Teriparatide in Two Patients With Mucopolysaccharidosis Type <scp>IVB</scp>

Mucopolysaccharidosis Type IV is a multisystem lysosomal storage disease characterized by severe skeletal dysplasia resulting from impaired degradation of the glycosaminoglycans keratan sulfate and chondroitin-6-sulfate. The condition is classified into Types A and B based on the underlying enzyme deficiency. Low bone mineral density (BMD) is a feature of the skeletal phenotype, contributing to increased fracture risk. Extraskeletal manifestations include, among others, cardiovascular disease due to valvular stenosis and regurgitation, myocardial remodeling, coronary artery disease, and vascular stiffness, all associated with glycosaminoglycan accumulation. We report two adult patients with mucopolysaccharidosis Type IVB treated with the osteoanabolic agent teriparatide for an apparently low BMD. The first patient presented with a non-healing femoral fracture requiring BMD improvement prior to surgical fixation. This patient was treated with teriparatide for 2 years, which resulted in significant BMD gain, enabling successful surgical fixation. The second patient received teriparatide for only 6 months and showed stable BMD. Notably, both patients developed serious cardiac problems during teriparatide treatment: the first patient experienced rapidly progressive aortic stenosis, while the second patient developed dyspnea and polyuria due to worsening dynamic left ventricular outflow tract obstruction, which had previously been asymptomatic. Both patients required invasive cardiac interventions, which carry high risk in mucopolysaccharidosis due to unique anatomical and anesthetic challenges. The temporal association between teriparatide treatment and the onset of cardiac problems in both patients is noteworthy and raises the possibility of a treatment-related effect. Therefore, we recommend cautious use of teriparatide in patients with mucopolysaccharidosis Type IV.