Respiratory outcomes in children with congenital myotonic dystrophy

PURPOSE: Congenital myotonic dystrophy (CDM) results in hypotonia and acute respiratory distress at birth. Previous studies show that prolonged periods of intubation (>4 weeks) correlate with increased mortality rates. The objective is to describe the use and duration of respiratory support in newborns with CDM and how these relate to mortality. METHODS: A retrospective chart review was performed at a tertiary pediatric hospital among children with confirmed diagnosis of CDM. The main outcome measures were: mortality, duration of invasive mechanical ventilation (IMV) and non-invasive partial pressure ventilation (NIPPV), along with long-term use of respiratory support and equipment. RESULTS: A total of 18 subjects met inclusion criteria, 83%.f which had documented respiratory distress at birth, 39%.equired NIPPV, and 50%.equired intubation in the neonatal period. The earliest NIPPV was initiated at day one of life, and the latest extubation to NIPPV was at 17 days of life. CONCLUSION: This cohort required IMV for shorter periods with earlier transitions to NIPPV which suggests a possible change in practice and earlier transition to NIPPV recently. Further data are needed to determine if there is a possible correlation between the need for NIPPV/IMV and mortality rates.

Congenital Phenotypes and DMPK CTG Repeat Number in Mothers and Children With Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is an autosomal dominant genetic disease. In DM1, the mutant allele expands during gametogenesis, and an extended CTG repeat sequence is inherited by the offspring. This often results in increased severity of DM1 symptoms in the affected offspring and may cause congenital myotonic dystrophy (CDM). This study aimed to clarify whether CTG repeat number predicts CDM in offspring. This retrospective study examined 14 women with DM1, their pregnancy and labor histories, and their 14 children diagnosed with DM1. There were 12 CDM patients and 2 non-CDM patients. Correlations between CDM onset and CTG repeat numbers of the mother and child were analyzed. Women who bore a child with CDM (infants with detected polyhydramnios during pregnancy, hypotonia, respiratory insufficiency, or suckling failure at birth) had a mean repeat number of 643 (standard deviation [SD] 436). For women who bore a child without CDM, the mean repeat number was 950 (SD 71), and no significant between-group difference was detected. The mean (SD) CTG repeat numbers observed in children with and without CDM were 1,646 (324) and 1,700 (565), respectively. CDM cannot be predicted based on the CTG repeat numbers of mothers or children.

microRNA-mRNA Profile of Skeletal Muscle Differentiation and Relevance to Congenital Myotonic Dystrophy

microRNAs (miRNAs) regulate messenger RNA (mRNA) abundance and translation during key developmental processes including muscle differentiation. Assessment of miRNA targets can provide insight into muscle biology and gene expression profiles altered by disease. mRNA and miRNA libraries were generated from C2C12 myoblasts during differentiation, and predicted miRNA targets were identified based on presence of miRNA binding sites and reciprocal expression. Seventeen miRNAs were differentially expressed at all time intervals (comparing days 0, 2, and 5) of differentiation. mRNA targets of differentially expressed miRNAs were enriched for functions related to calcium signaling and sarcomere formation. To evaluate this relationship in a disease state, we evaluated the miRNAs differentially expressed in human congenital myotonic dystrophy (CMD) myoblasts and compared with normal control. Seventy-four miRNAs were differentially expressed during healthy human myocyte maturation, of which only 12 were also up- or downregulated in CMD patient cells. The 62 miRNAs that were only differentially expressed in healthy cells were compared with differentiating C2C12 cells. Eighteen of the 62 were conserved in mouse and up- or down-regulated during mouse myoblast differentiation, and their C2C12 targets were enriched for functions related to muscle differentiation and contraction.

Bilateral diaphragmatic eventration and alveolar hypoventilation in congenital myotonic dystrophy

Context: Congenital myotonic dystrophy (CMD) is a subtype of type 1 myotonic dystrophy presented in the neonatal period associated with a 16–40% mortality rate. CMD cause significant morbidity and mortality and often require intensive intervention at birth because of hypotonia, respiratory failure and feeding difficulties. It can cause respiratory problems including ineffective cough, recurrent pulmonary infections, orthopnea, dyspnea, poor sleep, apnea and snoring. However, there are few descriptions about diaphragmatic impairment in CMD. We present a baby who had bilateral diaphragmatic eventration associated with CMD. Case report: A term outborn female baby with normal birth weight, delivered by cesarean presenting hypotonia and breathing difficulty since birth. There was no history of meconium aspiration syndrome and aspiration pneumonia. Neurological examination showed a severe hypotonia, eyelid ptosis, oral motor weakness and suction inability, without contractures. Chest X-rays confirmed the bilateral diaphragmatic paralysis. Electroneuromyography confirmed a marked myopathic involvement with frequent myotonic discharges. The mother presented clinical and electrical myotonic phenomena. The baby started mechanical ventilation as was not maintaining saturation on head box oxygen. After surgical repair the baby started on non-invasive respiratory support with improvement of ventilatory conditions. Conclusion: Diaphragmatic eventration is a congenital condition where the muscle maintains its normal costal attachments but is significantly elevated with limited motility. Clinical manifestations vary to life-threatening respiratory distress. Bilateral congenital diaphragmatic eventration is rarer and has more guarded prognosis. Early diaphragmatic plication enhances weaning process and may prevent or minimize the morbidity. Infants with CMD should be monitored for diaphragmatic impairment.