Mucopolysaccharidosis type 4 (Morquio syndrome): A case report

INTRODUCTION: Mucopolysaccharidosis (MPS) IVA (Morquio syndrome) is a rare lysosomal storage disease, that is caused by a deficiency in the enzyme N-acetylgalactosamine-6-sulfatase (GALNS) due to an autosomal recessive mutation in the GALNS gene. Herein, we present a MPS IVA case without regular follow-up, whose enzyme replacement was planned to start at age 30 for the first time, so as to attract attention to this rare disease. CLINICAL CASE: A 30-year-old female patient diagnosed with MPS IVA, that was evaluated due to corneal clouding referred to the Marmara University endocrinology outpatient clinic for enzyme replacement. On admission, she complains of impaired vision, hearing loss, hypoglycemic symptoms and numbness of hands and feet. While she was normal for about 2 years after birth, she was noticed for delays in crawling and walking from 2–3 year of age. However, she had definitive diagnosis of MPS-IVA at the age of 9 years, with low enzymatic analysis and genetic mutation in the GALNS gene located on chromosome 16q24.3. She operated on for bilateral glaucoma and cerebellar mass when she was 17. Her parents were third degree consanguineous, and she had one healthy younger brother. On physical examination, blood pressure: 99/67 mmHg, pulse: 72/min, temperature: 36°C, SpO2:99. She was in a wheelchair. Her height was 92 cm, weight was 30 kg, BMI: 25.6 kg/m2. Disproportionate short stature, coarse facial features, hypertelorism, genu valgum, pectus carinatum, kyphoscoliosis, were detected. Her neuromotor development was normal. Laboratory findings were unremarkable except for vitamin D hypovitaminosis. Radiographic findings were dysostosis multiplex, include abnormally shaped vertebral bodies with anterior beaking, posterior scalloping, platyspondyly and dens hypoplasia, thoracolumbar kyphosis, short, broad metacarpals, acetabular dysplasia, genu valgum, pectus carinatum, paddle-shaped ribs and short, and thick clavicles (Fig 1). Bone densitometry results were in osteoporotic range BMD at the femoral neck was 0.491 g/cm2, Z score was -2.8 and at the lumbar spine was 0.707 g/cm2, Z score was -3.6. She continued the 6-min walk test with the help of a walker and knee pad for 2.37 minutes and walked 3.4 meters. Echocardiography demonstrated that ejection fraction was 65%, normal left ventricular systolic function, no ventricular segmental wall motion defect, aortic 3 cusps, mild to moderate aortic valvular regurgitation, mild mitral valvular regurgitation. Pectus carinatum was detected on thorax CT imaging, whereas a restrictive disease pattern was not observed in PFT and DLCO. Bilateral severe mixed hearing loss was detected. Recombinant human GALNS (elosulfase alfa), 2.0 mg/kg/week, was planned to administer IV in 4 hr. [Figure: see text] CONCLUSION: Because of the progressive nature of MPS- IVA, early diagnosis and early initiation of enzyme replacement therapy are critical to prevent cumulative systemic manifestations of the patient, especially the skeletal system.