Polycystic Kidney Disease and Other Inherited Disorders of Tubule Growth and Development¶
Chapter 327 | Part 9: Disorders of the Kidney and Urinary Tract
KEY CLINICAL POINTS¶
- ADPKD is the most common monogenic cause of kidney failure, with autosomal dominant inheritance, while ARPKD is autosomal recessive and primarily affects children.
- Ciliary defects in PC1/PC2 proteins disrupt signaling pathways (Wnt, mTOR, cAMP) and contribute to cystogenesis, linking ADPKD and ARPKD to ciliopathies.
- Genetic testing is critical for diagnosis, with PKD1 (85%) and PKD2 (15%) mutations responsible for ADPKD, and PKHD1 mutations for ARPKD.
- Management focuses on blood pressure control (target <140/90 mmHg), tolvaptan for slowing cyst growth, and surgical interventions for complications like ICA aneurysms.
- Complications include ESRD, cardiovascular disease, renal cell carcinoma, and hepatic fibrosis, with variable penetrance and expressivity.
1. DEFINITION & OVERVIEW¶
Polycystic kidney diseases (PKD) are genetically heterogeneous disorders characterized by progressive renal cyst formation. ADPKD is the most common life-threatening monogenic cause of kidney failure, while ARPKD is a rare autosomal recessive disorder affecting pediatric populations. Ciliopathies, including ADPKD and ARPKD, involve defects in primary cilia function, leading to disrupted signaling pathways and cystogenesis.
Table 327-1: Inherited Diseases Commonly Associated with a Cystic Phenotype¶
| DISEASE | MODE OF INHERITANCE | RENAL ABNORMALITIES | OTHER CLINICAL FEATURES | GENES |
|---|---|---|---|---|
| Autosomal dominant polycystic kidney disease | AD | Bilaterally enlarged kidneys with cortical and medullary cysts | Liver, pancreatic cysts, hypertension, subarachnoid hemorrhage | PKD1, PKD2 |
| Autosomal recessive polycystic kidney disease | AR | Distal and collecting duct cysts | Oligohydramnios, hypertension, ascending cholangitis, liver fibrosis | PKHD1 |
| Renal cysts and diabetes syndrome | AD | Kidney cysts, aberrant nephrogenesis | Diabetes, hyperuricemic nephropathy | HNF1B |
| DISEASE | MODE OF INHERITANCE | RENAL ABNORMALITIES | OTHER CLINICAL FEATURES | GENES |
|---|---|---|---|---|
| Senior-Loken syndrome | AR | Renal cysts | Juvenile nephronophthisis, Leber amaurosis | NPHP1-6, SDCCAG8 |
| Meckel-Gruber syndrome | AR | Cortical and medullary cysts | CNS anomalies, polydactyly, congenital heart defects | MKS1, TMEM216, TMEM67, TMEM231, TMEM107, CEP290, RPGRIP1L, CC2D2A, TCTN2, B9D1, B9D2, NPHP3, KIF14 |
| Bardet-Biedl syndrome | AR | Renal cysts | Obesity, polydactyly, retinitis pigmentosa, congenital heart defects | BBS1, BBS2, BBS4, BBS5, BBS7, BBS9, BBS12, MKS1, CEP290, C2ORF86 |
| Von Hippel-Lindau disease | AD | Renal cysts | Renal cell carcinoma, retinal angiomas, CNS hemangioblastomas | VHL |
1.1 Subtopic¶
ADPKD (autosomal dominant) and ARPKD (autosomal recessive) are distinct entities. ADPKD is caused by mutations in PKD1 (85%) or PKD2 (15%), while ARPKD is linked to PKHD1 mutations. Both are classified as ciliopathies due to defects in primary cilia, which regulate critical signaling pathways.
2. EPIDEMIOLOGY¶
ADPKD affects 1 in 1000–400 individuals globally, with 50% of patients diagnosed by age 50. ARPKD is rarer, with prevalence estimated at 1 in 20,000 live births. Risk factors include family history, male gender (for Mesoamerican nephropathy), and environmental exposures. Ethnicity does not significantly affect prevalence.
2.1 Demographics¶
ADPKD affects all ethnic groups, while ARPKD is more common in males (Mesoamerican nephropathy). Genetic counseling is critical for families with a history of ciliopathies.
3. ETIOLOGY & PATHOPHYSIOLOGY¶
ADPKD is caused by mutations in PKD1 (85%) or PKD2 (15%), encoding polycystin-1 (PC1) and polycystin-2 (PC2). These proteins form a receptor-channel complex on primary cilia, regulating calcium signaling, Wnt, and mTOR pathways. ARPKD is linked to PKHD1 mutations, causing fibrocystin/polyductin (FPC) defects. Ciliary dysfunction disrupts cell proliferation, fluid secretion, and mechanosensation.
4. CLINICAL FEATURES¶
ADPKD presents with progressive renal cysts, hypertension, liver cysts, and intracranial aneurysms (ICA). ARPKD manifests as congenital hepatic fibrosis, Caroli disease, and renal enlargement in neonates. Other syndromes include Tuberous Sclerosis (TS) with angiomyolipomas and Von Hippel-Lindau (VHL) with renal cell carcinoma.
4.1 ADPKD Manifestations¶
Renal cysts, hypertension, liver and pancreatic cysts, ICA aneurysms, and chronic kidney disease (CKD).
4.2 ARPKD Manifestations¶
Congenital hepatic fibrosis, Caroli disease, renal enlargement, and neonatal respiratory failure due to oligohydramnios.
5. DIFFERENTIAL DIAGNOSIS¶
Distinguish from other ciliopathies (e.g., Senior-Loken syndrome, Bardet-Biedl syndrome), renal cysts with diabetes (HNF1B mutations), and non-cystic renal diseases. Consider TS, VHL, and MCKD in differential diagnosis.
6. INVESTIGATIONS & DIAGNOSIS¶
Diagnosis relies on imaging (ultrasound, CT, MRI) and genetic testing. Ultrasound detects ≥ 2 renal cysts in adults ≥ 15 years. CT/MRI are more sensitive for small cysts. Genetic testing confirms PKD1/PKD2 or PKHD1 mutations. Criteria for diagnosis vary by age group (sensitivity 96–100% for adults).
6.1 Imaging Criteria¶
Ultrasound: ≥ 2 cysts in adults ≥ 15 years. CT/MRI: ≥ 2 cysts in each kidney for adults ≥ 30 years. Sensitivity 100% for ≥ 4 cysts in each kidney.
7. MANAGEMENT & TREATMENT¶
Blood pressure control (target <140/90 mmHg), tolvaptan (V2R antagonist) for slowing cyst growth, and surgical interventions for complications. Everolimus and sirolimus target mTOR pathways. Renal transplantation is considered for end-stage renal disease (ESRD).
7.1 Pharmacologic Therapies¶
Tolvaptan (FDA-approved for rapidly progressing ADPKD), sirolimus/everolimus (mTOR inhibitors), and antihypertensives (ACE inhibitors, ARBs).
7.2 Surgical Interventions¶
Nephrectomy for massive kidneys, ICA screening with MRI, and nephron-sparing surgery for renal tumors.
8. PROGNOSIS & COMPLICATIONS¶
ADPKD leads to ESRD in late middle age, with cardiovascular complications as the leading cause of mortality. ARPKD has severe complications in neonates, including respiratory failure. Complications include renal cell carcinoma, hepatic fibrosis, and ICA aneurysms.
9. SPECIAL CONSIDERATIONS¶
Pregnancy in ADPKD requires monitoring for ICA aneurysms and renal function. Pediatric ARPKD requires early intervention for oligohydramnios. TS patients need surveillance for renal cell carcinoma. Mesoamerican nephropathy is linked to environmental toxins and heat stress.
10. KEY POINTS & CLINICAL PEARLS¶
- Genetic testing is essential for confirming PKD variants. 2. Tolvaptan is FDA-approved for rapidly progressing ADPKD. 3. Ciliary dysfunction underlies both ADPKD and ARPKD. 4. Monitor for ICA aneurysms in ADPKD patients. 5. Renal transplantation is indicated for ESRD.