joint stiffness leads to the diagnosis of a rare disease

Introduction: a 6-year-old boy was referred to our hospital because of the stiffness of both knees, which had commenced two years ago and gradually progressed to both hips, ankles, elbows, fingers, and toes. he occasionally had arthralgia with no complaint of joint swelling. he had a long face, a prominent forehead and chin, and a short neck. there was a limitation in the range of motion in all appendicular joints with stiffness and deformity. case presentation: skeletal survey images revealed central beaking and a bullet shape appearance in the cervical and lumbar vertebra, tapering of iliac wings, deformity of the femoral head, and short sacral length. a +3 glycosaminoglycan (gag) excretion was detected in the urine test, but genetic analysis revealed mucolipidosis type iii. conclusions: the diagnosis of metabolic diseases should be considered whenever there is joint stiffness without any evidence of inflammation. mucopolysaccharidoses and mucolipidoses are progressive storage disorders with many clinical and radiological characteristics.