15 March 2013

Capgras syndrome

It is striking when a very detailed and complex set of symptoms crop up in patients across history and around the world. One is Capgras syndrome, in which the patient believes that a loved one has been replaced by an identical-looking imposter.

A UC-San Diego neurologist, V.S. Ramachandran, hypothesized what might cause such a wild syndrome. One tiny part of the brain identifies faces, and another associates certain feelings with faces. In these patients, the connection between these two parts of the brain appears to have been damaged, so that the patient identifies a face as familiar but fails to associate any emotion with it. This creates a mental disconnect ("I see my wife but it generates no emotion"), and it seems that the brain's way of reconciling this mental issue is by convincing itself that the person they are seeing looks like their loved one but is an imposter. Ramachandran did some interesting laboratory experiments that strongly support his hypothesis.

The idiosyncracies of our behavior can be affected by the slightest physical changes in our brains.

04 March 2013

A different perspective on HIV news

Several news outlets ran laudatory articles about a baby who was cured of HIV infection after being put on anti-retrovirals 31 hours after birth. The press has greeted this finding with tremendous enthusiasm. Although my knowledge of HIV admittedly pales to that of an infectious disease specialist, I'm more guarded about the significance of this case report.

First, this finding has not yet been published in a scientific journal, so the scientific community cannot satisfactorily assess its credibility. Science has a tradition of peer-review, and it is frustrating that the press is trumpeting this "cure" when the rest of the scientific community doesn't have the tools to confirm its veracity.

But even if the report is confirmed, while it would be cool, I would think that it would constitute only a slight advance in our understanding of the disease.

Our current understanding of HIV is that once it gains a foothold in the body (by infecting particular reservoirs of dormant immune cells), it is impossible to eradicate completely. Our current medications can dramatically decrease the viral rate of replication and largely contain the virus to those cells that are already infected. Not only does this decrease the burden of disease and lengthen patients' lives, but being on antiretrovirals seems to reduce the infectivity of the bodily fluids of HIV-positive patients (e.g. their semen contains fewer virus particles).

According to press reports, this baby was found to have viral genetic material in his (or her) blood and was immediately started on antiretrovirals. In subsequent tests, although viral particles were detected, no evidence of active viral infection could be found.

The report of a cure strikes me as consistent with our current understanding of HIV works. If some of the baby's cells had been infected with HIV, but the infection had not yet made it into the reservoirs of dormant immune cells, then a cure would be a foreseeable outcome. It's the same reason why health-care workers are given antiretrovirals as prophylaxis when they get a needlestick from an HIV-infected patient: it decreases the odds that the viral infection will enter the reservoirs of dormant immune cells. In short, if this baby was "cured", it would probably mean that it had never been fully infected.

My guess is that this report will change the way that HIV-infected newborns are treated. There will be a new emphasis on detecting HIV infection and on starting therapy as soon as possible.

One point that people seem to be missing is that this baby was probably infected because her mother did not obtain prenatal care. Proper prenatal care dramatically reduces the likelihood of passing HIV to one's newborn. Is prenatal care easily accessible to all pregnant women? For all of this talk in the press of cure, I wish there was some mention of the very good tools of prevention we already possess.