From case to caution: hyponatremia in a patient with Duchenne muscular dystrophy on vamorolone and lessons for clinicians

Long-term glucocorticoid therapy is the mainstay of treatment for individuals with Duchenne muscular dystrophy (DMD) but confers significant side effects. Vamorolone, a novel dissociative glucocorticoid for DMD, has similar anti-inflammatory effects on muscle, while sparing some adverse effects. It causes adrenal suppression but uniquely acts as a mineralocorticoid antagonist. We report a patient with DMD who switched from daily deflazacort to vamorolone at age 13.0 years. Six months later, he developed fever, vomiting, and diarrhea, necessitating oral hydrocortisone stress dosing. He presented to hospital, where he was hypotensive, hyponatremic (119 mmol/L), and mildly hyperkalemic. He received 3 days of intravenous hydrocortisone and fluids. Lisinopril and spironolactone were withheld. This case raised concern for an adrenal crisis, manifested by mineralocorticoid deficiency. It highlights the importance of stress dosing and checking electrolytes during illness when on vamorolone, especially if on cardiac medications, and education of patients, families, and multidisciplinary healthcare providers.