In response to your questions:
1 – you should not worry about any of this until you have a conclusive diagnosis of BHD with a gene test. It could be that your fibrofolliculomas are not caused by BHD, which would allow you to stop worrying about the other manifestations of the disease.
2 – the genes that cause hereditary breast cancer and kidney cancer are different, meaning that they cannot be regarded as the same disease. The most common cause of hereditary breast cancer is mutation of the BRCA1 or BRCA2 genes. As you state, if you have these mutations, there is a high chance of developing breast cancer, which is why patients sometimes opt to have a preventative mastectomy. A number of studies have analysed the risk of developing kidney cancer in BHD, and have found that roughly only 30% of patients with a FLCN mutation will go on to develop kidney cancer.
3 – due to the underlying genetic differences of BRCA breast cancer and BHD-associated kidney cancer, the tumours have different characteristics. Breast cancers can be quite aggressive and are more likely to metastasise and spread in the body, which is usually the life-threatening aspect of cancer. The kidney tumours that BHD patients get are usually very benign in their behaviour. They grow slowly and they rarely metastasise. There are very few reported cases of this particular type of cancer causing a patient to die, whereas mortality due to breast cancer is, unfortunately, not uncommon. In the few cases where a BHD patient has died from metastatic kidney cancer, it is usually because they were not known to have BHD, and by the time they were found to have kidney cancer, the disease was already very advanced.
4 – regarding preventative kidney removal and transplant. Given that the kidney tumours seen in BHD are not very aggressive and are rarely life-threatening, this would not be a sensible or necessary course of action. Mastectomies are performed because breasts are not necessary to support life, and because breast cancer is both aggressive and common, such preventative action saves many lives. On the other hand, kidneys are a vital organ, and the tumours found in BHD are rarely life-threatening. Additionally, transplant organs are not always permanent or curative. It is possible the body could reject an organ at any time, and any patient with a transplant needs to be closely monitored, and sometimes on strong medications, for the rest of their life. Therefore, by removing kidneys and transplanting new ones, in this case it would cause much more harm to the patient than the kidney cancer is doing in the first place.
5 – Regarding other cancers. There are a few other cancers that MAY be associated with the disease. To my knowledge, liver cancer is not one of them. Colon cancer has been reported to perhaps be linked, but a number of studies trying to investigate this have shown this to be inconclusive. Colon cancer is a fairly common cancer, meaning that those with BHD who have also had colon cancer may have been unlucky and developed colon cancer independently from their BHD. Or there could be a link. There are so few cases of this happening, that it is not possible to do meaning research or statistics. At present, the only conclusively linked symptoms of BHD are fibrofolliculomas, lung cysts and kidney cancer.
6 – There is a 50x higher risk of BHD patients developing pneumothorax compared to the normal population, yes. Current estimates show that roughly 25% (or 1 in 4) of BHD patients have episodes of collapsed lung.
7 – Lung CT or MRI to image the lungs would work. CTs do give out small doses of X-ray radiation, yes, so wouldn’t be performed unless it was necessary. However, the chances of a CT scan having a negative effect on your health are very small. Currently, beyond a scan to determine whether or not you have lung cysts, there is no set guideline as to how often to monitor the lungs, so on-going monitoring for the lungs is not performed as often as it would be for the kidneys.
The BHD Foundation/ Myrovlytis Trust