The Jeremiah Metzger Lecture. Polycystic kidney disease: old disease in a new context

I want to thank the organizers for inviting me to present the Jeremiah Metzger Lecture at this, the 114th meeting of the ACCA. It is a high honor, indeed, to join a list of very distinguished predecessors. And for this opportunity to tell you about my passion in medicine and science, I am most grateful. Most of you in this room have passing knowledge of polycystic kidney disease, probably hearing about it in your medical school Pathology course where you were shown an especially grotesque, enormously enlarged kidney either encased in transparent plastic or submerged in a bucket of formaldehyde. In that minute or two when PKD was discussed in lecture, you may have been told that this is a rare, hereditary disorder that causes kidney failure and that nothing can be done to alter that course. Unless you chose to specialize in General Internal Medicine or Nephrology, you may not have encountered PKD again until today, despite the fact there are approximately 600,000 PKD patients in the USA and over 10,000,000 worldwide, and it accounts for approximately 5% of non-diabetic dialysis and renal transplant patients (Table 1). I might have overlooked PKD as well had it not been for a close friend that I grew up with who had inherited the disease from his mother. He was very open about the fact that he had cysts in his kidneys that caused bleeding into the urine from time to time, especially after a solid hit during a game of tackle football. We remained friends long after I left home for college and medical school. At an early stage of my research career in medicine, while wondering how nephron segments processed glomerular filtrate, I inadvertently discovered that renal tubules could secrete as well as reabsorb salt and water. This was quite an unexpected finding at the time (1). But it occurred to [table: see text] me that this might be a means to fill renal cysts with fluid and so I decided to learn more about the pathology and pathogenesis of PKD. This didn't take long, because there wasn't much literature on the subject. The clinical manifestations of PKD were described in the 19th century European medical literature and Sir William Osler had published on the topic in this country, but by and large only a few descriptions of small groups of patients were reported through the middle of the 20th century. In 1957, Dalgaard (2) reported in a classic doctoral thesis that the most common type of hereditary PKD is transmitted as an autosomal dominant trait (ADPKD) with complete penetrance. It is a bilateral renal condition, but cysts also occur in the liver (approximately 60%), pancreas (approximately 10%) and various other organs, and it is associated with cerebral aneurysms in approximately 5% of patients. A recessive form that affects infants and children primarily (ARPKD), is much rarer than ADPKD and commonly leads to death in infancy in association with massively enlarged kidneys (Table 2). I was also attracted to the study of PKD because the etiology was not in question: it had to be mutated DNA. Yet that fact proved to be a hindrance in attaining research support. As some of you will recall, not too long ago genetic diseases were viewed by kidney-oriented NIH review panels to be incurable. I was advised that a young scientist's time would be better spent determining how the kidneys excrete salt and water. Fortunately, the era of molecular genetics and biology was upon us, and we quickly learned that uncommon genetic disorders could lead to the discovery of novel molecules in metabolic and structural pathways. And that is just what happened in the PKD field. The autosomal dominant form of PKD led to the discovery of a unique family of highly complex proteins long before they would have been selected from a gene or proteomic micro-array by some desperate graduate student or fellow. The chromosomal location of the major ADPKD genotype, PKD1, was defined in 1985 (3), a date that marks the beginning of a remarkable period of discovery.