What are the signs and symptoms of Metachondromatosis? Metachondromatosis (MC) is characterized by the presence of both multiple enchondromas and osteochondromas. The features of the condition generally become apparent in the first decade of life. Enchondromas are benign (noncancerous) tumors that appear on the inside of the bone. Those that are associated MC typically involve the iliac crests (part of the pelvis) and metaphyses of long bones, particularly the proximal femur (portion of the thigh bone closer to the trunk). These tumors are usually painless, but when they appear in the hands or feet, or in multiple lesions (as is typical in MC), they can deform the bone. Osteochondromas are also benign tumors. These form on the surface of the bone near the growth plates (areas of developing cartilage tissue near the ends of long bones in children) and are made up of both bone and cartilage. Osteochondromas may grow as the affected child grows, and stop growing when the child reaches skeletal maturity. They have a tendency to regress or disappear after the first or second decade of life. Those that are associated with MC most frequently occur in the small bones of the hands and feet, predominantly in digits and toes. The characteristic location and orientation of these in individuals with MC (as well as lack of bone shortening and short stature) are what generally differentiate MC from hereditary multiple osteochondromas (HMO), a disorder with overlapping features. The osteochondromas of MC point toward the joint to which they are adjacent (whereas those of HMO point away). Osteochondromas often cause painless bumps, but pain or other discomfort may occur if the tumors put pressure on soft tissues, nerves, or blood vessels. The Human Phenotype Ontology provides the following list of signs and symptoms for Metachondromatosis. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Abnormality of epiphysis morphology 90% Abnormality of pelvic girdle bone morphology 90% Abnormality of the metaphyses 90% Aseptic necrosis 90% Bone pain 90% Chondrocalcinosis 90% Cranial nerve paralysis 90% Exostoses 90% Multiple enchondromatosis 90% Abnormal joint morphology - Autosomal dominant inheritance - Bowing of the long bones - Multiple digital exostoses - The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.