Use of dexamethasone in idiopathic, acute pediatric rhabdomyolysis

Current rhabdomyolysis treatment guidelines vary based on the etiology and diagnosis, yet many cases evade conclusive diagnosis. In these cases, treatment options remain largely limited to fluids and supportive therapy. We present two cases of acute rhabdomyolysis diagnosed in the emergency department: a 5-year-old boy with sudden onset bilateral flank pain, and a 13-year-old boy with 2-3 days of worsening pectoral and shoulder pain. Each patient had a prior similar episode requiring hospitalization in the past. The 5-year-old had no inciting trauma or trigger, medication use, or illness. The 13-year-old previously had an upper respiratory infection during the week prior and had been strenuously exercising at the time of onset. Genetic testing results were unknown for both patients during their hospitalizations, and insurance and other barriers led to delay. Later results for the first patient revealed a heterozygous deletion in intron 19 on the LPIN1 gene interpreted as a variant of unknown significance. During their hospitalizations, both children were started on intravenous (i.v.) fluids, and creatine kinase (CK) initially trended downward, but then began to rise or plateau. After reviewing the cases, prior literature, and anecdotal evidence of benefit from corticosteroid therapy in rhabdomyolysis with our consultant metabolic physicians, dexamethasone was initiated. In both patients, dexamethasone use correlated with relief of patient symptoms, significantly decreased CK value, and our ability to discharge these patients home quickly. Our cases, discussion, and literature review all lead to the consideration of the use of dexamethasone in conjunction with standard therapy for acute rhabdomyolysis.

Mitochondrial energetic impairment in a patient with late-onset glutaric acidemia Type 2

Glutaric acidemia type 2 (GA2), also called multiple acyl-CoA dehydrogenase deficiency, is an autosomal recessive disorder of fatty acid, amino acid, and choline metabolism resulting in excretion of multiple organic acids and glycine conjugates as well as elevation of various plasma acylcarnitine species (C4-C18). It is caused by mutations in the ETFA, ETFB, or ETFDH genes which are involved in the transfer of electrons from 11 flavin-containing dehydrogenases to Coenzyme Q₁₀ (CoQ₁₀ ) of the mitochondrial electron transport chain (ETC). We report a patient who was originally reported as the first case with primary myopathic CoQ₁₀ deficiency when he presented at 11.5 years with exercise intolerance and myopathy that improved after treatment with ubiquinone and carnitine. At age 23, his symptoms relapsed despite increasing doses of ubiquinone and he was shown to have biallelic mutations in the ETFDH gene. Treatment with riboflavin was started and ubiquinone was changed to ubiquinol. After 4 months, the patient recovered his muscle strength with normalization of laboratory exams and exercise tolerance. Functional studies on fibroblasts revealed decreased levels of ETFDH as well as of very long-chain acyl-CoA dehydrogenase and trifunctional protein α. In addition, the mitochondrial mass was decreased, with increased formation of reactive oxygen species and oxygen consumption rate, but with a decreased spared respiratory capacity, and decreased adenosine triphosphate level. These findings of widespread dysfunction of fatty acid oxidation and ETC enzymes support the impairment of a larger mitochondrial ETC supercomplex in our patient.

Genetic considerations for adults with congenital heart disease

Congenital heart disease (CHD) remains the most common birth defect, with an estimated incidence of approximately 1% of all births. The population of adults with CHD is growing rapidly with advances in medical care. Overall survival to adulthood in the current era estimated to exceed 90%. Genetic causes of CHD can be classified into several broad categories: (a) chromosomal aneuploidy, (b) large chromosomal deletion or duplication, (c) single gene mutation, and (d) copy number variation. However, only 20-30% of CHD cases have an established etiology characterized by either genetic abnormalities or environmental factors. The role of genetics in the field of adult CHD is only increasing. More adult patients with CHD are seeking genetic counseling to understand the etiology of their underlying CHD and the risks to future offspring. A multidisciplinary approach is essential to provide appropriate counseling to patients regarding indications for genetic testing and interpretations of results. Novel advances with precision medicine may soon enable clinicians to individualize therapies for a comprehensive approach to the care of adult patients with CHD.