A Fishy-Looking Bruise

An 8-year-old girl is experiencing mysterious bruising on her left shoulder. A thorough H&P reveals nothing remarkable, so you head to the computer…

It’s a weeknight in the Pediatric ED and business has been steady. Lots of respiratory viruses, a few broken bones, nothing too interesting or unusual. Then the nurses put a new patient in bed 1 with a chief complaint of “bruising.” You send in a resident who has a reputation for being thorough. She comes out a while later and doesn’t disappoint you – she’s asked them everything.  The child is an eight-year-old girl with bruising that the parents noted on her left shoulder yesterday. She didn’t give them any explanation for it, but these things happen to kids and her folks weren’t too concerned until they noticed some bruising starting on her right shoulder today. She’s had a few nosebleeds over the past few weeks but no other bleeding or bruising. She had a diarrheal illness two weeks ago, but no other recent illness. She has no fever, no night sweats, and no weight loss. Basically, she’s been just fine.

Her family doesn’t believe in immunizations, and she’s never had any. They do believe in supplements and she’s taking fish oil to “make her smart.” She got Nix about a month ago for head lice. The rest of her past history is unremarkable. Oh, and she’s a third grader in public school.


Her vital signs are normal for her age. She doesn’t look ill. Her color is good but she has unusually large, almost linear bruises on the lateral aspects of both shoulders. She has no bruising anywhere else on her body, and no petechiae. She has no adenopathy or hepatosplenomegaly. In fact, she is the picture of normal and abundant health except for the bruises.

Man, those bruises look odd – they’re so linear, almost like a friction burn. You take her aside and ask her, without her parents being present, if anyone has hurt her and she denies it. You ask the parents if they can think of any unusual rubbing of her shoulders but they draw a blank. You decide to order some blood work. As you wait for the results, you notice that there are no petechiae developing where the tourniquet was applied. Also, she begins to develop a new bruise on her right shoulder that looks like the others. So much for some occult trauma.

Her labs come back and they are completely normal. Normal CBC, normal platelets, normal coags, normal everything. This sure doesn’t looks like a hemotologic disorder. The only thing really different about this child is her dietary supplement. Can fish oil be causing this?


You look it up online and hit pay dirt: “Don’t take fish oil if you’re on aspirin.” “Don’t take fish oil if you’re on blood thinners.” The warnings are all over the place. As you read further you find articles in the pharmaceutical literature which describe bruising and nosebleeds – exactly what your patient has.

Fish oil appears to increase bleeding time and decrease platelet aggregation. It increases the rate of fibrinolysis (the process by which clots break down). It may even reduce the level of von Willebrand factor in the blood.

Fortunately, these abnormalities all resolve when the patient reduces or stops taking fish oil. You share your findings with the child’s parents and they agree to stop giving her fish oil and see if the bruising resolves.

Fish oil supplements can have other side effects. The most common are a fishy odor on the breath, stomach upset, and greasy stools. Fish oil can raise LDL cholesterol. Large doses can produce weight gain, and decrease the absorption of the fat soluble vitamins A, D, E, and K. Patients with diabetes may have an increase in blood sugar if they take fish oil. And impurities in some fish oil supplements have been associated with heavy metal exposure, such as mercury.


You knew there was something fishy about those bruises.

Amy Levine, MD, is an associate professor of pediatric EM at UNC Chapel Hill


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