Glomerulocystic kidney disease is an uncommon type of cystic renal disease. Roos first described it as an isolated abnormality in 1941 [4
]. However, Taxy and Filmer proposed the term of GCKD in 1976 [1
], which is widely used to describe the characteristic morphological features of dilatation of Bowman's space often without quantitative criteria. Bernstein defined glomerular cyst as dilatation of Bowman's space 2–3 times in the plane of section [2
]. He also considered that the occurrence of glomerular tufts, within atleast 5 % of otherwise identifiable cysts, defines glomerulocystic kidney. However the definition does not exclude the presence of associated tubular dilatation. GCKD can be categorized into five major groups [3
1. Familial GCKD,
2. GCKD associated with heritable diseases such as ADPKD/ARPKD and tuberous sclerosis,
3. Syndromic, non-hereditary GCKD,
4. Sporadic GCKD and
5. Acquired GCKD.
The first group includes autosomal dominantly transmitted GCKD (ADGCKD). The second group comprises of diffusely glomerulocystic kidneys in newborns and young children, many of whom have family histories positive for classical polycystic kidney disease. It also includes sporadic and familial disease in older children and adults. No differences between familial and sporadic cases have been identified, apart from the family histories. The sporadic cases conceivably represent new mutations of the same disease. It also includes glomerulocystic kidneys as major component of heritable syndromes such as tuberous sclerosis, trisomy 13 and others. The third group includes glomerulocystic kidneys as components of diffuse cystic dysplasia and renal-hepatic-pancreatic dysplasia syndrome. The fourth group comprises all the sporadically occurring GCKD. Acquired GCKD (group 5) has been described following hemolytic-uremic syndrome [5
The mechanism of cyst formation in GCKD is poorly understood. Various factors that may be involved in the pathogenesis of GCKD include tubular obstruction due to renal medullary inflammation in neonates, increased intraglomerular pressure when the fetal glomeruli become functional and maternal intake of drugs such as phenacetin during pregnancy [6
]. Baxter et al suggested that GCKD is produced late in gestation, by malformation in nephrogenic zone or tubular obstruction [7
]. Ischemia, an acquired factor, may be involved in the genesis of glomerular cysts and explain sporadic forms observed in adults [8
]. Evidence for the glomerular origin of the cysts was first provided by Baxter. Vernani et al in a study have shown that, the cysts showed negative staining with markers of proximal and distal tubular epithelium, thereby suggesting a glomerular origin of cysts [9
]. Although no microdissection studies were performed in our cases, the morphometric findings also support glomerular origin of GCKD [10
]. Recent studies have also suggested stenosis at glomerulo-tubular junction to be the main cause of glomerular cyst development. However, three-dimensional imaging analysis has excluded stenosis or obstruction at the level of the glomerulo-tubular neck [11
]. Recently, mutation in the hepatocyte nuclear factor-1beta (HNF-1β) gene has been identified in hypoplastic GCKD variant [12
]. The genetic studies could not be carried out in our cases. However there was no history of any cystic disease/or renal function derangement in the siblings in both the families.
Dilatation of the bladder and ureters can be seen with any obstructive lesion of lower urinary tract, but in the megacystic-megaureter syndrome, no anatomic obstruction is present [13
]. Severe vesicoureteric reflux leads to the constant recycling of large volumes of refluxed urine, which in turn results in an enlarged bladder and massively dilated ureters [14
]. There was no evidence of posterior uretheral valves, thus the plausible explanation for megacystic-megaureter in abortus appears to be a functional defect, which must also have contributed partly to development of dysplasia and glomerular cysts. Evidence for such a mechanism derives from experimental ureteral ligation in neonatal animals [15
The above two cases illustrates the sporadic form of GCKD (group 4) occurring in term baby and syndromic, non-heritable GCKD (group 3) in a 17-week abortus according to the above classification. A recent literature review failed to show a link between this rare association of GCKD with TEF, and megacystic-megaureter syndrome. Glomerular cysts are considered to be the basic and predominant lesions of GCKD. No dilatation of tubules is present; the absence of tubular dilatation excludes the diagnosis of ADPKD. Dysplastic elements were noted in the kidney sections of abortus, however were absent in term baby.
In conclusion, the above two cases highlight the rare associations with which this heterogeneous entity is associated.