Three cases of late-onset oligomeganephronia

Pathological and clinical characteristics of late-onset oligomeganephronia based on a histomorphometric study

BACKGROUND

Late-onset oligomeganephronia (OMN) is a rare chronic kidney disease and has no quantitative criteria for diagnosis yet. The current study aimed to explore its clinicopathological features by histomorphometric analysis.

METHODS

We retrospectively re-reviewed all patients with enlarged and sparse glomeruli by light microscopy at Peking University First Hospital from 2012 to 2021, excluding those with any factor known to contribute to similar changes. Age- and sex-matched patients with thin basement membrane nephropathy were selected as control to establish the cut-off values for glomerulomegaly and rarity. Late-onset OMN cases were then confirmed and the clinicopathological characteristics were summarized.

RESULTS

Mean diameter and density of cortical glomeruli in control was 156.53 ± 27.50 μm and 4.07 ± 0.63 /mm², giving a lower limit of 211.53 μm for glomerulomegaly and an upper of 2.81 /mm² for rarity. Seven adults of three females and four males were finally diagnosed as late-onset OMN with a mean age of 26.57 years. They showed mild to moderate proteinuria and/or renal dysfunction at biopsy with the mean proteinuria, serum creatinine (Scr) level, and estimated glomerular filtration rate of 0.50 g/d (0.10-0.95 g/d), 140.9 µmol/L (95.1-227.1 µmol/L), and 58.7 mL/min/1.73m² (21.3-98.0 mL/min/1.73m²), respectively. Four patients (57.1%) had normal Scr at diagnosis. Six patients with available data showed renal tubular injury with increased urinary microalbumin in all, elevated N-acetyl-β-glucosaminidase in two, and elevated α1 microglobulin in five. Kidney size was normal or slightly reduced. The mean density and glomerular diameter of the seven cases was 0.86 mm² (0.55-1.41 /mm²) and 229.73 μm (211.88-260.66 μm). Segmental glomerular sclerosis was observed in six (85.7%) with four (66.7%) of perihilar type. Proximal tubule dilation was observed in all, focal to diffuse, lining with enlarged epithelial cells. The mean foot process width was 634.02 nm, wider than 472.54 nm of the control (P = 0.0002).

CONCLUSION

Late-onset OMN should be considered a special entity with relatively slow clinical progress characterized by hypertrophy of the sparsely distributed nephron.

A Case Report and Literature Review of Oligomeganephronia

A 23-year-old woman was admitted to the hospital with proteinuria and mildly elevated creatinine, and a renal biopsy confirmed the diagnosis of oligomeganephronia (OMN). OMN is an extremely rare bilateral renal hypoplastic disease, and its diagnosis mainly relies on the pathological results obtained from renal biopsy. At present, there is no effective treatment for OMN. Here, we report a case with mild renal insufficiency and proteinuria as the main symptom and present a summary of the clinical characteristics of ON along with a review of the literature on OMN.

PAX2 Mutation-Related Oligomeganephronia in a Young Adult Patient

Oligomeganephronic hypoplasia, commonly referred to as oligomeganephronia (OMN), is a rare pediatric disorder characterized by small kidneys. Histologically a paucity of nephrons is observed which show compensatory enlargement. Hyperfiltration injury leads to end-stage kidney disease. Here we report a 23-year-old Caucasian female patient who presented with a 7-year history of nonnephrotic proteinuria, slow worsening of renal function, normal-sized kidneys, normal blood pressure, healthy weight, and normoglycemia. Evaluation of a kidney biopsy specimen revealed sparsely distributed and markedly enlarged glomeruli (glomerular density 0.63/mm², glomerular diameter 268 µm), focal segmental glomerulosclerosis (FSGS), and 70% effacement of the foot processes. The glomerular basement membrane was normal (mean thickness 285 nm). The genetic analysis of 19 genes known to cause FSGS identified a heterozygous de novo nonsense mutation of PAX2 in exon 4 (NM_003990.3:c.430C>T and NP_003981.2:p.Gln144Ter). Clinical investigations ruled out optic nerve coloboma, hearing loss, and vesicoureteral reflux. Magnetic resonance imaging of the urogenital tract found the uterus to be bicornuate. Based on these data, OMN in nonhypoplastic kidneys and adaptive FSGS related to PAX2 mutation was diagnosed. Her kidney function worsened during the 30-month follow-up (last visit: eGFR-EPI 32 mL/min/1.73 m²) despite angiotensin-converting enzyme inhibitor treatment. To our best knowledge, our patient is the seventh in the English-language literature with a biopsy diagnosis of OMN in an adult, the first observed with normal-sized kidneys, and the first in whom a specific etiologic genetic diagnosis was established. Nonsense PAX2 mutations between the paired domain and the octapeptide domain appear to manifest in renal-limited phenotype.

Secondary focal segmental glomerulosclerosis in an adolescent born with a very low birth weight

A 17-year-old man presented with a decreased renal function (creatinine clearance 66.0 ml/min/1.73 m2) and proteinuria (1.25 g/24 hrs). He was born weighing 1,065 g 26 weeks of pregnancy. He was mildly overweight (BMI 26.9 kg/m2) due to an increased weight gain (10 kg) over the past year. Renal biopsy showed perihilar sclerosing lesions in three of eleven glomeruli, low glomerular density, enlarged glomeruli, and limited fusions of foot processes, thus indicating secondary focal segmental glomerulosclerosis (FSGS). We speculated that the patient's overweight status may have caused a worsening of glomerular hyperfiltration due to the fewer number of nephrons leading to the development of secondary FSGS.

Oligomeganephronia in an adult without end stage renal failure

A 23 year-old male was investigated for hypertension, moderate renal insufficiency, persistent proteinuria and bilateral small kidneys. The renal pathological features were diagnostic with greatly enlarged glomeruli (the mean diameter was 325 μm, which was approximately two times larger than normal glomeruli), indicating oligomeganephronia (OMN). He also showed malrotated kidneys, expanded extrarenal pelvis, and hearing loss. Thus, these clinical and pathological features aided in diagnosing the renal disorder as OMN. This is a very rare case of OMN, which did not advance to end-stage renal failure as an adult. We believe that multiple anomalies might be suggestive findings of OMN in patients, such as renal insufficiency, persistent proteinuria, and bilateral small kidneys.