Clinical History
A 6-year-old boy presented with deformity of the right wrist.
Imaging Findings
Plain radiographs of right wrist were performed which demonstrated the presence of irregular ossified lesions continuous with the distal epiphysis of the radius, scaphoid, trapezium, and proximal epiphysis of the first metacarpal bone (see Fig. 1). In addition, global enlargement of the scaphoid and the trapezium was noted. The radiographic features were suggestive of dysplasia epiphysealis hemimelica (Trevor’s disease) that involved carpal bones and the epiphysis of the radius and of the first metacarpal bone, i.e. the classic form of Trevor’s disease.
Magnetic resonance (MR) of the right wrist confirmed the cortical and medullar continuity of the bone excrescences with the corresponding bones as well as its osseous and cartilaginous nature that therefore have a osteochondroma-like appearance (see Fig. 2). The association of the carpal masses to joint effusion is responsible for the mechanical burden that these deformities convey and that underlies the complaints.
The characteristic radiographic and MR findings as well as the age group were important to diagnose the classic form of dysplasia epiphysealis hemimelica in a rather unusual location, leading to prompt diagnosis and referral, and therefore avoidance of early joint degeneration.
Discussion
Dysplasia epiphysealis hemimelica (DEH) is a rare bone developmental dysplasia characterised by aberrant and asymmetric osteocartilaginous outgrowth from epiphyses, apophyses, tarsal, carpal, or rarely sesamoid bones, which is histologically indistinguishable from an ordinary osteochondroma. Historically, DEH had many names (tarsomegaly, tarsoepiphyseal aclasis, Trevor-Fairbank disease) denoting its clinical polymorphism.
DEH reported prevalence is 1 in 1 000 000 persons. DEH aetiology remains unknown, no pattern of heritage has been identified, possibly relating to an embriopathy.
DEH's age of presentation is 2-14 years and it is three times more common in boys. Initial complaints include unilateral, painless, asymmetric, firm swelling on one side of a joint, limitation of movement, and later pain, limb wasting, valgus or varus deformity, and sometimes limb length discrepancy.
The osteocartilaginous outgrowth is characteristically hemimelic and more commonly located in the medial aspect of the lower limb (distal femur>proximal tibia>talus>tarsal navicular>first cuneiform) and exceptionally in the upper limb and sesamoid bones.
DEH can be classified according to Azouz into localised (restricted to a single bone), classic (2/3 of cases), or generalised form. In the classic form more than one bone in a single extremity is involved as depicted in the case presented here. In the generalised or severe type the whole limb is involved.
Usually, the diagnosis is radiographic. Radiographs typically show asymmetric cartilaginous ossification centres with bony outgrowth, containing scattered stippled calcifications that may coalesce in a lobulated irregular mass, ossifiy, and become confluent with the underlying bone. There may be associated deformities as secondary widening of the metadiaphysis with undertubulation. A skeletal survey should be performed to exclude additional areas of involvement.
CT may be useful to prove lesion continuity with underlying cortex and bone marrow. MR complements the radiographic assessment, establishing the cartilaginous or osteocartilaginous nature of the lesion and its epiphyseal origin. Additionally, MR better depicts the exact location and extent of the lesion, joint involvement, and cleavage planes. Differential diagnoses include “traction” exostoses and other osteochondroma-like bone excrescences; solitary or multiple osteocartilagenous tumours (osteochondroma, multiple osteochondromas, metachondromatosis); and the rare chronic infantile neurologic, cutaneous, and articular (CINCA) syndrome.
Although malignant transformation has not been reported, DEH may cause considerable morbidity. Lesions may enlarge with skeletal growth, cause premature closure of the physis, joint deformity, and limb discrepancy. Articular surface irregularity may lead to early secondary osteoarthritis and is often associated with pain, deformity, or loss of normal mechanical function.
Surveillance is recommended until the patient reaches skeletal maturity, to assess disease progression. Surgical intervention is more frequently required for DEH than for solitary osteochondroma because the epiphyseal location makes it prone to be symptomatic more often. Of great practical importance is that DEH can go unrecognised for years and thus unfortunately adequate orthopaedic treatment is delayed and functional disability overcomes. Surgery should be performed at an early stage and aims to improve joint congruity, thus preventing or lessening subsequent secondary osteoarthritis and improving outcome. Excision, even incomplete resection, may result in reduction of symptoms, although the reported recurrence rate of deformity is high.
Differential Diagnosis List
Classic form of dysplasia epiphysealis hemimelica (Trevor’s disease)
Final Diagnosis
Classic form of dysplasia epiphysealis hemimelica (Trevor’s disease)
