ESPE Abstracts

Background: Hereditary multiple exostoses (HME) is an autosomal dominant heritable disorder characterized by exostoses located mainly in the long bones of extremities. HME is caused by mutations in two genes: EXT1, EXT2.

Objective and hypotheses: Growth hormone (GH) deficiency is very rare in children with HME and GH replacement therapy has not been well described.

Method: A 12.5 years old girl was referred to our Department because of short stature (132 cm, −2.8 SDS). Her weight was 24 kgr (BMI 13.77, −2.53 SDS), she had reduced growth rate (2.3 cm/year) and was on pre-pubertal maturation stage. Physical examination was normal. Her father had multiple exostoses on scapulae and long bones and was under orthopedic follow up. Hypothyroidism, chronic diseases, malabsorption and skeletal dwarfism were excluded. GH deficiency was diagnosed by two stimulation tests: insulin (GH peak: 5.36 ng/ml) and L-dopa administration (GH peak: 7.35 ng/ml) and confirmed by low IGF-I values (214 ng/ml). Bone age was delayed (10.5 years) with exostoses on third metacarpal, distal radius bone and middle phalanx of third finger. X-rays showed exostoses on scapulae, knees and distal femurs. She was referred to orthopedics who confirmed the diagnosis of HME.

Results: GH replacement therapy (0.025 mg/Kg per day) showed good response on linear growth: 6.1 cm (1.4 SDS) during the first year and 4.2 cm (3.0 SDS) the second year of therapy. Her mother was negative for exostoses while her sister (10 years old) showed short stature (141.8 cm, −2,5 SDS), reduced growth rate 2.8 cm/year and exostoses (right scapulae and knees) at x-ray examination. GH deficiency was diagnosed by insulin (GH peak 2.11 ng/ml), L-dopa stimulation tests (GH peak 2.35 ng/ml) and low IGF-1 (207 ng/ml).GH replacement treatment (0.025 mg/kg per d) showed moderate response: 5.5 cm/year (−0.8 SDS) the first year and 3.8 cm/year (−0.8 SDS) the second.

Conclusion: GH deficiency has rarely been found in HME patients. GH replacement treatment seems to improve their stature, however close follow up of exostoses is mandatory.