Left-sided valvular heart disease and retinopathy in a 38-year-old woman with attenuated mucopolysaccharidosis: a case report

Mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage disorders caused by deficient levels and/or activity of glycosaminoglycan (GAG)-degradative enzymes. MPS are characterized by accumulation of the mucopolysaccharides heparan sulfate, dermatan sulfate, keratan sulfate, or chondroitin sulfate in tissues. We report the case of a 38-year-old woman with a history of joint restriction and retinitis pigmentosa who developed bivalvular heart failure requiring surgery. It was not until pathological examination of surgically excised valvular tissue that a diagnosis of MPS I was made. Her musculoskeletal and ophthalmologic symptoms, when placed in the context of MPS I, painted the diagnostic picture of a genetic syndrome that was overlooked until a diagnosis was made in late middle age. A 38-year-old woman with heart failure had heart valve surgery. Examining her cardiac valve tissue under the microscope suggested a metabolic disorder called mucopolysaccharidosis type I (MPS I). MPS I is due to defective breakdown of sugar molecules (called glycosaminoglycans or GAGs for short) in the body which then can accumulate, causing dysfunction. Our patient had short stature, a curved spine, stiff joints, and a degenerative eye disease called retinitis pigmentosa, all of which were due to her undiagnosed MPS I. Most patients with MPS I are discovered on newborn screening when they are babies, or at very young ages due to severe symptoms related to the disease. Our patient had a form of MPS I that was less severe, and the first symptom she received medical care for was her eye symptoms. A diagnosis of MPS I made in middle adulthood is unusual for MPS I, and so is an important learning case for providers as there were clues hidden in her medical history that suggested a genetic or inherited syndrome. Our genetics specialists were able to make a definitive diagnosis of MPS I and begin treatment with enzyme replacement therapy, as well as provide information for the patient about her risk of passing this disease on to children.