The symptoms are different for different disorders. Some of them cause bone growth problems. People with bone growth disorders may have brittle bones or bones that are too long or too short. Some cause people to be unusually tall (Marfan syndrome) or short (chondrodysplasias, osteogenesis imperfecta), or to have head and facial structure malformations (Apert syndrome, Pfeiffer syndrome). In others, joints may be stiff or immobile (fibrodysplasia ossificans progressiva or FOP).