25th European Congress Pathology August-September 2013 Lisbon Slide Seminar Electron Microscopy/Nephropathology Electron microscopy in focus: native and transplanted Kidney.

Inherited kidney diseases Importance of Electron Microscopy for diagnosis Fernanda Carvalho Nephrology Department Curry Cabral Hospital, “CHLC”, Lisbon

22 years old caucasian female. Serum creatinine – 1.9 mg/dL (routine analyses). Hypertension since 16 years old. Hyperuricemia. Case presentation - 1

Several close relatives with CKD autosomal dominant, cysts and/or gout. Some of them were in CKD stage 5, hemodialysis or transplanted. Renal ultrasound: Kidney with normal size and cortico- medullar differentiation. Bilateral cortico/medular cysts. Case presentation - 2

Urinary sediment – irrelevant Without : –Proteinuria –Hematuria –Earing loss Case presentation - 3

Pedigree analysis Filled symbols, affected individuals; open symbols, unaffected individuals; slash, deceased; HD, hemodialysis; KT, kidney transplantation; CKD, chronic kidney disease. Arrow identifies proband. Case presentation - 4

In short : Non proteinuric inherited renal phenotype, transmitted in an autosomal dominant pattern. Affected individuals displayed hyperuricemia/gout and/or renal cysts. Case presentation - 5

Differential diagnosis ADPKD Medullary cystic kidney disease / Familial juvenile hyperuricemic nephropathy Case presentation - 6

A kidney biopsy was performed Case presentation - 7

LM: Striking features in the biopsy were: Interstitial nephritis, thickened tubular basement membranes. Cytoplasmatic inclusions in tubular distal cells. Kidney Biopsy

Kidney Biopsy LM

EM: On EM there is swelling of endoplasmic reticulum cisternae. With discret granular inclusions inside. Kidney Biopsy

Electron Microscopy

Normal endoplasmatic reticulum Electron Microscopy

Kidney Biopsy IHC

Diagnosis Interstitial nephritis. Dense citoplasmatic inclusions in tubular distal cells. On electron microscopy - swelling of ER, due to the accumulation of uromodulin. + Hyperuricemia. Autosomal dominant inheritance. Familial juvenile hyperuricemic nephropathy /Medullary cystic Kidney disease

Screening for mutations in the UMOD gene The coding region of the UMOD gene was directly sequenced and a heterozygous missense mutation was found in exon 7. The c. 1463G>A (p.Gly488Asp) allele is a novel mutation and found to co-segregate with the disease in the pedigree. Familial juvenile hyperuricemic nephropathy

Uromodulin (UMOD) mutations cause autosomal dominant tubulo-interstitial nephropaties that are included in the group of cystic kidney diseases : familial juvenile hyperuricemic nephropathy (FJHN) medullary cystic kidney disease nephropathy (MCKD Familial juvenile hyperuricemic nephropathy

This complex is clinically characterized by: alteration of urine concentration hyperuricemia, tubulo-interstitial fibrosis, cortico-medullar cysts renal failure. Gout and hyperuricaemia suggests FJHN Cysts on ultra-sound favours MCKD. Familial juvenile hyperuricemic nephropathy

Mutant uromodulin is retained in the endoplasmic reticulum and cellular trafficking is delayed, leading to reduced uromodulin secretion into urine. Uromodulin associated renal diseases

↓ Na+/K+/ 2 Cl- HyperuricemiaHypertension ↓ Fr Excr UA TALH (ER) Uromodulin Acumulation ↓ / ø urine Uromodulin ↑ Reabs. Na+ e UA Tubular atrophy Interstitial fibrosis Mutant Uromodulin Toxicity ? + APOPTOSIS ? ↓ VLEC Uromodulin associated renal diseases

It is important that physicians consider the diagnosis of FJHN in patients with a family history of hyperuricemia, hypertension associated with renal dysfunction, even if the patient has only mild renal impairment. Uromodulin associated renal diseases

Equate diagnostic: AD familial CRD Interstitial nephritis Irrelevant urinary sediment Ø Proteinuria Early hyperuricemia To confirm diagnosis: Hystology: LM ; EM; IHC Genetic tests Uromodulin associated renal diseases

Pathologic findings in patients with UMOD mutations: Tubular atrophy and interstitial fibrosis. Tubular basement membrane thickening and lamellation. Tubular or glomerular cysts (rare). Inclusions in the cells of TALH (appear as ER inclusions on EM). Dense intracellular UMOD inclusions in the cells of TALH ( by IHC). Uromodulin associated renal diseases

In patients with a poor history, inactive urine sediment and evidence of interstitial nephropathy, it is mandatory to look at the cells of TALH and distal tubules searching for abnormal inclusions by LM and EM. Its evidence implies that UMOD imunohistochemical staining must be done to confirm the composition. Uromodulin associated renal diseases