De novo variants in KLF7 are a potential novel cause of developmental delay/intellectual disability, neuromuscular and psychiatric symptoms.

Due to small numbers of reported patients with pathogenic variants in single genes, the phenotypic spectrum associated with genes causing neurodevelopmental disorders such as intellectual disability (ID) and autism spectrum disorder is expanding. Among these genes is KLF7 (Krüppel-like factor 7), which is located at 2q33.3 and has been implicated in several developmental processes. KLF7 has been proposed to be a candidate gene for the phenotype of autism features seen in patients with a 2q33.3q34 deletion. Herein, we report 4 unrelated individuals with de novo KLF7 missense variants who share similar clinical features of developmental delay/ID, hypotonia, feeding/swallowing issues, psychiatric features and neuromuscular symptoms, and add to the knowledge about the phenotypic spectrum associated with KLF7 haploinsufficiency.

Pentoxifylline as a rescue treatment for DMD: a randomized double-blind clinical trial.

OBJECTIVE: To determine whether pentoxifylline (PTX) slows the decline of muscle strength and function in ambulatory boys with Duchenne muscular dystrophy (DMD). METHODS: This was a multicenter, randomized, double-blinded, controlled trial comparing 12 months of daily treatment with PTX or placebo in corticosteroid-treated boys with DMD using a slow-release PTX formulation (~20 mg/kg/day). The primary outcome was the change in mean total quantitative muscle testing (QMT) score. Secondary outcomes included changes in QMT subscales, manual muscle strength, pulmonary function, and timed function tests. Outcomes were compared using Student t tests and a linear mixed-effects model. Adverse events (AEs) were compared using the Fisher exact test. RESULTS: A total of 64 boys with DMD with a mean age of 9.9 ± 2.9 years were randomly assigned to PTX or placebo in 11 participating Cooperative International Neuromuscular Research Group centers. There was no significant difference between PTX and the placebo group in total QMT scores (p = 0.14) or in most of the secondary outcomes after a 12-month treatment. The use of PTX was associated with mild to moderate gastrointestinal or hematologic AEs. CONCLUSION: The addition of PTX to corticosteroid-treated boys with DMD at a moderate to late ambulatory stage of disease did not improve or halt the deterioration of muscle strength and function over a 12-month study period. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that treatment with PTX does not prevent deterioration in muscle function or strength in corticosteroid-treated boys with DMD.

Randomized, blinded trial of weekend vs daily prednisone in Duchenne muscular dystrophy.

OBJECTIVE: To perform a double-blind, randomized study comparing efficacy and safety of daily and weekend prednisone in boys with Duchenne muscular dystrophy (DMD). METHODS: A total of 64 boys with DMD who were between 4 and 10 years of age were randomized at 1 of 12 centers of the Cooperative International Neuromuscular Research Group. Efficacy and safety of 2 prednisone schedules (daily 0.75 mg/kg/day and weekend 10 mg/kg/wk) were evaluated over 12 months. RESULTS: Equivalence was met for weekend and daily dosing of prednisone for the primary outcomes of quantitative muscle testing (QMT) arm score and QMT leg score. Secondary strength scores for QMT elbow flexors also showed equivalence between the 2 treatment groups. Overall side effect profiles of height and weight, bone density, cataract formation, blood pressure, and behavior, analyzed at 12 months, did not differ between weekend and daily dosing of prednisone. CONCLUSIONS: Weekend dosing of prednisone is equally beneficial to the standard daily dosing of prednisone. Analysis of side effect profiles demonstrated overall tolerability of both dosing regimens. CLASSIFICATION OF EVIDENCE: This study provides Class I evidence that weekend prednisone dosing is as safe and effective as daily prednisone in preserving muscle strength and preventing body mass index increases in boys with DMD over a 12-month period.

Pediatric sciatic neuropathies: a 30-year prospective study.

OBJECTIVE: The incidence, cause, and prognosis of sciatic neuropathy in children is not well understood. We report our 30-year experience of 53 patients with pediatric sciatic neuropathies (SN). METHODS: Prospective review of the history, physical examination, electrophysiologic findings, and clinical course of children with SN. RESULTS: The etiology of SN injury was varied and included trauma (13), iatrogenic causes (13) (8 orthopedic surgeries and 5 miscellaneous surgeries), prolonged extrinsic compression and immobilization (6), tumors (7), vascular (5), idiopathic and progressive (4), infantile and nonprogressive (2), and unknown, presumed postviral (3). Electrophysiologic studies demonstrated abnormalities in motor conduction studies of the peroneal nerve in 44/53 (83%) or tibial nerve in 35/51 (67%). Sensory conduction studies were abnormal in sural nerve in 34 of 43 cases (79%), and superficial peroneal nerves in 15/25 (60%). Needle EMG was abnormal in peroneal innervated muscles in all subjects, in tibial nerve innervated muscles in 43/51 (84%), and in the hamstrings in 18/29 (62%). Prognosis for recovery was variable and depended on the etiology and the severity of the nerve injury. CONCLUSIONS: SN is an uncommon mononeuropathy in children. The causes of SN are varied in children compared to adults. Electrophysiologic studies in children may be limited by poor tolerance but play an important role in establishing the diagnosis.

Allogeneic stem cell transplantation corrects biochemical derangements in MNGIE.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is a multisystemic autosomal recessive disease due to primary thymidine phosphorylase (TP) deficiency. To restore TP activity, we performed reduced intensity allogeneic stem cell transplantations (alloSCTs) in two patients. In the first, alloSCT failed to engraft, but the second achieved mixed donor chimerism, which partially restored buffy coat TP activity and lowered plasma nucleosides. Thus, alloSCT can correct biochemical abnormalities in the blood of patients with MNGIE, but clinical efficacy remains unproven.

PIP2 binding residues of Kir2.1 are common targets of mutations causing Andersen syndrome.

BACKGROUND: Mutations in KCNJ2, the gene encoding the inward-rectifying K+ channel Kir2.1, cause the cardiac, skeletal muscle, and developmental phenotypes of Andersen-Tawil syndrome (ATS; also known as Andersen syndrome). Although pathogenic mechanisms have been proposed for select mutations, a common mechanism has not been identified. METHODS: Seventeen probands presenting with symptoms characteristic of ATS were evaluated clinically and screened for mutations in KCNJ2. The results of mutation analysis were combined with those from previously studied subjects to assess the frequency with which KCNJ2 mutations cause ATS. RESULTS: Mutations in KCNJ2 were discovered in nine probands. These included six novel mutations (D71N, T75R, G146D, R189I, G300D, and R312C) as well as previously reported mutations R67W and R218W. Six probands possessed mutations of residues implicated in binding membrane-associated phosphatidylinositol 4,5-bisphosphate (PIP2). In total, mutations in PIP(2)-related residues accounted for disease in 18 of 29 (62%) reported KCNJ2 -based probands with ATS. Also reported is that mutation R67W causes the full clinical triad in two unrelated males. CONCLUSIONS: The novel mutations corresponding to residues involved in Kir2.1 channel-PIP2 interactions presented here as well as the overall frequency of mutations occurring in these residues indicate that defects in PIP2 binding constitute a major pathogenic mechanism of ATS. Furthermore, screening KCNJ2 in patients with the complex phenotypes of ATS was found to be invaluable in establishing or confirming a disease diagnosis as mutations in this gene can be identified in the majority of patients.

Severe autosomal recessive rippling muscle disease.

Rippling muscle disease (RMD) has previously been reported as a skeletal myopathy that was attributed to a defect in the sarcomere. Here we report a new form of RMD that is more severe, characterized by fatal arrhythmic cardiomyopathy and delayed bone age. Mortality has previously not been associated with RMD. With this report we hope to raise awareness that a subset of patients with this clinical entity are predisposed to severe cardiac disease.

Gentamicin treatment of Duchenne and Becker muscular dystrophy due to nonsense mutations.

Aminoglycosides have previously been shown to suppress nonsense mutations, allowing translation of full-length proteins in vitro and in animal models. In the mdx mouse, where muscular dystrophy is due to a nonsense mutation in the dystrophin gene, gentamicin suppressed truncation of the protein and ameliorated the phenotype. A subset of patients with Duchenne and Becker muscular dystrophy similarly possess a nonsense mutation, causing premature termination of dystrophin translation. Four such patients, with various stop codon sequences, were treated once daily with intravenous gentamicin at 7.5 mg/kg/day for 2 weeks. No ototoxicity or nephrotoxicity was detected. Full-length dystrophin was not detected in pre- and post-treatment muscle biopsies.

Clinical evaluator reliability for quantitative and manual muscle testing measures of strength in children.

Measurements of muscle strength in clinical trials of Duchenne muscular dystrophy have relied heavily on manual muscle testing (MMT). The high level of intra- and interrater variability of MMT compromises clinical study results. We compared the reliability of 12 clinical evaluators in performing MMT and quantitative muscle testing (QMT) on 12 children with muscular dystrophy. QMT was reliable, with an interclass correlation coefficient (ICC) of >0.9 for biceps and grip strength, and >0.8 for quadriceps strength. Training of both subjects and evaluators was easily accomplished. MMT was not as reliable, and required repeated training of evaluators to bring all groups to an ICC >0.75 for shoulder abduction, elbow and hip flexion, knee extension, and ankle dorsiflexion. We conclude that QMT shows greater reliability and is easier to implement than MMT. Consequently, QMT will be a superior measure of strength for use in pediatric, neuromuscular, multicenter clinical trials.

Pharmacologic and genetic therapy for childhood muscular dystrophies.

The outstanding advances in the molecular characterization of muscle diseases, including muscular dystrophies, inflammatory myopathies, and ion channel disorders, have resulted in the identification of potential targets for pharmacologic and genetic therapy in the best characterized of these diseases. The most common myopathy in children, Duchenne muscular dystrophy (DMD), is the focus of active pharmacologic clinical trials. Genetic transfer therapy research for this and other dystrophies is rapidly moving forward. However, as new approaches for treatment are being actively investigated, the current modality of treatment for all myopathies is still in the realm of physical medicine and rehabilitation. The focus of this review is on the advances in pharmacologic and genetic therapy research in DMD and limb girdle muscular dystrophies.

The mutation of Pro789 to Leu reduces the activity of the fast-twitch skeletal muscle sarco(endo)plasmic reticulum Ca2+ ATPase (SERCA1) and is associated with Brody disease.

Brody disease is a rare inherited disorder of fast-twitch skeletal muscle function and is characterized by a lifelong history of exercise-induced impairment of skeletal muscle relaxation, stiffness, and cramps. The autosomal recessive inheritance of mutations in ATP2A1, the gene encoding SERCA1, which is the fast-twitch skeletal muscle sarcoplasmic reticulum Ca2+ ATPase, has been associated with Brody disease in three of six Brody families in which ATP2A1 has been sequenced. In the present analysis of the ATP2A1 gene in four unrelated families with autosomal recessive inheritance of Brody disease, three mutations were found in two families, leading to premature stop codons and truncated SERCA1. In a third family, the homozygous substitution of T for C2366 led to the missense mutation of Pro789 to Leu. The Pro789 to Leu mutant was readily expressed in HEK-293 cells, but it demonstrated an almost complete loss of Ca2+ transport activity because of reduced Ca2+ affinity. In a fourth family, the heterozygous substitution of T for C2455, mutating Arg819 to Cys, was identified. This mutation was also readily expressed in HEK-293 cells and shown to have near normal Ca2+ transport activity, indicating that it is not causal for Brody disease. These results confirm the genetic heterogeneity of Brody disease and emphasize the importance of a functional test for mutant SERCA1; immunostaining of skeletal muscle to detect the loss of SERCA1a protein is not adequate for the diagnosis of ATP2A1-linked Brody disease.

Pediatric radial mononeuropathies: a clinical and electromyographic study of sixteen children with review of the literature.

Sixteen pediatric radial mononeuropathies were seen among 2077 electromyograms performed in the electromyography laboratory at The Children's Hospital, Boston, during 16.5 years, 1979-1995. Eight (50%) of these radial neuropathies, including 2 in newborns with apparent prenatal onset, were atraumatic, primarily related to compression in 6 and entrapment in 2. The other 8 (50%) were traumatic related to fractures or lacerations. Electromyography documented the radial neuropathy to be localized to the proximal main radial nerve trunk in 2 (13%), distal main radial nerve trunk in 9 (56%), and posterior interosseous nerve in 5 (31%) children. Significant improvement was noted in 13 of the 16 radial neuropathies--within 6-12 weeks for demyelinating lesions and up to 17 months for axonal injuries. Rarely, a child with a chronic progressive radial neuropathy or a postfracture radial neuropathy that does not improve in 3 months may require exploration.

Measurement of the concentrations of solutions through chromatic systems.

After a careful check of the response linearity of the spectrophotometer in absorbances and transmittances at wavelengths between 250 and 550 nm with potassium dichromate, the influence of the concentration of solutions on the tristimulus coordinates and the coordinates of the CIE 1931 (Commission Internationale de l'Éclairage) and CIELAB colorimetric systems was analyzed. How to use the value of only some chromatic coordinates to obtain a sample's concentration simultaneously is also shown.