Dysplasia Epiphysealis Hemimelica

Clinical History

A 3-year-old boy presented to orthopaedics outpatient clinic with a history of painless bony swelling limited to medial side left ankle joint for the past few months.

Imaging Findings

A 3-year-old boy presented to orthopaedics outpatient clinic with a history of painless bony swelling limited to medial side left ankle joint for the past few months. On examination a painless hard mass was palpable at the medial aspect of left ankle with good range of ankle movements. There was no leg length discrepancy. The family history was unremarkable. Plain radiographs suggested an osteochrondroma following which an excision biopsy done which confirmed the same. The swelling has recurred rapidly in about 12 month’s time following the excision. At surgery for re-excision, it involved the growth plate on the tibial side and also the dome of the talus. Further plain radiographs showed a classic radiographic appearance of asymmetric medial epiphyseal overgrowth with a well-structured accessory epiphyseal ossification centre over the medial talar dome separate from the genuine epiphysis. A radiological diagnosis of Dysplasia Epiphysealis Hemimelica was supported by histological appearance of osteochondroma. The swelling recurred shortly following re-excision after which it was decided manage the patient conservatively with no further surgical intervention.

Discussion

Dysplasia Epiphysealis Hemimelica (DEH) is characterised by asymmetrical abnormal cartilage proliferation and associated endochondral ossification (osteocartilaginous growth) in an epiphysis or in a tarsal, carpal or flat bone. Mouchet and Belot first described it in 1926^1,8. In the English literature it was first reported by Trevor, who called it tarsoepiphyseal aclasis or Trevors Disease^2,6. Because of the predisposition to either the medial or lateral half of a single limb, Fairbank proposed the name Dysplasia Epiphysealis Hemimelica in 1956 which is the most commonly used term^{4, 5, 8}. The aetiology is unknown, and DEH is extremely rare with a prevalence of one per million. No hereditary or familial factor has been demonstrated. M: F ratio of 3:1. DEH predominantly affects the lower extremity (usually a single extremity), with very rare upper extremity involvement of humerus, ulna, and scapula^1,7. DEH is usually restricted to the medial or lateral side of the limb (hemimelic). The medial side affected twice as frequently as the lateral. Azouz et al subdivided this congenital hamartomatous disorder in to three different types^{1, 2, 4}: 1) the classical form, characterised by hemimelic distribution or epiphyseal osteochondromas usually affecting a single lower extremity (monomelic) and commonly seen in the knee and ankle. This accounts for more than two-thirds of cases, 2) the generalised or severe form, with involvement of the entire extremity most commonly the lower extremity; and 3) the localized form, with monoarticular localisation most commonly occurring in ankle or hind foot. Radiology: Classic radiographic appearance of asymmetric epiphyseal overgrowth with multiple ossific centres. Irregular multicentric, coalescent radio-opacities incorporated into epiphyseal ossification, or a well-structured accessory epiphyseal ossification centre merging with or being separated from the genuine epiphysis. Physis may close prematurely resulting in limb deformity and limb length discrepancy. The articular surface is often irregular and, combined with the angular deformity. This frequently results in premature secondary osteoarthritis^{1, 5.6,8}. Under-tubulation of bone may occur due to secondary involvement of metaphysis^1. CT scanning has been used to more accurately define the anatomy of the epiphysis and joints. However, CT demonstration of soft tissues and cartilage is limited. Also, the relationship in planes other than axial is better evaluated with MR imaging^{1, 8}. MRI depicts the un-ossified cartilaginous mass in great detail, as well as the status of the articular cartilage, and helps to differentiate the abnormal epiphyseal growth from the main epiphysis^{1, 3}. The lesion and involved epiphyseal cartilage have similar signal intensity, with intermediate signal intensity on T1-weighted and high signal intensity on T2-weighted MR images. Areas of low signal intensity on T1- and T2-weighted images indicate areas of calcification or ossification that increase as the lesion and patient's skeletal maturity progresses^{1, 2, 3}. Radiological features are diagnostic & biopsy is usually not necessary. However, a skeletal survey should be performed to exclude additional areas of involvement, particularly of the lower extremities¹. Surveillance and clinical assessment are usually continued until the patient reaches skeletal maturity to assess the progression of the disease.

Differential Diagnosis List

Final Diagnosis

Dysplasia Epiphysealis Hemimelica (DEH)

URL:	https://www.eurorad.org/case/2334
DOI:	10.1594/EURORAD/CASE.2334
ISSN:	1563-4086