Efficacy of methylphenidate treatment in childhood myotonic dystrophy type 1 and comorbid attention deficit hyperactivity disorder: A case report using eye tracking assessment.

INTRODUCTION: Despite the increased prevalence of comorbid attention deficit hyperactivity disorder (ADHD) in children with myotonic dystrophy type 1, the effects of methylphenidate treatment on associated cognitive deficits in this population is not yet investigated. CASE: We describe a case study of an eleven-year-old male patient with myotonic dystrophy type 1 and comorbid ADHD that was treated with methylphenidate in a twice daily regime (0.60 mg/kg/day). Positive effects on learning and cognition were reported by the parents and teachers. No negative side effects were reported. Sequential neuropsychological assessments before and 45 minutes after methylphenidate intake were conducted to quantify the cognitive effects of methylphenidate treatment. Significant improvements in regulation of attention were behaviorally observed and were quantified using eye tracking technology. CONCLUSION: We conclude that methylphenidate may be an effective treatment for ADHD-related cognitive deficits and learning difficulties in children with myotonic dystrophy type 1 which merits further research.

Successful treatment of a patient with statin-induced myopathy and myotonic dystrophy type II with proprotein convertase subtilisin/kexin type 9 inhibitor, alirocumab (Praluent).

Presently there are limited treatment options for hypercholesterolemia in patients with statin intolerance and myotonic dystrophy. A 74 year-old male presented to endocrine clinic with hypercholesterolemia (serum LDL-C 210 mg/dL), hypogonadism, insulin-controlled type 2 diabetes mellitus, and minimally elevated serum creatine kinase (CK) levels (184 U/L, ref. range 38-174). Shortly after simvastatin treatment, patient developed severe myalgias in the proximal lower and upper extremities; and serum CK increased to 317 U/L. Subsequently patient was treated with various statins including rosuvastatin with similar outcomes. Patient was also treated with bile acid binding resin and ezetimibe without improvement. At this time, a diagnosis of myotonic dystrophy type 2 was confirmed. Patient was then treated with alirocumab, a PCSK9 inhibitor 75 mg subcutaneously every 2 weeks with significant improvement in LDL-C (90 mg/dL) and myalgias. In conclusion, PCSK9 inhibitors such as alirocumab may be an excellent lipid lowering agent in patients with statin intolerance and myotonic dystrophy.

Ritodrine-induced rhabdomyolysis, infantile myotonic dystrophy, and maternal myotonic dystrophy unveiled.

A primiparous pregnant woman in remission of myositis suffered very acute-onset ritodrine-induced rhabdomyolysis. At 29 gestational weeks, ritodrine was administered for threatened preterm labor. Just 3 h later, she complained of severe limb muscle pain, with serum creatinine phosphokinase elevated to 32 019 U/L and myoglobinuria. The muscle pain disappeared immediately after ceasing administration of ritodrine. At 31 weeks, premature rupture of the membranes occurred, necessitating cesarean section, yielding a baby with weak tonus, and the presence of infantile muscle diseases was suspected. Genetic analysis of the infant confirmed myotonic dystrophy (dystrophia myotonica, DM), which prompted us to perform maternal genetic analysis, confirming maternal DM. Ritodrine can induce rhabdomyolysis even in the prodromal phase with a mild phenotype of DM. A literature review suggested that ritodrine-induced rhabdomyolysis may be likely to occur more acutely after ritodrine administration in DM compared with non-DM mothers.

Calcium increase in mouse skeletal muscles by triparanol: a drug to induce myotonic dystrophy-like clinical manifestations.

Triparanol (Trp) is known to cause clinical features similar to those seen in myotonic dystrophy, including myotonia, cataract and baldness. To explore the pathophysiological mechanism of myotonic dystrophy, we examined the effect of Trp on intracellular calcium in cultured skeletal myoblasts and myotubes as well as cardiac myocytes by using a fluorescent indicator. Trp preferentially induced increase of intracellular calcium in myotubes of skeletal muscles. Since the increase of calcium was inhibited by thapsigargin pretreatment but not by extracellular calcium elimination, it appears that triparanol might act mostly on intracellular calcium stores. Trp also inhibited the increase of calcium in myotubes induced by acetylcholine. Trp might cause myotonia possibly through the increase of intracellular calcium from intracellular stores.

Myotonic muscular dystrophy associated with ritodrine tocolysis.

A patient thought to be normal was admitted with premature labor at 29+ weeks' gestation. Treatment with the beta-mimetic ritodrine hydrochloride appeared to provoke symptoms of myotonic muscular dystrophy. Neurological history and examination confirmed the presence of previously unsuspected myotonic dystrophy in the patient, her father, and paternal grandfather. Discontinuation of the drug led to improvement in myotonia symptoms but worsening premature labor. Magnesium sulfate did not provoke the same symptoms but was unsuccessful in controlling premature contractions. Long-term management with bed rest, phenytoin, and isoxsuprine hydrochloride resulted in term delivery. Subsequently, maternal symptoms of myotonia disappeared. Congenital myotonia was suspected in the fetus because of the ultrasonic demonstration of polyhydramnios and reduced fetal movements. This was confirmed at delivery. The mechanism by which ritodrine unmasked the myotonia is unclear but may be related to changes in the cell membrane (chloride conductance, the sodium-potassium pump, or membrane polarization).

Myotonia precipitated by propranolol therapy.

A 39-year-old man with ischaemic heart-disease developed clinical myotonia while taking propranolol. The myotonia disappeared when administration of the drug ceased. The patient appears to have dystrophia myotonica which had not been evident before propranolol therapy.