Hereditary multiple exostoses is characterised by growths of multiple benign bone tumours, called osteochondromas, which are covered by cartilage and grow outward from the metaphyses of long bones. Osteochondromas can be associated with reduced skeletal growth, short stature, premature osteoarthrosis, and compression of peripheral nerves. The median age of diagnosis is three years old; nearly all affected individuals are diagnosed by twelve years of age and males tend to be more severely affected than females.  The risk for malignant degeneration to osteochondrosarcoma increases with age, although the lifetime risk of malignant tumour development is low (~1%).

Autosomal dominant variants in the EXT1 and EXT2 genes cause multiple exostoses (Hecht et al. 1997 Am J Hum Genet 60(1),80-86), Wuyts et al. 2000 Hum Mutat 15(3), 220-227). A combination of sequencing and dosage analysis is reported to detect a variant in 70-95% of affected individuals (Jennes et al. 2009 Hum Mutat 30(12),1620-1627).

The laboratory participates in the European Molecular Genetics Quality Network (EMQN) sequencing scheme.