Can you get this one?

Srijita Ghosh DNB,MNAMS,FRCR(London)
Senior Consultant Radiologist, Apollo Multispecialty Hospitals, Kolkata

10-year-old boy with bulbous soft tissue swelling in both thumbs which was gradually increasing in size over 6 months. He had a history of recurrent knee joint swelling over the last few years which settled down spontaneously. He denied any history of trauma.

Question: Identify the underlying disease

Answer: Note the expansile lytic lesion in proximal phalanx of the thumb involving proximal phalanx, initially well defined, which progressively showed erosive changes and periosteal reaction. Interestingly the lesion started to reduce in size and vanish. This boy represents juvenile hemophylic pseudotumorous lesions in both thumbs. Unlike adult hemophilic pseudotumours that affect large flat bones, juvenile hemophilic pseudotumours are known to affect small bones of the hand as in this case.