Exon Publications, Brisbane, Australia
Polycystic Kidney Disease (PKD) is a common genetic disorder where multiple fluid-filled cysts develop in the kidneys, causing them to enlarge and lose function over time. This chapter provides an overview of PKD, starting with its definition and the types—Autosomal Dominant PKD (ADPKD) and Autosomal Recessive PKD (ARPKD). It explores the history and discovery of PKD, tracing its understanding from ancient observations to modern genetic research. The prevalence and demographics of PKD are examined, highlighting its widespread impact across different populations and age groups.
Keywords: Autosomal dominant polycystic kidney disease prevalence; Genetic mutations in polycystic kidney disease; Global demographics of polycystic kidney disease; Historical discovery of polycystic kidney disease; Incidence rates of polycystic kidney disease; Inheritance patterns of polycystic kidney disease; PKD genetic research history; Polycystic kidney disease epidemiology; Types of polycystic kidney disease; Understanding autosomal recessive polycystic kidney disease
Correspondence: Exon Publications, Brisbane, Australia. books@exonpublications.com
Cite as: Polycystic Kidney Disease: An Overview. In: Polycystic Kidney Disease: Public Education. Brisbane (AU): Exon Publications; 2024. Online first 2024 May 28. ISBN: 978-0-6458663-8-4.
Doi: https://doi.org/10.36255/polycystic-kidney-disease-overview
Copyright: Exon Publications.
License: This article is published under Attribution-NonCommercial-NoDerivatives license (BY-NC-ND 4.0) https://creativecommons.org/licenses/by-nc-nd/4.0/
Polycystic Kidney Disease (PKD) affects millions of people worldwide, yet it remains a condition that many are not fully aware of. PKD is a genetic disorder where numerous cysts form in the kidneys, eventually leading to reduced kidney function and other health complications. Understanding PKD involves looking at its different types—ADPKD and ARPKD—each with unique genetic causes and patterns of inheritance. This chapter aims to provide an understanding of PKD in a way that is easy to comprehend, helping readers with knowledge about this significant health condition. It examines the history of PKD, from early medical observations to the breakthroughs in genetic research that have shaped our current understanding. By exploring the prevalence and demographics of PKD, we can appreciate its impact on diverse populations globally (1–7).
Polycystic kidney disease, often shortened to PKD, is a genetic condition where many fluid-filled cysts develop in the kidneys. These cysts are like small balloons filled with liquid, and they can grow and multiply over time. As the cysts become larger and more numerous, they can cause the kidneys to enlarge and lose their ability to function properly.
There are two main types of PKD: Autosomal Dominant Polycystic Kidney Disease (ADPKD) and Autosomal Recessive Polycystic Kidney Disease (ARPKD). Each type is caused by different genetic mutations, which are changes in the DNA that affect how cells function, and has its own patterns of inheritance and symptoms. In ADPKD, the mutations usually occur in one of two genes, PKD1 or PKD2. The PKD1 gene is more common and tends to cause more severe disease. In ARPKD, the mutations occur in a gene called PKHD1. These genetic changes disrupt the normal development and function of the kidneys, leading to the formation of cysts.
ADPKD is the most common form of PKD. It is called "autosomal dominant" because only one parent needs to carry the gene for the disease to be passed on to their child. If a parent has ADPKD, there is a 50% chance that they will pass the condition to their child. This type of PKD typically shows symptoms later in life, usually between the ages of 30 and 50, although some people may start to have symptoms earlier or later. Common signs of ADPKD include high blood pressure, back or side pain, blood in the urine, and kidney stones. As the disease progresses, it can lead to chronic kidney disease and eventually kidney failure, requiring dialysis or a kidney transplant.
ARPKD is much rarer than ADPKD. It is called "autosomal recessive" because both parents must carry the gene for the disease, and a child must inherit two copies of the mutated gene to develop the condition. If both parents carry the gene, there is a 25% chance with each pregnancy that their child will have ARPKD. This type of PKD often becomes apparent much earlier in life, sometimes even before birth. Infants and children with ARPKD may have enlarged kidneys, which can be detected during an ultrasound. They might also have difficulty breathing due to underdeveloped lungs, liver problems, and high blood pressure. Unfortunately, ARPKD can be severe, and some affected babies may not survive infancy.
Although PKD primarily affects the kidneys, it can also cause problems in other parts of the body. People with PKD may develop cysts in the liver and pancreas, and they may have problems with their blood vessels, including an increased risk of aneurysms (weakened areas in the walls of blood vessels that can burst). They may also experience heart valve problems and hernias (where an organ pushes through an opening in the muscle or tissue that holds it in place).
The story of PKD begins many centuries ago. Historical records show that ancient physicians observed cases of enlarged kidneys in their patients, but they did not understand the cause. It was not until the advancement of medical science in the 19th and 20th centuries that significant progress was made in identifying and understanding PKD.
In the early 1800s, doctors began to document cases of enlarged, cyst-filled kidneys during autopsies. These findings were recorded in medical literature, but at that time, the understanding of genetics and the mechanisms behind diseases was very limited. Physicians could describe what they saw, but they could not explain why or how these cysts formed.
The term "polycystic kidney disease" itself was first used in the late 19th century. During this period, researchers started to recognize that PKD was a distinct condition, different from other kidney diseases. They noted that PKD often ran in families, suggesting a hereditary component. However, the exact mode of inheritance and the genetic basis of the disease were still unknown.
The real breakthrough came in the 20th century with the advent of modern genetics. In the 1930s and 1940s, scientists began to study the patterns of inheritance in families affected by PKD. They discovered that there were two main forms of the disease: one that appeared in adults and one that affected children. These were later identified as ADPKD and ARPKD, respectively.
The development of advanced imaging techniques in the mid-20th century, such as X-rays and ultrasounds, allowed doctors to diagnose PKD more accurately. These tools enabled them to see the cysts inside the kidneys without the need for surgery. This was a significant advancement, as it allowed for earlier detection and better monitoring of the disease's progression.
In the 1980s and 1990s, the field of genetics made remarkable strides. Researchers identified the specific genes responsible for PKD. For ADPKD, the primary genes involved are PKD1 and PKD2. Mutations in these genes lead to the development of cysts in the kidneys and other organs. For ARPKD, the gene identified was PKHD1. These discoveries were monumental because they provided a clear understanding of the genetic basis of PKD and opened the door for genetic testing and more targeted research.
The identification of these genes also led to the development of animal models of PKD. Scientists could now study the disease in the laboratory using mice and other animals that had similar genetic mutations. This research has been crucial in understanding how PKD develops and progresses, and it has been instrumental in testing potential treatments.
In recent years, there have been significant advancements in the treatment and management of PKD. The discovery of the drug tolvaptan, which can slow the growth of cysts and the decline in kidney function, marked a major milestone in PKD treatment. Clinical trials and ongoing research continue to explore new therapies and interventions that can improve the quality of life for those affected by the disease.
Today, we know much more about PKD than ever before, but the journey of discovery is far from over. Researchers around the world are working tirelessly to uncover new insights and develop better treatments.
PKD can be found in all parts of the world and affects people of all races and ethnicities. It is estimated that approximately 1 in 500 to 1 in 1,000 people have ADPKD, making it the most common form of PKD. This means that millions of individuals across the globe are living with this condition. ADPKD accounts for about 5% of all cases of chronic kidney disease worldwide, which highlights its significant impact on public health.
ARPKD is much rarer than ADPKD, occurring in about 1 in 20,000 live births. Although ARPKD is less common, it presents more severe symptoms, often appearing in infancy or early childhood. The early onset and serious nature of ARPKD make it a critical focus for early diagnosis and treatment.
In terms of demographics, PKD affects men and women equally. There is no significant difference in the prevalence of the disease between genders. Both men and women with ADPKD have the same likelihood of developing kidney cysts and experiencing related health issues. Similarly, ARPKD does not favor one gender over the other.
PKD is a significant genetic disorder that affects a large number of people worldwide. Understanding the disease's definition, types, history, and prevalence helps to paint a comprehensive picture of its impact on individuals and families. ADPKD and ARPKD, the two main types of PKD, each present unique challenges but are united by their genetic origins. The journey from ancient medical observations to modern genetic discoveries has been pivotal in improving diagnosis and treatment options. Recognizing the widespread nature of PKD across different demographics underscores the importance of continued research and awareness.
This article is part of our public education series. It was written by professional medical writers for the public using simple terms based on our medical book Polycystic Kidney Disease and articles indexed in PubMed, and further peer-reviewed for factual accuracy by independent experts. It is intended solely for informational purposes and is not to be considered medical advice. The views and opinions expressed in this article are believed to be accurate at the time of publication, but the publisher, editors, or authors cannot be held responsible or liable for any errors, omissions, or consequences arising from the use of the information contained in this article. The publisher makes no warranties, implicit or explicit, regarding the contents of this article or its use.
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