An unusual finger injury

A 39 year old female farmer with no medical history presented to the emergency department with a painless swelling over her right index finger. The problem started two weeks earlier after she had been bitten by a lamb. After the injury the finger appeared “bruised.” This bruising continued and a swelling gradually developed. She reported no pain, changes in sensation, or reduced range of movement . On clinical examination she was afebrile and haemodynamically stable. Her right index finger exhibited a full range of movement and was neurovascularly intact. The finger was not tender on direct palpation and it seemed to be the same temperature as her other fingers. The finger had a laceration on the radial aspect proximal to the nail fold, with a demarcated and raised area of reddish-blue discoloration measuring about 2 cm × 1.5 cm (fig 1⇓). There was no palpable lymphadenopathy within the axilla. Fig 1  Injured right index finger 1. What are the differential diagnoses? 2. What is the most likely diagnosis? 3. What investigations might be ordered? 4. How is this condition managed? ### 1. What are the differential diagnoses? #### Short answer Bruising (eg post-trauma), paronychia, herpetic whitlow, orf virus infection, Milker’s nodule, pyogenic granuloma, keratoacanthoma, and osteomyelitis. #### Discussion Bruising is a common soft tissue injury (fig 2⇓). It is often secondary to trauma and is characterised by a bluish or purple coloured patch as a result of underlying capillary damage. Bruising is typically painful initially and usually resolves within a few weeks, fading to a greenish-yellow colour before the skin finally returns to normal. Fig 2  Bruising to the finger. Credit: Dr P Marazzi/Science Photo Library.SPL In paronychia (fig 3⇓) the infection generally starts in the paronychium at the side of the nail, with local redness, swelling, and pain. The lesion is tender …