I have been seeing a number of women coming to clinic with a shared presentation of a similar condition, which used to be considered quite rare, but we (and others) have been seeing quite a lot of it. The prototypical case might go something like this: A 35 year old woman comes in because of an ulcerating sore on her left breast draining pinkish, transparent watery fluid (serosanguineous). She has a firm, palpable mass in her right breast and a history of having two prior episodes of similar breast problems which were treated with incision and drainage in her native Mexico. She has had two children and breastfed both, although she hasn’t been breastfeeding for the last two years. The patient will be worked up to rule out breast cancer and end up with a diagnosis of idiopathic granulomatous mastitis (IGM).
What is granulomatous mastitis? By the inclusion of the term “idiopathic”, the medical community is acknowledging that they don’t know what is going on, but it is believed to be an autoimmune/inflammatory condition, and perhaps you can think of it as Crohn’s Disease of the breast. It can be extremely uncomfortable and sometimes quite painful, often with all the socio-cultural implications of diseases of the breast, which can be quite distressing to patients.
Idiopathic granulomatous mastitis used to be considered quite rare and was not identified as a condition until the 70’s; however, here in Northern California we have been seeing it in many patients, particularly women from Latin America with a history of breast feeding. However, we are not the only ones who have observed this trend. It’s been reported in Indiana (2009) and in New York City (2014).
So what might be causing this? At a high level, we can think about causes as being genetic or environmental. Although these cases of IGM are occurring in a particular population, namely women ethnically defined as Latino, that’s not a very good standing for a genetic basis. Although there are certainly genetically well defined indigenous groups in Latin America, for example Maya or Nahua groups, modern Latin Americans represent highly admixed genetics, with ancestry including not only these indigenous peoples, but European, African, and Asian ancestors. It is possible that there might be what is called a “founder effect”, where a particular ancestor contributed risk genes which are bouncing around in the population, so it is worth thinking about about genetic susceptibility. However, given that this might be a recent upsurge of the condition in a varying genetic background, associated with a cultural/geographic distribution, and a particular exposure (pregnancy/breastfeeding), I think an environmental exposure much more likely.
What sort of environmental exposure might be at fault? Given that a history of breastfeeding seems to be one common feature that links most of the women together, that might be a prime place to look. Given the shared cultural background, there might be some unique environmental exposures in this group. In the US, there are any number of products on the market to help nursing/weaning mothers. Some are naturopathic, such as herbal teas to encourage milk production. There are also many different salves and creams for treating sore nipples for nursing mothers, many which are made with a range of herbal products. These herbal and natural products are typically not well characterized in terms of toxicity and pharmacology. Is there one of these products, perhaps a new on on the market, that nursing mothers from Mexico are using? Maybe there is a folk treatment which is at fault. Or maybe there is a folk treatment where the original substances are not available any more, so something is being substituted here which is contributing to the problem.
Could the exposure be infectious? As children are weaning, they may be consuming a mixed diet, including other milk products or formulas. Are babies cross contaminating their mothers with a bacteria derived from unpasteurized milk products? Mastitis commonly effects milk producing domestic animals, and often has an infectious etiology. Are babies exposing their mother’s nipples to Corynebacterium bovis? Maybe this is causing a subacute infection inducing an inflammatory response which takes a while to manifest and then persists? Is there a formula or perhaps a pureed plant product that is inducing some sort of inflammatory reaction or containing a microbe we don’t know about?
There is a good opportunity to do some epidemiology here to discover agents linked to the disease to give some clues as to its cause and maybe guide prevention and treatment.
Do you have any ideas? Does anyone know anything about current practices trends for nursing mothers in Mexico, particularly with regards to topical treatments or diets in weaning?
It is probably worth mentioning that this blog post is in no way intended to discourage anyone from beast feeding their children. The key benefits of this are well established in research literature. There is however, some limited epidemiological evidence that has linked breastfeeding to granulomatous mastitis in a small number of women, and it is worth trying to understand what is happening to help prevent this from happening to other women.