Osteoid Osteoma Presenting With Unilateral Leg Wasting

Osteoid osteomas are uncommon in children and are typically seen in the second and third decades of life [1]. We present a toddler presenting with unilateral leg wasting who was eventually found to have an osteoid osteoma.

A previously well 3-year-old boy was referred to the paediatric clinic at a regional hospital due to an intermittent limp which his parents reported had been present since starting to walk at 1 year. There was no history of trauma, and he was systemically well. On examination, he could walk and run with no convincing gait disturbance. His right calf appeared wasted and measured 1 cm thinner than the left. There was no leg length discrepancy or joint irritability. He had normal deep tendon reflexes (DTR) and down-going plantars. Our initial differential diagnosis included hip or spinal pathology and peripheral neuropathy causing unilateral leg atrophy. X-ray revealed a lucent lesion in the right distal tibia with periosteal reaction (Figure 1), which we suspected could be chronic osteomyelitis or Langerhans cell histiocytosis. Blood tests revealed unremarkable inflammatory markers and negative blood culture. CT showed a 9 mm circumscribed lytic lesion (nidus) within the lateral cortex of the right distal tibia (Figure 1).

He was discussed with the orthopaedics team at a tertiary paediatric centre and transferred with the presumptive diagnosis of chronic osteomyelitis on IV cefazolin. MRI showed a cortical-based lesion with extensive marrow inflammation and surrounding soft tissue inflammatory changes. Fluoroscopic guided debridement and biopsy were performed. Histology confirmed an osteoblastic lesion favouring the diagnosis of an osteoid osteoma. He was discharged on oral antibiotics, managed in a Controlled Ankle Motion (CAM) boot to mitigate the risk of pathological fracture, and had complete resolution of symptoms on subsequent follow-up.

Osteoid osteomas account for 10% of benign bone tumours [2], commonly affecting long bones such as the femur or tibia [1, 3] It is rare in children < 3 years, and non-specific symptoms tend to delay diagnosis [1, 3]. Presenting complaints include gait disturbance and nocturnal pain that responds to simple analgesia [1]. Hsich et al. [3] reported two patients with lower limb osteoid osteoma presenting with focal neurologic signs including atrophy, weakness, and reduced DTR due to affected limb disuse. CT is most reliable in showing the focal lucent nidus and surrounding reactive sclerosis, which may not be seen on x-ray or MRI [1, 2]. Osteoid osteomas have been reported to spontaneously resolve; however, treatment traditionally involves surgical resection or radiofrequency ablation [1, 2, 4].

Our case highlights osteoid osteoma as a rare but treatable differential in toddlers presenting with chronic gait disturbance and muscle wasting.

The authors declare no conflicts of interest.