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PubMed This is a summary of 15 peer-reviewed journal articles Updated
Nephrology

The Biology of Cysts: Genes and Cells

At a Glance

ADPKD is primarily caused by inherited mutations in the PKD1 or PKD2 genes. These mutations disrupt tiny cellular sensors called primary cilia, causing a chemical buildup that triggers kidney cells to multiply uncontrollably and form fluid-filled cysts.

While ADPKD might seem like a simple case of “cysts on the kidneys,” the biology behind it is a complex story of genetic “switches” and tiny cellular sensors. Understanding how these mutations lead to cyst growth can help you better understand why certain treatments work and how your doctor distinguishes ADPKD from other similar conditions [1][2].

The Genetic Blueprint: PKD1 and PKD2

Almost all cases of ADPKD are caused by a mutation in one of two genes: PKD1 (located on chromosome 16) or PKD2 (located on chromosome 4) [3]. These genes provide the instructions for making two proteins, polycystin-1 and polycystin-2, which work together like a lock and key [4][5].

  • PKD1 Mutations: These are the most common (about 75-85% of cases) and generally lead to more cysts and an earlier decline in kidney function [6][7].
  • PKD2 Mutations: These are typically less severe, with cysts appearing later in life and kidney function remaining stable for longer [7][8].

The “Second-Hit” Hypothesis

You might wonder why, if every cell in your kidney has the ADPKD mutation, only some cells turn into cysts. This is explained by the “second-hit” hypothesis [9][10].

  1. The First Hit: You are born with one mutated copy of the gene in every cell (inherited from a parent) [9].
  2. The Second Hit: Over time, a random “accident” or second mutation occurs in the other healthy copy of the gene within a single kidney cell [10].
    Once that specific cell loses both functional copies of the gene, it begins to multiply uncontrollably and secrete fluid, eventually forming a cyst [9][11].

Tiny Sensors: The Role of Primary Cilia

The polycystin proteins live on primary cilia—tiny, hair-like structures on the surface of your kidney cells [4][12]. These cilia act like “antennae” or sensors that detect the flow of urine [12]. In ADPKD, the “antennae” are broken. This broken signal causes a chemical called cAMP to skyrocket inside the cell [12][2]. High cAMP levels act like “gasoline,” telling the cell to divide rapidly and pump fluid into the growing cyst [12][2].

Is it Really ADPKD? (Differential Diagnosis)

Because there are other rare genetic conditions that cause kidney cysts, doctors must ensure an accurate diagnosis to provide the right care. For example, if a patient presents with severe disease very early in life, doctors may rule out Autosomal Recessive PKD (ARPKD), which is caused by a completely different gene [3][13]. By analyzing your family history, clinical symptoms, and sometimes utilizing genetic testing, your medical team will confirm that your cysts are indeed caused by ADPKD, allowing for the most effective and personalized management strategy [14][15].

Common questions in this guide

What is the difference between PKD1 and PKD2 mutations?
PKD1 mutations are the most common cause of ADPKD and generally lead to more cysts and an earlier decline in kidney function. PKD2 mutations are usually less severe, with cysts appearing later in life and kidney function remaining stable for longer.
Why do only some kidney cells turn into cysts in ADPKD?
Cyst growth is explained by the 'second-hit' hypothesis. You inherit one mutated gene in all cells, but a cyst only forms when a random second mutation occurs in the healthy copy of the gene within a single kidney cell, causing it to multiply and secrete fluid.
What are primary cilia and how do they relate to ADPKD?
Primary cilia are tiny, hair-like structures on kidney cells that act as sensors for urine flow. In ADPKD, these sensors are broken, which causes a chemical called cAMP to build up and trigger rapid cyst growth.
Can a genetic test confirm my ADPKD diagnosis?
Yes, genetic testing can analyze the PKD1 and PKD2 genes to confirm an ADPKD diagnosis. This helps distinguish ADPKD from other rare genetic conditions that cause kidney cysts, ensuring you get the most accurate treatment plan.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Was my diagnosis based on an ultrasound, or have we confirmed it with a genetic test for the PKD1 or PKD2 genes?
  2. 2.Based on my family history and imaging, how likely is it that I have a contiguous gene syndrome?
  3. 3.Does my specific mutation (truncating vs. non-truncating) typically lead to a faster or slower progression of the disease?
  4. 4.Are there specific markers in my blood or urine that suggest my cAMP levels are high, and would that make me a candidate for certain treatments?
  5. 5.Could any of my symptoms be explained by other conditions, or do my imaging results clearly point to ADPKD?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (15)
  1. 1

    Management of Autosomal Dominant Polycystic Kidney Disease (ADPKD) During Pregnancy: Risks and Challenges.

    McBride L, Wilkinson C, Jesudason S

    International journal of women's health 2020; (12()):409-422 doi:10.2147/IJWH.S204997.

    PMID: 32547249
  2. 2

    Metabolic Reprogramming in Autosomal Dominant Polycystic Kidney Disease: Evidence and Therapeutic Potential.

    Nowak KL, Hopp K

    Clinical journal of the American Society of Nephrology : CJASN 2020; (15(4)):577-584 doi:10.2215/CJN.13291019.

    PMID: 32086281
  3. 3

    Copy Number Variation: A New Genetic Form of Polycystic Kidney and Liver Disease.

    Fujimaru T, Sohara E

    Kidney international reports 2020; (5(5)):575-576 doi:10.1016/j.ekir.2020.03.007.

    PMID: 32406422
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    Autosomal dominant PKD gets an atomic map.

    Welling PA

    Nature reviews. Nephrology 2018; (14(12)):725-726 doi:10.1038/s41581-018-0066-7.

    PMID: 30279534
  5. 5

    The ion channel function of polycystin-1 in the polycystin-1/polycystin-2 complex.

    Wang Z, Ng C, Liu X, et al.

    EMBO reports 2019; (20(11)):e48336 doi:10.15252/embr.201948336.

    PMID: 31441214
  6. 6

    Gene Panel Analysis in a Large Cohort of Patients With Autosomal Dominant Polycystic Kidney Disease Allows the Identification of 80 Potentially Causative Novel Variants and the Characterization of a Complex Genetic Architecture in a Subset of Families.

    Mantovani V, Bin S, Graziano C, et al.

    Frontiers in genetics 2020; (11()):464 doi:10.3389/fgene.2020.00464.

    PMID: 32457805
  7. 7

    Case report: Genotype-phenotype characteristics of nine novel PKD1 mutations in eight Chinese patients with autosomal dominant polycystic kidney disease.

    Zhuang J, Aierken A, Yalikun D, et al.

    Frontiers in medicine 2023; (10()):1268307 doi:10.3389/fmed.2023.1268307.

    PMID: 37901409
  8. 8

    Evaluating gene variations in autosomal dominant polycystic kidney disease patients using whole exome sequencing and phenotype to genotype analysis.

    Aypek H, Balaban RF, Huriyet N, et al.

    Renal failure 2025; (47(1)):2547306 doi:10.1080/0886022X.2025.2547306.

    PMID: 41032671
  9. 9

    Progress in the understanding of polycystic kidney disease.

    Torres VE, Harris PC

    Nature reviews. Nephrology 2019; (15(2)):70-72 doi:10.1038/s41581-018-0108-1.

    PMID: 30607031
  10. 10

    Detection of PKD1 and PKD2 Somatic Variants in Autosomal Dominant Polycystic Kidney Cyst Epithelial Cells by Whole-Genome Sequencing.

    Zhang Z, Bai H, Blumenfeld J, et al.

    Journal of the American Society of Nephrology : JASN 2021; (32(12)):3114-3129 doi:10.1681/ASN.2021050690.

    PMID: 34716216
  11. 11

    Somatic Mutations in Renal Cyst Epithelium in Autosomal Dominant Polycystic Kidney Disease.

    Tan AY, Zhang T, Michaeel A, et al.

    Journal of the American Society of Nephrology : JASN 2018; (29(8)):2139-2156 doi:10.1681/ASN.2017080878.

    PMID: 30042192
  12. 12

    Cilia-Localized Counterregulatory Signals as Drivers of Renal Cystogenesis.

    Walker RV, Maranto A, Palicharla VR, et al.

    Frontiers in molecular biosciences 2022; (9()):936070 doi:10.3389/fmolb.2022.936070.

    PMID: 35832738
  13. 13

    Autosomal dominant polycystic kidney disease diagnosed in utero. Review.

    Nowak M, Huras H, Wiecheć M, et al.

    Ginekologia polska 2016; (87(8)):605-8 doi:10.5603/GP.2016.0053.

    PMID: 27629138
  14. 14

    Insights into Autosomal Dominant Polycystic Kidney Disease from Genetic Studies.

    Lanktree MB, Haghighi A, di Bari I, et al.

    Clinical journal of the American Society of Nephrology : CJASN 2021; (16(5)):790-799 doi:10.2215/CJN.02320220.

    PMID: 32690722
  15. 15

    Cystic Kidney Diseases That Require a Differential Diagnosis from Autosomal Dominant Polycystic Kidney Disease (ADPKD).

    Sekine A, Hidaka S, Moriyama T, et al.

    Journal of clinical medicine 2022; (11(21)) doi:10.3390/jcm11216528.

    PMID: 36362756

This page explains the genetic and cellular biology of ADPKD for educational purposes. It does not replace professional medical advice or genetic counseling from your healthcare provider.

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