Hereditary multiple exostoses: A case report and literature review

Abstract

Osteochondroma is the most common bone tumor representing 20%-50% of all benign bone tumors and 10%-15% of all bone tumors. Osteochondroma has similar radiological appearance in both solitary and multiple forms; the latter is an autosomal dominant disorder termed hereditary multiple exostoses. Associated complications of osteochondroma include deformity, fracture, neurovascular compromise, bursa formation, and malignant transformation. Measurement of the cartilage cap thickness is an important index suggesting secondary malignancy of osteochondroma. The upper limit of cap thickness after skeletal maturation is 1.5 cm which can be reliably measured on ultrasound or magnetic resonance imaging. Hereditary multiple exostoses are linked to the mutations of different exostoses genes located on chromosome 8, 11, and 19. We reported cases of two siblings presented with multiple osteochondromas managed by surgical excision. We evaluated their clinical and radiological presentation, genetic correlations and compared with the literature.

Keywords: Hereditary multiple exostoses; osteochondroma.

Figure 1.

Images of the 13-year-old patient (a), 8-year-old patient (b), their father (c), and grandmother (d) showing multiple palpable masses of their limbs and chest wall.

Figure 2.

Radiographies of the 13-year-old patient showing multiple sessile or pedunculated bony structure arising from the right proximal humeral metaphysis and left proximal humeral shaft (a), bilateral distal femoral metaphysis (b), bilateral proximal and distal tibial and fibular metaphysis (b and d), bilateral distal radial and ulnar metaphysis (d), consisted with multiple osteochondromas. Both distal tibiofibular joints were deformed. The right proximal humeral metaphyseal osteochondroma showed rings and arcs calcification, typical for osteochondroma.

Figure 3.

Contrast-enhanced MRI of the right humeral mass (blue arrow) of the 13-year-old male patient showed hypointensity on axial T1w image (a), hyperintensity on coronal PD FATSAT image (b) with a cartilage cap of 2–3 mm thickness (red arrow), well-delineated margin, heterogeneous enhancement after intravenous injection of gadolinium on axial and coronal post-contrast T1 FATSAT images (c and d).

Figure 4.

Radiographies of the 8-year-old patient showing multiple sessile or pedunculated bony structure arising from bilateral proximal humeral metaphysis, right ribs and right scapula (a), bilateral distal femoral metaphysis (c), bilateral proximal and distal tibial and fibular metaphysis (c and d), bilateral third proximal phalanges (b), bilateral distal radial and ulnar metaphysis (b), consisted with multiple osteochondromas. The left proximal humeral osteochondroma and right distal ulnar osteochondroma showed rings and arcs calcification. Fracture and deformity of right distal radius and deformity of the left distal fibula due to mass effect (red arrow).

Figure 5.

Contrast-enhanced MRI of the left humeral mass (blue arrow) of the 8-year-old male patient showed hypointensity on coronal T1w image (a), hyperintensity on axial PD FATSAT image (b) with a cartilage cap of 2–3 mm thickness (red arrow), clear margin without indistinction, heterogeneous enhancement after intravenous injection of gadolinium on axial and sagittal post-contrast T1 FATSAT images (c and d).

Figure 6.

Resected left humeral mass of the 8-year-old male patient in full observation (a, b, c) and cut in half (d). Macroscopic evaluation showed cauliflower-like calcification with a very thin cartilage cap.

Figure 7.

Microscopic evaluation of the resected humeral mass of the 8-year-old male patient. Histopathology showed the outer perichondrium (Star, a, H.&E ×200), the cartilage cap of 2 mm with superficial chondrocytes clustered (Star, b, H&E ×40), and the bony stalk with endochondral ossification at the base (Star, c, H&E ×400).

Figure 8.

Three-generation pedigree of our patients (red circles) with members diagnosed with HME marked by black square or circle.