Teaching Case

An 8-year-old male patient presented with left ankle pain and limited motion slowly progressed within the last two years. No history of trauma, infection, malignancy, or operation.

Dedicated computed tomography (CT) of the left ankle joint revealed irregular boney outgrowth is seen originating by a small pedicle from the postero-lateral surface of the distal tibial epiphysis. It shows cortex and medullary continuity with the tibial epiphysis.

Lateral bowing and deformity of the distal fibula are noted as compensatory to the tibial boney outgrowth.

Another similar epiphyseal boney outgrowth is seen originating from the talar dome, it also shows continuity with the talar bone. It is associated with the subsequent widening of the tibiotalar joint.

Multiple ossified intraarticular loose bodies are noted secondary to fragmentation of the previously described boney outgrowth.

Magnetic resonance imaging (MRI) of the left ankle joint confirmed the cortical and medullary continuity of both the tibial and talar boney outgrowth.

The CT and MRI appearance of the lesions as well as the patient’s age were typical for the classic form of dysplasia epiphysealis hemimelica (DEH) (Trevor’s disease) involving the distal tibial epiphysis and the talar dome.

Dysplasia epiphysealis hemimelica (DEH) is a rare non-hereditary disorder affecting the epiphysis at one side. The clinical features of the disease are not specific and it may overlap with traumatic injuries, infections, or other tumors. The lesions show no malignant potentials nor hereditary transmission [1].

Early reports suggested that the condition affects the lower limbs only. However, later on, many reports indicated upper limb involvement as well as more generalized distribution [2].

The most commonly affected lower limb joint is the ankle, followed by the knee and the hip.  However, in the upper limb the most commonly affected joint is the wrist, followed by the elbow and the shoulder. Azouz et al. have classified lesions into:

• Classic form: involving more than one bone within one lower limb.
• Localized form: involving a single bone either unilateral or bilateral.
• Generalized form: in which the whole limb is involved from pelvis to foot [3].

The diagnosis is usually made by the characteristic radiographic appearance. The typical involvement is characterized by epiphyseal cartilaginous overgrowth, that occurs asymmetrically and contains multiple ossific centers. There are different patterns of epiphyseal chondral ossification that can be stippled, irregular, or dense. The involved epiphysis is usually larger than normal and there is associated metaphyseal widening and remodelling [5].

When DEH is totally ossified, its histological appearance is indistinguishable from osteochondroma. So, the key to differential diagnosis is the lesion location and age of presentation. Osteochondroma mostly affects the metaphyseal region of the long bones, while DEH arises from epiphysis. Most patients are younger than 30 years at the time of diagnosis [4].

The treatment should be individualized according to the patient’s condition. Asymptomatic lesions should receive palliative treatment. However, if the lesions cause pain and deformity surgical treatment is recommended. It is of note that there can be recurrence after surgery if surgery is performed before the closure of the physis [4].

Written informed patient consent for publication has been obtained.