loci in the third case. In the remaining nine patients, primary collagen VI involvement was excluded based on either the linkage analysis (four families) or considered unlikely based on normal immunolabeling of collagen VI. Age and presentation at onset, the distribution and severity of weakness and contractures, and the frequency of nonambulant patients were similar in the patients with and without collagen VI involvement. Distal laxity, rigidity of the spine, scoliosis, failure to thrive, and early and severe respiratory impairment were found in all patients by the end of the first decade of life, irrespective of their maximum motor functional ability or their collagen status. CONCLUSIONS: These results suggest that collagen VI involvement is relatively common in UCMD (40%); however, the role of this molecule was excluded in a number of cases, suggesting genetic heterogeneity of this condition.

Congenital form of spinal muscular atrophy predominantly affecting the lower limbs: a clinical and muscle MRI study.

We describe clinical and muscle magnetic resonance imaging (MRI) findings in 11 cases (three familial and eight sporadic) with the form of spinal muscular atrophy characterised by predominant involvement of the lower limbs with weakness of the proximal and distal muscles and marked atrophy of the distal leg and foot muscles. All patients presented at birth with talipes, which were in extension in seven of the 11. Arm muscle and function were preserved and lower limbs appeared to be disproportionately shorter compared to trunk and upper limbs. Functional abilities were markedly affected and only one of the 11 is able to walk independently for long distances, while six require support of crutches and two use callipers for walking. One child lost ambulation following a fall. The course of the disease is relatively stable and the progression of disability appeared to be related mostly to increased contractures rather than to loss of muscle strength. Respiratory and cardiac function were well preserved. A neurogenic disorder was suggested by electromyography and/or muscle biopsy in all patients, while motor nerve conduction was consistently normal. Muscle MRI of the thighs revealed diffuse atrophic appearance with relative hypertrophy of the adductor longus and of the semitendinosus. Genetic studies excluded the involvement of the survival motor neuron gene but none of these families was sufficiently informative to study linkage to the locus on chromosome 12q23-q24 previously found to be involved in patients with similar phenotype. In our experience this form of spinal muscular atrophy affecting predominantly the lower limbs is a relatively common form and should be considered in the differential diagnosis of infants with talipes and weakness in the lower limbs. The identical clinical and imaging features of the sporadic and familial cases suggest that these cases are likely to be affected by the same condition.

Expanding the phenotype of potassium channelopathy: severe neuromyotonia and skeletal deformities without prominent Episodic Ataxia.

We report an unusual family in which the same point mutation in the voltage-gated potassium channel gene KCNA1 resulted in markedly different clinical phenotypes. The propositus presented in infancy with marked muscle stiffness, motor developmental delay, short stature, skeletal deformities, muscle hypertrophy and muscle rippling on percussion. He did not experience episodic ataxia. His mother presented some years later with typical features of Episodic Ataxia type 1 (EA1), with episodes of ataxia lasting a few minutes provoked by exercise. On examination she had myokymia, joint contractures and mild skeletal deformities. A heterozygous point mutation in the voltage-gated K(+) channel (KCNA1) gene (ACG-AGG, Thr226Arg) was found in both. We conclude that mutations in the potassium channel gene (KCNA1) can cause severe neuromyotonia resulting in marked skeletal deformities even if episodic ataxia is not prominent.

Muscle magnetic resonance imaging in patients with congenital muscular dystrophy and Ullrich phenotype.

The aim of this study was to evaluate muscle magnetic resonance imaging findings in patients with congenital muscular dystrophy and Ullrich phenotype. Fifteen children with congenital muscular dystrophy and Ullrich phenotype were included in the study. All patients had collagen VI studies in muscle and, when family structure was informative, linkage studies to the collagen 6 loci. Three of the 15 patients had reduced collagen in muscle. One of the three was from an informative family and linked to one of the collagen 6 loci. Another patient was linked to one of the collagen 6 loci but had normal expression of collagen in muscle. The remaining 11 all had normal collagen expression in muscle. Only two of these 11 were from informative families and linkage to collagen 6 loci was excluded in them. All patients had muscle magnetic resonance imaging of their leg muscles using transverse T1 sequences. With the exception of the two patients in whom linkage to the collagen 6 loci was excluded, the other 13 patients showed the same pattern of selective involvement on magnetic resonance imaging of thigh muscles. This consisted of relative sparing of sartorius, gracilis, adductor longus and rectus. This pattern was also found in the case linked COL6A1/A2 locus but with normal collagen. This finding, and the striking clinical and magnetic resonance imaging concordance between patients with normal and reduced collagen VI in muscle suggest that collagen VI could still be the culprit in several cases with normal collagen expression, or alternatively a primary defect in a protein that closely interacts with collagen VI. Mutation analysis of the collagen 6 genes in cases with normal collagen VI expression is needed to resolve this issue.

Remission of clinical signs in early duchenne muscular dystrophy on intermittent low-dosage prednisolone therapy.

We report a 5-year follow-up of two 4-year-old boys with classical Duchenne dystrophy, with an out-of-frame deletion in the Duchenne gene and absence of dystrophin in their muscle, who had a quite remarkable response to an intermittent, low-dosage, regime of prednisolone (0.75 mg/kg/day for 10 days each month, or alternating 10 days on and 10 days off). In the first case there was complete remission of all clinical signs of dystrophy, sustained almost fully up to the present time; in the second, the initial response was almost as marked, sustained for almost 5 years, before showing a fairly rapid decline over the ensuing year that resulted in loss of independent ambulation at the age of 10. Both boys remained around the 50th centile for height and weight, and showed no evidence of demineralization of bone on consecutive dual X-ray absorptiometry scanning of the spine, nor any signs of chronic prednisolone toxicity. These carefully documented individual cases suggest there may be an optimal window for treatment in the early stages of the disease, and further larger scale controlled studies should be targeted more selectively at this stage of the disease. This report also confirms that our regime of low dosage, intermittent prednisolone, with cycles of 10 days of treatment, either per month or alternating with 10 days off treatment, is well tolerated and can therefore be recommended for long-term use in children with Duchenne muscular dystrophy.

Diagnostic difficulties in a case of primary systemic carnitine deficiency with idiopathic dilated cardiomyopathy.

Blood spot carnitine profiles are widely used to screen for disorders of fatty acid oxidation. This case report emphasizes that a borderline concentration of free carnitine does not exclude the diagnosis of primary carnitine deficiency. Concurrent measurement of carnitine in the plasma and urine is a more sensitive test.

Prediction of prolonged ventilator dependence in children by respiratory function measurements.

Complications of ventilatory support are more common if this assistance is prolonged. Our aim was to determine if results of respiratory function measurement on the first day of ventilation identified children who would develop prolonged ventilatory dependence (> or = 4 days) and whether such results were a more accurate predictor than readily available clinical data. Thirty three children, median age 2 years (range 0.1-13.6), who were supported by a constant flow ventilator and hence had measurements of compliance of the respiratory system (CRS) and resistance of the respiratory system (RRS) on the first day of ventilatory support, were retrospectively identified. Those who needed prolonged ventilatory support had a lower CRS on day one (p < 0.01) and required at any time during their ventilatory career both a higher maximum inspired oxygen concentration (p < 0.01) and peak inspiratory pressure (PIP) (p < 0.01). Logistic regression analysis demonstrated that only a low CRS and high maximum PIP were significantly correlated with prolonged ventilator dependence. A low CRS (<0.4 (ml/cmH2O) kg(-1)) and a high maximum PIP (>27 cmH2O) had similar sensitivities (83%) and specificities (71% and 67% respectively) in predicting prolonged ventilatory dependence. The CRS results, unlike the maximum PIP results, however, were always available on the first day of ventilatory support. We therefore conclude that respiratory function measurements have a role in identifying children who would benefit from strategies to prevent prolonged ventilator dependence.

Muscle histology vs MRI in Duchenne muscular dystrophy.

OBJECTIVE: There are currently no effective treatments to halt the muscle breakdown in Duchenne muscular dystrophy (DMD), although genetic-based clinical trials are being piloted. Most of these trials have as an endpoint the restoration of dystrophin in muscle fibers, hence requiring sufficiently well-preserved muscle of recruited patients. The choice of the muscles to be studied and the role of noninvasive methods to assess muscle preservation therefore require further evaluation. METHODS: We studied the degree of muscle involvement in the lower leg muscles of 34 patients with DMD >8 years, using muscle MRI. In a subgroup of 15 patients we correlated the muscle MRI findings with the histology of open extensor digitorum brevis (EDB) muscle biopsies. Muscle MRI involvement was assigned using a scale 0-4 (normal-severe). RESULTS: In all patients we documented a gradient of involvement of the lower leg muscles: the posterior compartment (gastrocnemius > soleus) was most severely affected; the anterior compartment (tibialis anterior/posterior, popliteus, extensor digitorum longus) least affected. Muscle MRI showed EDB involvement that correlated with the patient's age (p = 0.055). We show a correlation between the MRI and EDB histopathologic changes, with MRI 3-4 grades associated with a more severe fibro-adipose tissue replacement. The EDB was sufficiently preserved for bulk and signal intensity in 18/22 wheelchair users aged 10-16.6 years. CONCLUSION: This study provides a detailed correlation between muscle histology and MRI changes in DMD and demonstrates the value of this imaging technique as a reliable tool for the selection of muscles in patients recruited into clinical trials.

Natural history of Ullrich congenital muscular dystrophy.

OBJECTIVE: To describe the course, complications, and prognosis of Ullrich congenital muscular dystrophy (UCMD), with special reference to life-changing events, including loss of ambulation, respiratory insufficiency, and death. METHODS: Review of the case notes of 13 patients with UCMD, aged 15 years or older at last visit, followed up at a tertiary neuromuscular centre, London, UK, from 1977 to 2007. Data collected were age at onset of symptoms, presenting symptoms, mobility, contractures, scoliosis, skin abnormalities, respiratory function, and feeding difficulties. RESULTS: The mean age at onset of symptoms was 12 months (SD 14 months). Eight patients (61.5%) acquired independent ambulation at a mean age of 1.7 years (SD 0.8 years). Nine patients (69.2%) became constant wheelchair users at a mean age of 11.1 years (SD 4.8 years). Three patients continued to ambulate indoors with assistance. Forced vital capacity (FVC) values were abnormal in all patients from age 6 years. The mean FVC (% predicted) declined at a mean rate of 2.6% (SD 4.1%) yearly. Nine patients (69.2%) started noninvasive ventilation at a mean age of 14.3 years (SD 5.0 years). Two patients died of respiratory insufficiency. CONCLUSION: In Ullrich congenital muscular dystrophy (UCMD), the decline in motor and respiratory functions is more rapid in the first decade of life. The deterioration is invariable, but not always correlated with age or severity at presentation. This information should be of help to better anticipate the difficulties encountered by patients with UCMD and in planning future therapeutic trials in this condition.

Update on the management of Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is familiar to paediatricians as the most common childhood muscular dystrophy and leads to severe disability and early death in the late teenage years if untreated. Improvements in general care, glucocorticoid corticosteroid treatment, non-invasive ventilatory support, and cardiomyopathy and scoliosis management have significantly changed the course of DMD in treated individuals, so that survival into adulthood is now a realistic possibility for most patients. This has important implications for the medical and social sectors involved in the transition to adult medical services and the provision of suitable employment and social care. Multidisciplinary team working for optimal management of DMD-specific multisystem complications is essential, and collaboration in disease specific national clinical networks is recommended. Several curative therapeutic strategies including cell and gene therapy are being pursued but are still at an experimental stage.

Randomized, double-blind, placebo-controlled trial of phenylbutyrate in spinal muscular atrophy.

OBJECTIVE: To assess the efficacy of phenylbutyrate (PB) in patients with spinal muscular atrophy in a randomized, double-blind, placebo-controlled trial involving 10 Italian centers. METHODS: One hundred seven children were assigned to receive PB (500 mg/kg/day) or matching placebo on an intermittent regimen (7 days on/7 days off) for 13 weeks. The Hammersmith functional motor scale (primary outcome measure), myometry, and forced vital capacity were assessed at baseline and at weeks 5 and 13. RESULTS: Between January and September 2004, 107 patients aged 30 to 154 months were enrolled. PB was well tolerated, with only one child withdrawing because of adverse events. Mean improvement in functional score was 0.60 in the PB arm and 0.73 in placebo arm (p = 0.70). Changes in the secondary endpoints were also similar in the two study arms. CONCLUSIONS: Phenylbutyrate was not effective at the regimen, schedule, and duration used in this study.