[Sparrowhawk (OP)]

Why is there massive weight loss at the end stage of AIDS?


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[chris]

AIDS patients usually suffer several simultaneous opportunistic infections, including atypical mycobacterial infections (forms of TB), PCP (pneumocystis carinii), yeast infections (candida, cryptococcus), herpesvirus infections (cytomegalovirus, EBV, HSV and VZV), protozoal infections (toxoplasmosis, cryptosporidium), other viruses (JC and BK) and other bacteria. Sufferers can also develop malabsorption syndromes and chronic diarroea.

These opportunist infections begin to gain a foothold as the immune system falters, usually once the CD4 count (the white blood cells targeted by HIV) falls below a threshold level of between 50 and 100, though often when it reaches 200.

Once these infections become entrenched the body becomes metabolically burdened in trying to deal with them. At the same time, what remains of the immune system attempts to fight them off, often producing high levels of inflammatory cytokines to recruit and marshall other immune responses who's role it is to combat invaders of these sorts.

But because the immune system is disabled, this amounts to the chemical and hormonal equivalent of a lot of hot air and little action. And unfortunately these inflammatory mediators also have the side effect of suppressing appetite, which further compounds weight loss.

Added to this is the effect of antiretroviral drugs, which can cause dyslipidaemias and disorders of fat metabolism called lipodystrophy; patients show strange redistributions of fat around the body, often developing very gaunt, skeletal looking faces.

Helen Carter has written a really excellent account of HIV and AIDS, including the drugs that can be used to treat it. Here's the link:

http://www.thenakedscientists.com/HTML/articles/article/25yearsofhivaidsintheuk/

Chris

[Sparrowhawk (OP)]

OK, so you are saying that there is a combination of appetite suppression, malabsorption and increased metabolic rate. I don't think that this type of weight loss is usually seen in those who die from other infectious diseases is it? It is seen in cancer sufferers though and the weight loss seems to be very rapid in a similar way to aids - can this just be due to loss of appetite? I just wondered if there have been any studies on it?

[iko]

OK, so you are saying that there is a combination of appetite suppression, malabsorption and increased metabolic rate. I don't think that this type of weight loss is usually seen in those who die from other infectious diseases is it? It is seen in cancer sufferers though and the weight loss seems to be very rapid in a similar way to aids - can this just be due to loss of appetite? I just wondered if there have been any studies on it?

Wrong.  Untreated chronic infectious diseases do exactly this. Tuberculosis is a typical case in point.

...
In the past, tuberculosis has been called consumption, because it seemed to consume people from within, with a bloody cough, fever, pallor, and long relentless wasting. Other names included phthisis (Greek for consumption) and phthisis pulmonalis; scrofula (in adults), affecting the lymphatic system and resulting in swollen neck glands; tabes mesenterica, TB of the abdomen and lupus vulgaris, TB of the skin; wasting disease; white plague, because sufferers appear markedly pale; king's evil, because it was believed that a king's touch would heal scrofula; and Pott's disease, or gibbus of the spine and joints.[7][8] Miliary tuberculosis – now commonly known as disseminated TB – occurs when the infection invades the circulatory system resulting in lesions which have the appearance of millet seeds on X-ray.[7][9]

http://en.wikipedia.org/wiki/Tuberculosis

[Sparrowhawk (OP)]

Thanks Iko.  I find it hard to think of many chronic infectious diseases for comparison. Presumably acute infection kills you before there is time for weight loss.  What about leprosy?  What I was really wondering about is whether anyone has tried measuring energy intake vs activity in AIDS/cancer sufferers to see whether there is an increase of energy expenditure of unknown or known cause. Perhaps, as Chris says, it is simply increased general inflammatory-type response to the infection since the immune response is no longer happening.
I found this on the web "Despite major advances in the treatment and survival of patients infected with human immunodeficiency virus (HIV), weight loss and wasting remain common problems. In the HIV-infected population, weight loss is associated with lower CD4+ cell counts and is an independent predictor of mortality. The etiology of weight loss and wasting is complex and multifactorial."