Genetic and clinical studies in autosomal dominant polycystic kidney disease type 1 (ADPKD1)

TFE3-rearranged nonmelanotic renal PEComa: a case series expanding their phenotypic and fusion landscape

AIMS

A subset of exceptionally rare primary renal perivascular epithelioid cell tumours (PEComas) that harbour Xp11.2 translocation have been reported, but no larger series devoted to this topic have been published.

METHODS AND RESULTS

We describe the clinicopathological and molecular features of 10 renal PEComas, collected from our routine and consultation files. There were five female and five male patients aged 14-65 (median: 32 years). One patient had a history of childhood neuroblastoma, but no patients were known to have a tuberous sclerosis complex or other hereditary disorder. Complete surgical excision was the treatment for all patients. The available follow-up in five patients indicated a favourable outcome in 4/5 cases. Tumour size ranged from 2.8 to 15.2 cm (median, 5.2 cm). Immunohistochemistry revealed consistently strong TFE3 expression in all tumours, whereas PAX8 and keratin cocktails were uniformly negative. Other positive markers included HMB45 (7/9 tumours), CathepsinK (7/9 tumours), and CD117 (KIT) (3/5 tumours). TFE3 rearrangements were detected in 8/9 tumours (by targeted RNA sequencing in seven and by FISH in one). The identified fusion partners included SFPQ (n = 2) and one tumour each with ASPSCR1, ZC3H4, MED15, RBMX, and PRCC. One tumour that lacked TFE3 rearrangement by next-generation sequencing (NGS) and fluorescence in situ hybridization (FISH) revealed a large intrachromosomal deletion involving PKD1 and TSC2 by DNA-based NGS.

CONCLUSION

This study highlights the morphologic and genetic diversity of TFE3-rearranged primary renal PEComas and underlines the value of surrogate TFE3 immunohistochemistry in identifying them. The lack of PAX8 and keratin expression represents the mainstay for distinguishing these tumours from MiTF-associated renal cell carcinomas. In addition, we report rare (ZC3H4, RBMX) and novel (MED15) TFE3 fusion partners in PEComa.

A family with a milder form of adult dominant polycystic kidney disease not linked to the PKD1 (16p) or PKD2 (4q) genes

Autosomal dominant polycystic kidney disease (ADPKD) is a genetically heterogeneous disease. Most families show positive linkage to polymorphic markers around the PKD1 (16p13.3) or PKD2 (4q21-23) loci. The PKD1 and PKD2 genes have been cloned and mutations defined in a number of patients. Several clinical studies have described a milder phenotype for PKD2 patients. More recently, evidence for a third genetic locus has been found in one Portuguese, one French-Canadian, and one Italian family. We identified a Spanish family with negative linkage to the PKD1 and the PKD2 loci. This family showed a very mild clinical phenotype compared to the other forms of ADPKD, including the non-PKD1/non-PKD2 families previously described.

Genetic analysis of 20 families with autosomal dominant adult polycystic kidney disease from South West Thames Region

Twenty families with autosomal dominant polycystic kidney disease from S. W. Thames Region were analysed using markers for chromosome 16p13.3, the site of the common mutation (PKD1). Six families gave a negative lod-score for 3'HVR, the most informative distal marker. This could be explained in four cases by recombination events. Of the two families where this was not an explanation, one, of Italian origin, was unequivocally unlinked for all markers, and the other was more likely to be non-PKD1 than linked to 16p13.3. The Italian family was ascertained through the Blood Pressure Unit, and the other via the Genetic Clinic. No members of either family had ever attended a renal clinic. The remaining 18 families either came via renal clinics, or had at least one member attending such a centre.

Haplotype analysis in autosomal dominant polycystic kidney disease

Haplotype analysis was performed in 35 autosomal dominant polycystic kidney disease (ADPKD) families typed with 13 markers close to the PKD1 locus. The identification of recombinants close to the PKD1 gene on chromosome 16p indicates that PKD1 lies between CMM65 distally and 26-6 proximally. In addition, three unlinked (PKD2) families and two families with potential new mutation were identified.

Evaluation of ultrasonographic diagnostic criteria for autosomal dominant polycystic kidney disease 1

Although ultrasound is commonly used for screening subjects at risk of polycystic kidney disease 1 (PKD1), there has been no evaluation of ultrasonographic diagnostic criteria. We used DNA linkage among subjects from 128 sibships within 18 PKD1 families as the basis for an assessment of ultrasound sensitivity. Positive and negative predictive values were calculated to allow assessment of different diagnostic cut-off points in previously undiagnosed cases. Currently used criteria (bilateral cysts with at least two in one kidney) provided good sensitivity (88.5% at age 15-29 years and 100% at 30 years and above) but performance could be improved by less stringent criteria in subjects aged 15-29 years and more stringent criteria in older family members, in whom simple renal cysts are frequent. The presence of at least two renal cysts (unilateral or bilateral) in individuals at risk and younger than 30 years may be regarded as sufficient to establish a diagnosis; among those aged 30-59 years, the presence of at least two cysts in each kidney may be required, and among those aged 60 years and above, at least four cysts in each kidney should be required.

A family with autosomal dominant polycystic kidney disease not linked to chromosome 16p13.3

A family of Sicilian origin with autosomal dominant polycystic kidney disease (APKD) has been shown to be unlinked to chromosome 16 markers. LOD scores for the polymorphic markers 3'HVR and SM7 flanking the PKD 1 locus, were -1.4 and -2.33 respectively, and theta max was 0.5 for each marker. The clinical phenotype of this family is consistent with that of the other non-linked families with APKD reported in the literature, all outside the United Kingdom, which have a milder progression than those linked to 16p13.3. Assuming that a clinic population represents the most severe forms of a disease and non PKD-1 is a less aggressive phenotype, the degree of genetic heterogeneity for APKD in the population may well be much greater than at present suggested.

Childhood onset autosomal dominant polycystic kidney disease in sibs: clinical picture and recurrence risk. German Working Group on Paediatric Nephrology (Arbeitsgemeinschaft für Pädiatrische Nephrologie

In a systematic study on the clinical picture and genetics of cystic kidneys in children, in association with the German working group on paediatric nephrology (Arbeitsgemeinschaft für Pädiatrische Nephrologie), we have investigated 79 children with early manifestation of autosomal dominant polycystic kidney disease (ADPKD). They belonged to 64 families (64 index patients and 15 affected sibs). Early manifestation was defined in this study as clinical symptoms (hypertension, proteinuria, impaired renal function, palpably enlarged kidneys) occurring before the age of 15 years. In order to estimate the recurrence risk to sibs of a previously diagnosed patient with early manifesting ADPKD, we found that 15 out of a total of 65 sibs of the 64 index patients (45% of the theoretically expected 32.5 gene carriers) showed comparable early manifestation. Another 10 symptom free children were diagnosed sonographically as having ADPKD before the age of 18 years, so that the total number of affected sibs was 25/65 in the study group, representing 76% of the gene carriers. Although the gene in childhood manifesting ADPKD can be transmitted through both sexes, a statistically significant (p < 0.05) maternal predominance was observed (M:F = 23:41). In affected sibs ages of onset, initial presentation, and the development of complications appeared to be similar in the majority of families. Our data indicate a high recurrence risk to sibs for early manifestation of ADPKD which has important implications for genetic counselling and clinical care of affected families and gives clues to the underlying genetic mechanism of childhood onset ADPKD.