Table 1 Common presenting/early symptoms in patients with attenuated MPS I [24, 51]

• Growth delay (normal birth weight, but growth failure or short stature)

• Joint contractures (primarily in hands/claw hand deformity), joint pain and stiffness, restricted mobility

• Carpal tunnel syndrome (trigger digits)

• Recurrent hernias (umbilical and/or inguinal)

• Corneal clouding

• Hepatosplenomegaly

• Skeletal abnormalities/dysostosis multiplex (e.g., kyphosis, scoliosis, hip dysplasia, flattened vertebral bodies, oar-shaped ribs, short thickened clavicles, bullet-shaped phalanges, dysplastic femoral heads, flattened acetabula, coxa valga and genu valgum deformities)

• Ear/nose/throat symptoms (recurrent ear infections, noisy breathing, sleep apnea, enlarged tongue, hearing loss)

• Heart murmur (valve abnormalities)

• Surgical history of multiple hernia repairs, PE tubes, tonsillectomy, adenoidectomy