| Answer to PhotoQuiz 55 |
| Multiple Exostoses (OMIM # 133700 & 133701) |
| Multiple exostoses, also known as hereditary multiple exostoses or hereditary multiple osteochondromas, is an autosomal dominant disorder characterized by the growth of multiple osteochondromas from the metaphyses and less commonly the diaphyses of long bones. The ribs, pelvis and/or scapulae may also be involved. It may be associated with short stature, Madelung-like deformity of the forearm, and peripheral nerve compression. There is around 2 – 5% risk of malignant transformation of the lesions to chondrosarcomas. It is caused by heterozygous pathogenic variant in the EXT1 (OMIM *608177; multiple exostoses type I) or EXT2 (OMIM *608210; multiple exostoses type II). Multiple exostoses type III (OMIM % 600209) has been mapped to a locus on chromosome 19. |
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| Correct responses were given by: |
| 1. Dr Ravneet Kaur, All India Institute of Medical Sciences, New Delhi, India 2. Dr Sreelata Nair, Lifeline Super Speciality Hospital, Adoor, Kerala, India 3. Dr Kanika Singh, Maulana Azad Medical College, New Delhi, India 4. Dr Surya G Krishnan, Indira Gandhi Institute of Child Health, Bangalore, India 5. Dr Sangeeta Khatter, Jindal IVF Hospital, Chandigarh, India |