INTRODUCTION: Cardiomyopathy in children carries a substantial risk of morbidity and mortality and is the primary indication for heart transplantation during childhood. Hypertrophic cardiomyopathy (HCM) in particular has been associated with premature death and reduced life expectancy, with reported annual incidence of 0.24–0.47 per 100,000 children. HCM is most often genetic and associated with inborn errors of metabolism, metabolic storage disorders or sarcomeric protein gene mutations. We present a case of acquired HCM leading to heart transplantation in an adolescent with severe undiagnosed hypothyroidism.
CASE DESCRIPTION: History: A previously healthy 14 year old female was admitted to the pediatric floor with progressively worsening chest pain, palpitations, and shortness of breath over the past 8 months. Family history was negative for sudden cardiac death, cardiomyopathy, and thyroid disorders. Physical exam: Her physical exam was significant for pallor, periorbital and peripheral pitting edema, laterally displaced point of maximal impulse, systolic murmur heard best at the lower left sternal border, and a pronounced S4. Labs and Imaging: Her labs were significant for an elevated NT-proBNP of 6687 pg/mL (nL = 1-178 pg/mL) with an elevated TSH > 1000 IU/mL (nL= 0.27 - 4.20 IU/mL). Her initial chest x-ray was significant for cardiomegaly without overt signs of pulmonary edema, and her EKG was significant for left axial deviation and left bundle branch block. Echocardiogram on admission revealed severely reduced left ventricular ejection fraction with severe concentric left ventricular hypertrophy (LVH) as well as dynamic left ventricular outlet obstruction( LVOT), and a small circumferential pericardial effusion. Given concern for the need for advanced therapies and further cardiac work-up, the patient was transferred to a tertiary center with a pediatric cardiac ICU. She underwent a right heart catheterization which showed elevated right sided filling pressures, elevated pulmonary arterial wedge pressure, as well as a depressed cardiac index. She required inotropic support, mechanical ventilation, and percutaneous left ventricular assist device (LVAD) as a bridge to eventual heart transplant. She was also started on synthroid with subsequent normalization of her TSH. The patient had a heart transplant 2 months after initial presentation, and she continues to follow with her transplant team. Diagnosis: Her final diagnosis was hypertrophic cardiomyopathy secondary to severe hypothyroidism.
DISCUSSION: Thyroid disorders are commonly associated with cardiac abnormalities, in particular left ventricular diastolic dysfunction. We present a unique case of HCM in the setting of severe hypothyroidism. In this case we believe that lack of early diagnosis may have contributed to the severity of LVOT and eventual need for heart transplant.
CONCLUSION: While most cases of HCM are genetic in etiology, one must not overlook acquired etiologies that can be treated to prevent disease progression. Further studies would be beneficial to elucidate the relationship between hypothyroidism and HCM in a pediatric population.
