mercredi 2 septembre 2015

Bleeding Disorder? National Expert Discusses Questions Around Cambridge Baby’s Death

Bleeding Disorder? National Expert Discusses Questions Around Cambridge Baby’s Death

Aisling Brady McCarthy

Aisling Brady McCarthy watches as her attorney addresses the court during a status hearing at Middlesex Superior Court in Woburn in May. McCarthy, a nanny from Ireland, was accused of killing a 1-year-old Massachusetts girl in her care two years ago. (Charles Krupa/AP)

Aisling Brady McCarthy is back in her native Ireland now, after murder charges against her were dropped in the death of Rehma Sabir, a Cambridge infant in her care. But while the case is over, the mystery remains: How did Rehma die?

The Middlesex County district attorney’s office says a review of the case raised the question of whether 1-year-old Rehma had an undiagnosed blood disorder that could have caused her brain hemorrhage. A press release from the office cites these details from the medical examiner:

“Review of Rehma’s coagulation and hematology testing, her history of bruising, the NIH guidelines for diagnosis of von Willebrand disease, and literature on the subject suggest to me that Rehma’s low von Willebrand factor could have made her prone to easy bleeding with relatively minor trauma.

“Given these uncertainties, I am no longer convinced that the subdural hemorrhage in this case could only have been caused by abusive/inflicted head trauma, and I can no longer rule the manner of death as a homicide.  I believe that enough evidence has been presented to raise the possibility that the bleeding could have been related to an accidental injury in a child with a bleeding risk or possibly could have even been a result of an undefined natural disease.  As such I am amending the cause and manner of death to reflect this uncertainty.”

So, then, a bleeding disease might have caused a spontaneous hemorrhage? Or the combination of the disease and a minor head injury led to death? And if so, could it be that quite a few of the contested accusations of baby abuse in recent years could be thus explained away?

I turned to Dr. Shannon Carpenter, a bleeding disorders specialist who has done research and written American Academy of Pediatrics reports on checking children for bleeding disorders when there’s a question of abuse. She’s the chief of hematology at Children’s Mercy Hospital in Kansas City, Missouri, and the director of the Kansas City Regional Hemophilia Center.

Dr. Carpenter was not involved in the Cambridge case, but speaking generally she says that sadly, no, there’s no kinder explanation here: Abusive head trauma — a better term than “shaken baby syndrome” because abuse can involve more than shaking — is far more common than serious bleeding disorders, and even children with severe disorders are extremely unlikely to have fatal brain bleeds. Our conversation, lightly edited:

Dr. Carpenter, what are we to make of the medical examiner’s mention of Von Willebrand disease — a not-very-rare bleeding disorder — and the suggestion that death could have resulted from disease or “an accidental injury in a child with a bleeding risk”?

One thing I would say is, most patients with von Willebrand disease have a mild disorder, mostly manifested by nosebleeds, bruising, and gum bleeding, and do not seem to have an increased risk for intracranial hemorrhage. Research is ongoing in this area and I think there may be more information coming, but from a clinical perspective, when we see patients with the most common types of von Willebrand disease, we do not have a high concern for intracranial hemorrhage in those patients, certainly not spontaneously.

The most severe forms of von Willebrand disease occur in about 1 percent of people with von Willebrand disease, probably less than that. And even in the most severe forms, the risk of having a bleed inside of the head is probably less than 2 percent. So it’s a very rare event. This would be an unusual presentation for von Willebrand disease. I don’t know the specifics of this patient’s case, and I don’t know what her actual von Willebrand factor level was, but even if she was low enough to be diagnosed with the most common form of von Willebrand disease, this kind of bleeding would not be typical for that kind of diagnosis.

But, I suppose, possible?

While anything is possible, you have to look at what’s probable and what other patients have experienced. And patients with bleeding disorders are not immune to trauma, whether it’s inflicted or non-inflicted. I would say if a child came to me with type 1 von Willebrand disease, the most common type, the mild form of von Willebrand disease, with a typical toddler head bump that would not otherwise cause someone to seek medical care, I would not worry about intracranial hemorrhage in that patient.

And if a child had a more severe form of von Willebrand disease?

Then I might be concerned.

But if it were a severe form, wouldn’t it have likely shown up by 1 year of age?

Yes, the most severe forms of von Willebrand disease show up earlier because the children have more problems, they have more bleeding. So the individuals who have more severe forms, who have long nosebleeds even from a baby age, they’ll have gum bleeding as they cut their teeth, they’ll have bruising with normal handling and with normal moving around — even in those cases, usually trauma is required for bleeding, even if it’s mild trauma. And the rate of intracranial bleeding is still really low, surprisingly, even in severe forms.

The DA refers to additional materials — in the last couple of years, has there been any substantive change in how the field thinks about the likelihood of a bleeding disorder contributing to an appearance of abusive head trauma?

Not really. I think one of the things that the [American Academy of Pediatrics] technical and clinical reports did was identify that both need to be worked up, but it doesn’t change the natural history of the disease, just the fact that we now recognize that children should be evaluated for both. It doesn’t change the natural history of von Willebrand disease to say that someone may have it, it doesn’t make it a more severe disease. I’m not aware of any information suggesting that intracranial hemorrhage is more common in von Willebrand disease than previously known.

The research is ongoing and we may have more information forthcoming, but to date, no changes. There are always case reports that come out, but those aren’t really evidence, those are one patient, one association, and they can be interesting and lead us down a path where we can get more evidence but they don’t themselves provide good support for major changes in the medical understanding.

But might it be that in this pretty contentious field of abusive head trauma, that bleeding disorders could provide some sort of middle ground in which there could be some significant number of cases in which it looked like abuse but in fact might have been not so much a trauma as a bleeding disorder?

I don’t think it will be that many. I think there will be some cases — and it will be readily apparent because it will be the more severe bleeding disorders — where a child may have intracranial hemorrhage and we determine they have a very severe hemophilia or something of that nature. And it’s important that we look for those. But unfortunately, child abuse is more common than bleeding disorders. And while it is important to work up someone for a bleeding disorder, a bleeding disorder does not protect a child from abuse, so it’s important to make sure that’s not what’s happening.

We don’t want any child with a bleeding disorder to be taken from a home where they are safe and cared for. But by the same token, we don’t want to send a child back to a home where they’re at risk, because those children die. So you need to be very careful to be exact in this area.

What would you say have been the most significant scientific advances in this area recently?

I think the biggest advance is bringing the bleeding disorder work-up to the abuse population, and to try to say we should work both up simultaneously and with great care when there is a question. I think that’s the biggest advance, and there are quite a few more to come.

I also think we have a better understanding of what are the rates in the bleeding disorder population for intracranial hemorrhage, and it turns out they’re really rare — thank goodness, for our bleeding-disorder population.

So when you start to look at the numbers, you start to think: Well, this is really only a 1 in 500,000 chance that this child who has a bleeding disorder could walk in with an intracranial hemorrhage, or a 1 in a million chance. Then the chances of them actually having abusive head trauma start to go up.

And is it that order of magnitude? Maybe 1-in-a-million odds?

Yes, that’s all in the clinical report.

So then is there any takeaway that you would hope the public would draw from this case?

I think it’s a very difficult case; it’s very complicated and I don’t know all the details. I think one of the things I would take away is that people who have bleeding disorders are out there and so we should have an index of suspicion. So that should be something that should be worked up. But it doesn’t explain the cause for the vast majority of abusive head traumas.

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