Genetic disorders of the osseous skeleton constitute a challenging area of differential diagnosis. Three patients, 2 girls and 1 boy, were referred to our pediatric rheumatology clinic because of progressive stiffness of their hands and flexion contractures of fingers, accompanied by additional musculoskeletal changes. One of the girls had been diagnosed in early childhood as having juvenile rheumatoid arthritis, the other was suspected to have scleroderma, and the boy had been labelled with "Hurler's syndrome." On evaluation, all 3 patients had the clinical and roentgenographic features of mucolipidosis III; the diagnosis of mucolipidosis III was confirmed by enzymatic assays. We call for an awareness of pediatricians, rheumatologists and orthopedic surgeons to the "rheumatological" presentation of mucolipidosis III. The establishment of a precise diagnosis will lead to adequate management and will allow appropriate genetic counseling.