Autosomal Dominant Polycystic Kidney Disease (ADPKD)
ADPKD is a multisystemic, progressive disorder characterized by the development and expansion of multiple cysts in the kidneys, ultimately leading to end-stage renal disease (ESRD).
1. Pathophysiology
- Genetics: Mutations in PKD1 (chromosome 16, ~85% of cases, more severe) or PKD2 (chromosome 4, ~15% of cases, milder).
- Mechanism: Mutations affect polycystin proteins in primary cilia, leading to abnormal tubular epithelial cell proliferation and fluid secretion, causing cyst formation.
2. Associated Extra-Renal Findings
| Finding | Clinical Significance |
|---|---|
| Berry Aneurysms | Increased risk of subarachnoid hemorrhage (Circle of Willis). |
| Hepatic Cysts | Most common extra-renal manifestation; usually asymptomatic. |
| Mitral Valve Prolapse | Associated valvular abnormality. |
3. Exam Must-Knows
- Presentation: Often presents in the 3rd or 4th decade of life with flank pain, hematuria, hypertension, and palpable kidney masses.
- Autosomal Recessive (ARPKD): Distinct from ADPKD; presents in infancy, involves congenital hepatic fibrosis and Potter sequence (pulmonary hypoplasia, oligohydramnios).
Pathology Board Hint: For board exams, ADPKD is the “berry aneurysm” disease. If a vignette describes a patient with hypertension, hematuria, and a family history of kidney failure, look for an extra-renal association like a “berry aneurysm” or “hepatic cyst.”