8-year-old girl with a history of eating disorder, (height 1.29 m, 50th centile, weight 17.8 kg, 0.4th centile). Admitted for nasogastric feeding/psychiatry input. New right knee pain and difficulty walking. Iron deficiency anaemia on bloods. Pathological fracture/inflammatory changes needed exclusion. Later bleeding gums were demonstrated. Ascorbic acid/anti-psychotic medication was prescribed. Knee pain disappeared after 3 days with normal mobility.
Initial knee X-ray was unremarkable.
Subsequent right knee MRI showed marrow oedema around the proximal tibia / fibula metaphysis, reduced tibia growth plate thickness, significant periosteal thickening / reaction around the fibula and a joint effusion. Further significant soft tissue oedema around the focal bony changes was present mainly around the proximal fibula. The distal femoral growth plate was normal.
A repeat MRI 2 weeks later after ascorbic acid treatment showed complete disappearance of the marrow and soft tissue oedema around the proximal tibia and fibula metaphyses. The joint effusion had also disappeared. The minimal residual changes were subtle thickening around the proximal fibula and some minor narrowing of the lateral tibia growth plate.
Scurvy is usually a clinical diagnosis caused by vitamin C deficiency which is common in developing countries and often seen in developed countries where there is a history of an eating disorder.
Joint pains are often seen but rarely imaged when the history is not in doubt. The bleeding gums are the best clinical evidence to the diagnosis. However if history is confusing, knowledge of the differential diagnosis of the imaging findings is required.
Osteomyelitis is most common. Haematological neoplasia, Henoch Schonlein, sickle cell disease, vitamin deficiencies such as copper deficiency, rickets, arthritis, syphilis and Non-Accidental Injury (NAI) should be considered in the differential diagnosis. 
On detailed history taking after the first MRI, there was no history of trauma or infection in this patient. Biochemical markers of infection were normal and there was no convincing evidence of haematological disease. NAI was not suspected. A clinical diagnosis of scurvy was made with unfortunately no evidence of biochemical vitamin C levels.
The MRI changes of scurvy which have been described only a few times show areas of sub-periosteal fluid and epiphysis displacement. The marrow appearances probably represent small areas of haemorrhage or small infarcts. 
Historically X-rays were performed in well-established cases of scurvy. These have shown changes of osteopenia with sclerotic thick metaphyseal lines above a widened physis and small beak-like excrescences.  In our case the X-ray was performed after a short duration of symptoms and was therefore unremarkable.
The bleeding gums and knee pain stopped shortly after ascorbic acid treatment. The patient was discharged after gaining 3 kg with intensive community-based care / dietary input.
The MRIs in an interval of 2 weeks show how easily and quickly the highly visible changes can be reversed if the correct clinical diagnosis is made quickly.
Differential Diagnosis List