Frasier Syndrome Terence Cook Imperial College London Kensington, London, United Kingdom

Clinical History The patient was a female referred at age 7 for the investigation of asymptomatic proteinuria initially diagnosed following a history of abdominal pain. She was one of 4 children and all her siblings were well. The only family history of note was that her mother had persistent microscopic haematuria. The patient had no urinary symptoms and she had a normal renal ultrasound. On examination her height was between the 75th and 90th centile and her weight on the 75th centile for her age. Blood pressure was 106/64 mmHg. Urinalysis showed 3+ proteinuria and 3+ haematuria but no red blood cells or casts were seen on urine microsocopy. Urine protein was 2.5g/24 h. Her urinary proteinuria persisted and so she was admitted for a renal biopsy. Her laboratory results at that time were as follows: Hb 13.6 g/dL WBC 6 x 109 per litre C3, C4 normal Creatinine 56 micromol/l (0.49 mg/dL) GFR 96 ml/min/1.6 m2 Albumin 35 g/l ANCA negative IgG 8.2 g/l, IgA 1.8 g/l, IgM 0.7 g/l (all normal) Slide 1 Click to view with ImageScope Click to view with a Web-Based Viewer Slide 2 Click to view with ImageScope Click to view with a Web-Based Viewer Slide 3 Click to view with ImageScope Click to view with a Web-Based Viewer Slide 4 Click to view with ImageScope Click to view with a Web-Based Viewer Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 IgA Figure 9 IgM Figure 10 C1q Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Renal biopsy #1. Representative light microscopy and EM is shown in Powerpoint slides. Immunoperoxidase staining showed segmental mesangial IgM+, C1q+ She was started on enalapril. Her proteinuria persisted and at age 10 was 2.2 g/24h and so the dose of enalapril was increased. At age 11 her GFR had decreased to 74 ml/min/1.6 m2 and Renal biopsy #2 was performed At age 13 her weight was 51.9 kg and height 163.5cm. BP 106/78 mmHg. GFR 52 ml/min/1.6 m2. Her family were very anxious that her GFR had continued to decline and concerned about the effect of her renal failure on her general health. Her mother commented that her periods had not yet started and wondered if this was due to the renal impairment and whether a special diet was needed. Renal biopsy #3 was performed. Renal Biopsy Interpretation Biopsy #1: The biopsy contained 49 glomeruli most of which were normal. Five had prominent areas of increased matrix and increased cellularity and in 2 there were adhesions to Bowman's space. There were several small foci of tubular atrophy and there were collections of foam cells in the interstitium. Immunoperoxidase staining on paraffin sections showed some segmental mesangial IgM+ and C1q+. On electron microscopy the glomerular basement membrane appeared slightly thin in many areas. In other places there was some thickening but no basket weave pattern was seen. There were some focal electron dense 'deposits' in mesangial areas. Podocytes showed segmental foot process effacement The biopsy was interpreted as 'not diagnostic'. It was suggested that there were some features raising the possibility of hereditary nephropathy but that there was also possibly a focal immune complex glomerulonephritis. Biopsy #2: The biopsy contained 20 glomeruli of which 3 showed global sclerosis. Two showed tuft collapse and periglomerular fibrosis and the rest showed mild mesangial hypercellularity. Six showed segmental areas of sclerosis with hypercellularity in the sclerotic areas. Tubular atrophy was estimated at 10% and again foam cells were seen in the interstitium. Immunoperoxidase staining of paraffin sections showed mesangial IgA+, IgM++, C1q++. On electron microscopy there were some large areas of electron density in the mesangium and occasional interamembranous deposits. The biopsy was interpreted as most likely IgA nephropathy with segmental scarring. There was said to be no evidence to suggest hereditary nephropathy Biopsy #3: The biopsy contained 22 glomeruli of which 9 showed global sclerosis. The others showed variable changes with some showing a slight increase in mesangial cells and matrix while others showed a more marked increase. Four had segmental areas of sclerosis with adhesions to Bowman's capsule. There was about 20% tubular atrophy. There were widespread collections of foam cells. Immunoperoxidase staining on paraffin sections showed mesangial IgM++/+++ and C3+. On electron microscopy the capillary basement membrane appeared thin in areas while in other areas there was thickening with possible lamellation. There was variable mesangial matrix increase. In more scarred glomerular segments there was accumulation of electron dense material within basement membranes and mesangium. The biopsy was interpreted as showing focal and segmental glomerulosclerosis suggestive of some form of hereditary nephropathy As noted above her mother had been very concerned that she had not reached puberty and therefore she was assessed by an endocrinologist. She was noted to have no breast development and only scanty pubic hair. Blood was sent for measurement of FSH and LH. FSH was >200U/L (normal 3.0-11.0) and LH was 141 (3.0-12.0) consistent with ovarian failure. Her karyotype was 46,XY. On ultrasound she had a small uterus and small ovaries were identifiable. Subsequently WT1 gene analysis showed a mutation consistent with Frasier syndrome. Discussion This is a case of a patient with persistent non-nephrotic proteinuria and progressive focal and segmental glomerulosclerosis. The EM appearances were difficult to interpret and included thin and thick areas of the basement membrane, mesangial expansion and areas of electron density in the mesangium and glomerular basement membrane. In the second biopsy, but not in the other two, there was some scanty IgA which led at that time to a diagnosis of IgA nephropathy. However, on both the first and third biopsies the suggestion had been raised that there might be a genetic cause. Genetic causes of FSGS include those shown below Autosomal recessive NPHS1 mutations - nephron NPHS2 mutation - podocin NPHS3 mutation - phospholipase C epsilon-1 LAMB2 mutation - laminin β2 Autosomal dominant Localized to 11q21-22 ACTN4 mutations - α-actinin-4 TRPC6 mutations CD2AP mutations Syndromic FSGS WT1 mutations Diffuse mesangial sclerosis Denys-Drash syndrome Frasier syndrome Nail-patella syndrome Alport's syndrome Mitochondrial DNA mutations. WT1 is a zinc finger transcription factor that plays a major role in kidney and gonad development and the maintenance of podocyte function [1]. There are 3 well-defined syndromes associated with WT1 mutations [2]. Diffuse mesangial sclerosis (DMS) and Denys-Drash syndrome show similar glomerular pathology with progressive accumulation of mesangial matrix and progression to renal failure in the first few years of life. Frasier syndrome comprises male pseudohermaphroditism (XY chromosomes, female external genitalia and streak ovaries), progressive nephropathy and ovarian gonadoblastoma [3, 4]. WT1 is composed of 10 exons. Alternative splicing generates four isoforms that are expressed in stable and definite proportions during development and throughout life: the fifth exon may or may not be present and an alternative splice site in exon 9 allows the addition of three amino acids (KTS) between the third and fourth zinc fingers. Frasier syndrome is caused by mutations in the WT1 donor splice site of intron 9 leading to defective splicing of WT1 [5]. This leads to a reduction in the KTS+ transcript compared with controls. In contrast to the glomerular lesions of Denys-Drash syndrome and DMS the characteristic glomerular change is FSGS. However, it is clear that there is overlap with some patients with the typical intron 9 WT1 mutations having morphological changes of DMS [4]. In addition some patients may present with FSGS but without the typical features of Frasier syndrome [6, 7]. The clinical classification is prognostically important and patients with Frasier syndrome generally have slowly progressive FSGS, a low incidence of Wilms' tumour and a higher risk of gonadal tumours. Most reports of the glomerular changes in Frasier syndrome describe a non-specific FSGS but there are several cases with in which variable thinning and thickening of the basement membrane has been described [7, 8] and in the report by Ito [8] these changes were said to resemble those of Alport's syndrome. References Morrison AA et al. New insights into the function of the Wilms' tumor suppressor gene WT1 in podocytes. Am J Physiol Renal Physiol 295:F12-F17, 2008 Niaudet P and Gubler M-C. WT1 and glomerular diseases. Pediatr Nephrol 21:1653-1660, 2006 Frasier SD et al. Gonadoblastoma associated with pure gonadal dysgenesis in monozygous twins. J Pediatr 64:740-745, 1964 McTaggart SJ et al. Clinical spectrum of Denys-Drash and Frasier syndrome. Pediatr Nephrol 16:335-339, 2001 Barbaux S. Donor splice-site mutations in WT1 are responsible for Frasier syndrome. Nature Genetics 17:467-470, 1997 Denamur E. et al. WT1 splice-site mutations are rarely associated with primary steroid-resistent focal and segmental glomerulosclerosis. Kidney Int 57:1868-1872, 2000 Aucella F et al. WT1mutations in nephrotic syndrome revisited. High prevalence in young girls,associations and renal phenotypes. Pediatr Nephrol 21:1393-1398, 2006 Ito S et al. Alport syndrome-like basement membrane changes in Frasier syndrome: an electron microscopy study. Am J Kidney Dis. 41:1110-1115, 2003