Bone pain and malignancy red flags — branching viva

Opening question

A six-year-old boy has three weeks of deep right thigh pain that now wakes him from sleep, he is pale and tired, and his mother has noticed a few bruises; examination shows non-articular tenderness over the distal femur. What is the clinical task at this first visit, what is the single most reliable cardinal red flag, and what two tests do you order today? [1] [2]

Branch 1 — the leukaemia-versus-arthritis trap

A four-year-old girl is referred with a label of monoarticular juvenile idiopathic arthritis of the knee but has no morning stiffness, deep thigh rather than joint pain, pallor, lymphadenopathy, and a platelet count of 62 times ten to the ninth per litre. Which diagnosis does this pattern favour, what are the four discriminating features from the Jones study, and why is a low platelet count particularly discriminating against juvenile idiopathic arthritis? [2]

Branch 2 — the radiographic signatures

The same registrar now describes three radiographs: one with metaphyseal lucent bands, one with a mixed lytic and sclerotic metaphyseal lesion and a Codman triangle, and one with a permeative diaphyseal lesion and an onion-skin periosteal reaction. Name each diagnosis, relate each radiographic feature to the tumour biology, and state which one is the great mimic of osteomyelitis. [3] [9]

Branch 3 — the never-biopsy rule

A fifteen-year-old boy with a destructive distal femoral lesion and a firm mass has been booked for an incisional biopsy at a peripheral hospital tomorrow. What is the correct principle governing the biopsy of a suspected primary bone tumour, what harm does it prevent, and how do you explain the urgency to the surgical team? [8]

Closing — the emergency and the safety-net

In one sentence, what is the diagnosis you must assume for any child with back pain and a neurological deficit, what is the immediate management, and why must every child sent home with a benign label still carry a safety-net and a re-review? [9] [1]