Glomerular tip changes in childhood minimal change nephropathy

Tip lesion variant of primary focal and segmental glomerulosclerosis: clinicopathological analysis of 20 cases

The glomerular tip lesion (GTL) is a distinctive histopathologic lesion which is regarded as a variant of focal and segmental glomerulosclerosis (FSGS). The prognostic significance of GTL among other FSGS variants has been disputed. In order to define the clinical features and outcome of GTL, we retrospectively reviewed the presenting clinical features, laboratory and biopsy findings and surveillance in our cohort of GTL, which consisted of 20 adults with native kidneys (mean age 46 years) with follow-up data ranging from 3 to 137 months. At presentation, mean urine protein, serum albumin and cholesterol levels were 5.17 g/d, 2.6 g/dL and 312.9 mg/dL, respectively, and none had renal insufficiency. Microscopic hematuria was detected in five patients. At biopsy, glomerular segmental lesions consisted of GTL without perihilar or collapsing lesions. GTL was observed in a variable proportion of glomeruli from 2.6% to 100%. Mesangial proliferation was seen in nine cases, at a moderate degree in two and mild in the rest. Three biopsies showed mild, two showed moderate interstitial fibrosis/tubular atrophy. Eleven patients received steroids alone and eight received sequential therapy with steroids and a cytotoxic agent. At a mean follow-up of 40.6 months, 17 patients (85%) achieved complete remission of nephrotic syndrome, 15% had partial remission. Four of 17 suffered from recurrences. No patient progressed to end-stage renal disease. Serum albumin at diagnosis was the only predictor of a recurrence (p = 0.037). Microscopic hematuria correlated with incomplete remission (p = 0.045). Our study demonstrates a clearly favorable prognosis in patients with FSGS-GTL variant.

Morphologic variants of focal segmental glomerulosclerosis and their significance

Focal segmental glomerulosclerosis (FSGS) comprises a group of clinical-pathologic syndromes characterized by heavy proteinuria and segmental obliteration of glomerular capillaries by extracellular matrix. FSGS lesions display morphologic heterogeneity with respect to their relationship to the glomerular vascular and tubular poles, the presence of capillary collapse, and endocapillary and extracapillary hypercellularity. A working proposal, commonly referred to as the Columbia Classification, distinguishes 5 mutually exclusive morphologic variants: collapsing, tip, cellular, perihilar, and not otherwise specified (NOS), which can be applied to primary and secondary forms of FSGS. Several studies have documented significant differences in baseline clinical characteristics and outcomes between morphologic variants of primary FSGS, supporting that this classification may provide useful prognostic information. The association of certain variants with particular secondary causes of FSGS suggests pathogenetic relevance.

Problems with 'focal segmental glomerulosclerosis'

The term 'focal segmental glomerulosclerosis (FSGS)' has been applied to many different conditions. All classifications of 'FSGS', including those describing 'variants', perpetuate the misconceptions that the entities included have something in common and that the term 'FSGS' has some value. With a rigorous approach to renal biopsies showing segmental lesions, especially with knowledge of clinical circumstances and with detailed analysis of features such as the appearance of lesions and their position within glomeruli, a pathologist can provide information that is clinically more useful than merely the bald diagnosis 'FSGS'. More precise terms should be used. 'Overload changes' can be used to describe the changes seen in reduced renal mass. 'Tip changes' can be seen in many conditions and are not a disease in themselves. 'The glomerular tip lesion as originally defined' means the occurrence of tip changes in otherwise normal glomeruli, in the nephrotic syndrome. 'Early classical segmental sclerosing glomerulopathy' is the combination of tip changes and otherwise abnormal glomeruli, in the nephrotic syndrome. 'Late classical segmental sclerosing glomerulopathy' means segmental lesions at various sites within glomeruli, in the nephrotic syndrome. 'Collapsing glomerulopathy' is distinctive, and its inclusion in classifications emphasises the lack of specificity of 'FSGS'.

Tip variant of focal segmental glomerulosclerosis: outcome and comparison to 'not otherwise specified' variant

BACKGROUND

The clinical significance of focal segmental glomerulosclerosis (FSGS) tip variant remains unclear. With the aim to determine its clinical and histological features, and natural history, we studied our cases of patients with this glomerular lesion.

METHODS

This is a retrospective analysis. All native renal biopsies from patients diagnosed as FSGS, between 1998 and 2006, were revised for cases with tip variant. Glomerulosclerosis (GS), segmental lesions and interstitial fibrosis (IF) were quantified. We analysed clinical and follow-up data and compared with cases of FSGS not otherwise specified (NOS).

RESULTS

In 248 primary FSGS cases, 37 corresponded to tip variant (14.9%). Median age was 17 years (range 1-65); 13 (35.1%) patients were <15 years old, and 56.8% were males. All patients had nephrotic proteinuria. At diagnosis, there were no significant differences for age, renal function and proteinuria between cases with NOS and tip variant. IF, GS and percentage of glomeruli with segmental lesions were higher in NOS than GTL (P < 0.01). At follow-up (n = 25), 15 patients received steroids alone, and 10 steroids and a cytotoxic agent. At a median follow-up of 48.7 months (24.3-86.7), 7 patients (28.0%) progressed to chronic kidney disease (CKD), 4 (16.0%) developed end-stage renal disease (ESRD) and 9 (36.0%) had complete remission. In NOS patients (n = 93), 48 (51.6%) developed CKD (P = 0.04), 20 (21.5%) developed ESRD (P = 0.54%) and 13 (14.0%) had complete remission (P = 0.02).

CONCLUSIONS

Our work does not demonstrate a clearly favourable prognosis in a group of patients with FSGS tip variant. Although in the tip variant there are less chronic renal tissue damage and CKD, and more frequent complete remission of the nephrotic syndrome, there is an important percentage of patients who develop CKD and ESRD.

Focal segmental glomerulosclerosis: a morphologic diagnosis in evolution

CONTEXT

The diagnosis of focal segmental glomerulosclerosis (FSGS) is a descriptive pathologic diagnosis that in certain clinical situations (ie, primary or idiopathic) becomes its own disease. The clinical diversity, varied histology, and nonspecific morphologic features of FSGS all contribute to the complexity and problematic nature in making a pathologic diagnosis of FSGS. The definitions of the disease and of the morphologic features have evolved during the last century.

OBJECTIVE

To review historic and morphologic features of FSGS in order to demonstrate a practical approach in achieving a pathologic diagnosis of FSGS on kidney tissue.

DATA SOURCES

In 2004 a working proposal on the pathologic (morphologic) classification of FSGS was published in an attempt to unify the complexity of diagnosing FSGS, and it has shown to be both reproducible and with unique clinical implications for each defined FSGS variant.

CONCLUSIONS

An accurate diagnosis of FSGS can be challenging. During the last few decades, numerous new scientific discoveries have enriched our knowledge of pathogenetic mechanisms of nephrotic syndrome. Thus, it is expected there will be a need for a further modification to a morphologic classification and that the pathologist's role in diagnosing FSGS will remain in evolution. This review recapitulates the history of the pathologic diagnosis of FSGS and a current morphologic classification, hopefully opening up a discussion for further modifications that reflect the status of knowledge evolving in the 21st century.