Mechanisms Versus Causes in Biology and Medicine - Mechanism and Causality in Biology and Economics - page 25

important in medicine, so now we turn to an example from that field. The example
shows that knowledge of the mechanisms operating or failing to operate provides a
better handle than knowing that a single “X causes disease Y.”
4 Control of the Outcome in the Disease of Cystic Fibrosis
One might say: “A mutation in the CFTR gene causes the disease cystic fibrosis.”
But this is an impoverished claim, compared to a description of the myriad
mechanisms involved in the etiology of the disease.
In medical contexts, the puzzling phenomenon may be described and
redescribed in various ways, as work proceeds to discover the mechanisms produc-
ing the disease. Also, the phenomenon of interest is different for those attending to
different stages in the progress of the disease. Yet other characterizations of the
phenomenon may be provided by those doing fundamental research versus those
tasked with treating patients, so this case also illustrates different ways of
characterizing the phenomenon within the contexts of pure versus applied research.
Different characterizations of the phenomenon focus attention on different
mechanisms or stages of a given mechanism involved in the disease etiology.
The phenomenon to be explained in what has come to be called the disease of
“cystic fibrosis” changed over time, as groups of symptoms were clustered, the gene
discovered, some of the activities of the malfunctioning protein found, and later
stages of the disease dissected. One can tell a tidy story about the discovery of the
normal mechanism, about the many ways it can break, and about how this knowl-
edge has been and is being used in designing drug therapy. This perspective views
disease as a broken-normal mechanism and therapy as aimed at restoring normal
functioning (Moghaddam-Taaheri 2011 ).
However, one can view the medical mechanistic picture in a more complex way.
One can ask: Is there some other mechanism that can restore chloride transport
function rather than fixing the broken mechanism? Alternatively, as is common in
medicine, one can just focus on mechanisms that will aid in alleviation of
symptoms of those living with the disease. More specifically, one can seek drugs
that will aid in preventing the lung infections that typically lead to death for cystic
fibrosis patients. For some of these cases, the current understanding of the
mechanisms provides powerful tools for medical researchers, but for other cases
many black boxes remain.
In the early 1990s, it looked as if the story of conquering cystic fibrosis would be
a simple one: gene discovered, mechanism and mutations understood, and guidance
provided for therapies for intervention. However, the genotype-phenotype relations
are more complex than anyone studying a disease (seemingly) produced by a single
gene defect had reason to expect. Some aspects of the connections between the gene
mutations and protein defects and the many phenotypic symptoms of the disease are
still not well understood.