Intermittent or daily administration of 1-alpha calcidol for nephrectomised infants on peritoneal dialysis?

Secondary hyperparathyroidism and renal osteodystrophy are major problems in patients with end-stage renal failure and may result in poor growth in children on dialysis. Whether vitamin D sterols should be given intermittently or daily remains a controversial issue. We studied 16 bilaterally nephrectomised infants with congenital nephrosis of the Finnish type (median age 0.54 years), all on peritoneal dialysis. Nine of them were receiving intermittent 1-alpha calcidol therapy and seven daily 1-alpha calcidol therapy. The target serum parathyroid hormone (PTH) level was 2-3 times the upper limit of normal (ULN). There were no statistically significant differences in PTH values between the groups (1.7-times vs 0.5-times the ULN at 3 months and 3.1-times vs 3.4-times the ULN at 6 months, respectively). The required weekly doses of 1-alpha calcidol were low, and there were no significant differences between the intermittent and daily groups (0.06 microg/kg vs 0.04 microg/kg at 3 months and 0.09 microg/kg vs 0.05 microg/kg at 6 months, respectively). The infants on intermittent 1-alpha calcidol showed significant catch-up growth during dialysis after nephrectomy relative to the infants on daily 1-alpha calcidol (-1.6 SD to -0.7 SD vs -1.4 SD to -1.0 SD, respectively; P < 0.05). Our results indicate that either intermittent or daily vitamin D analogue therapy, if started early, will prevent secondary hyperparathyroidism equally well in children on peritoneal dialysis (PD), but intermittent therapy might be more favourable for growth.

Congenital nephrosis, mesangial sclerosis, and distinct eye abnormalities with microcoria: an autosomal recessive syndrome

We observed the occurrence of congenital nephrotic syndrome (CNS) and distinct ocular anomalies in two unrelated families. Eleven children from both families presented with a similar course of renal disease starting with nephrotic syndrome and renal failure prenatally or immediately after birth that resulted in death before the age of 2 months. Kidney histopathology showed diffuse mesangial sclerosis (DMS). Clinically obvious eye abnormalities were recognized in six of the eight patients in whom sufficient clinical data were available. Ocular anomalies included enlarged or large appearing corneae in some cases suggesting buphthalmos, and extremely narrow, nonreactive pupils (microcoria). Pathological examination of the eyes of two aborted fetuses revealed a more complex ocular maldevelopment including posterior lenticonus as well as anomalies of cornea and retina. On the basis of these observations and other cases in the literature, we delineate a previously unrecognized distinct entity characterized by congenital nephrotic syndrome, DMS, and eye abnormalities with microcoria as the leading clinical feature. Pedigrees of affected families with parental consanguinity support autosomal recessive inheritance. We propose that this syndrome should be designated microcoria-congenital nephrosis syndrome or Pierson syndrome. Possible overlap with Galloway-Mowat syndrome and relations to other oculo-renal syndromes are discussed.

Human laminin beta2 deficiency causes congenital nephrosis with mesangial sclerosis and distinct eye abnormalities

Congenital nephrotic syndrome (CNS) is clinically and genetically heterogeneous, with mutations in WT1, NPHS1 and NPHS2 accounting for part of cases. We recently delineated a new autosomal recessive entity comprising CNS with diffuse mesangial sclerosis and distinct ocular anomalies with microcoria as the leading clinical feature (Pierson syndrome). On the basis of homozygosity mapping to markers on chromosome 3p14-p22, we identified homozygous or compound heterozygous mutations of LAMB2 in patients from five unrelated families. Most disease-associated alleles were truncating mutations. Using immunohistochemistry and western blotting we could demonstrate that the respective LAMB2 mutations lead to loss of laminin beta2 expression in kidney and other tissues studied. Laminin beta2 is known to be abundantly expressed in the glomerular basement membrane (GBM) where it is thought to play a key role in anchoring as well as differentiation of podocyte foot processes. Lamb2 knockout mice were reported to exhibit congenital nephrosis in association with anomalies of retina and neuromuscular junctions. By studying ocular laminin beta2 expression in unaffected controls, we detected the strongest expression in the intraocular muscles corresponding well to the characteristic hypoplasia of ciliary and pupillary muscles observed in patients. Moreover, we present first clinical evidence of severe impairment of vision and neurodevelopment due to LAMB2 defects. Our current data suggest that human laminin beta2 deficiency is consistently and specifically associated with this particular oculorenal syndrome. In addition, components of the molecular interface between GBM and podocyte foot processes come in the focus as potential candidates for isolated and syndromic CNS.

Proteinuria and prenatal diagnosis of congenital nephrosis in fetal carriers of nephrin gene mutations

High concentrations of alpha-fetoprotein (AFP) are used for prenatal diagnosis of the Finnish type of congenital nephrotic syndrome (NPHS1). We investigated the validity of this test. We retrospectively established fetal NPHS1 genotype and assessed renal pathology in 21 pregnancies that had been terminated because of raised concentrations of AFP in amniotic fluid. 12 fetuses were homozygous and nine were heterozygous (carriers) for NPHS1 mutations. Raised concentrations of AFP and similar proteinuric features in fetal kidneys were seen in both groups, indicating that these signs are unreliable for prenatal diagnosis of congenital nephrosis. We strongly recommend the use of mutation analysis of the NPHS1 gene to confirm the AFP results in prenatal diagnosis of NPHS1.

Congenital nephrosis of the Finnish type: overview of placental pathology and literature review

Congenital nephrosis of the Finnish type (CNF) is a rare, autosomal recessive disorder of glomerular filtration that results in massive proteinuria, edema, and ascites. Although previous studies describe the classic renal lesions characterizing this disorder, there are few documenting in detail the associated placental alterations. In this context, we present a case of CNF with emphasis on the placental pathology and compare our findings to what has been previously reported in the literature. A 36-year-old G2P1 with no significant medical history developed persistently elevated amniotic fluid alpha-fetoprotein in the absence of neural tube defects. Because of a clinical suspicion of CNF, she electively terminated the pregnancy at 19 weeks. Postmortem examination revealed characteristic renal changes, confirmed by electron microscopy, as well as significant placental villous edema. Although the placenta was not enlarged, the villi appeared profoundly hydropic. Extensive cystic vacuolar change was documented in both stem villi and tertiary villi, affecting 95% of the villi present. Since the fetus was not grossly edematous, the placental findings may represent the first sign of systemic hypoproteinemia.

Prenatal diagnosis of congenital nephrosis by in utero kidney biopsy

The diagnosis of congenital nephrosis is difficult during the antepartum period. The combination of an elevated amniotic fluid alpha-fetoprotein, a negative acetylcholinesterase, and a negative ultrasound examination is highly indicative of congenital nephrosis; however, these findings can also be associated with a normal gestation. This is the first report of pathologic confirmation of congenital nephrosis from an in utero fetal kidney biopsy.

Prenatal characteristics of congenital nephrosis: results of a survey

The purpose of this study was to evaluate the prenatal characteristics of congenital nephrosis of the Finnish type (CNF). Patients presenting with elevated maternal serum and/or amniotic fluid alpha-fetoprotein levels, normal ultrasound examinations and normal fetal karyotypes were included. A retrospective cohort study was conducted using questionnaires sent to all board certified clinical geneticists. Perinatal outcome, including histologic verification of CNF, was obtained. Forty index cases met the above criteria. Ten cases ultimately did not have the diagnosis of CNF, with a median MSAFP level of 7.59 MoM (range 2.7-27.64 MoM) and a median AFAFP level of 10.99 MoM (range 1.47-128.6 MoM). In the affected cohort of index pregnancies, the initial median MSAFP level was 14.49 MoM (range 3.1-38.0 MoM); the median AFAFP level was 40.0 MoM (range 2.4-80.9). MSAFP and AFAFP levels may be lower than previously recognized in patients carrying fetuses with CNF. There is significant overlap between the affected and unaffected patients.

Assembly of a 1-Mb restriction-mapped cosmid contig spanning the candidate region for Finnish congenital nephrosis (NPHS1) in 19q13.1

We describe the assembly of a 1-Mb cosmid contig and restriction map spanning the candidate region for Finnish congenital nephrosis (NPHS1) in 19q13.1. The map was constructed from 16 smaller contigs assembled by fingerprinting, a BAC and a PAC clone, and 42 previously unmapped cosmids. In most cases, single-step cosmid walks were sufficient to join two previously assembled contigs, and all but one gap was filled from this cosmid contig library. The remaining gap of about 19 kb was spanned with a single BAC and a single PAC clone. EcoRI mapping of a dense set of overlapping clones validated the assembly of the map and indicated a length of 1040 kb for the contig. This high-resolution clone map provides an ideal resource for gene identification through cDNA selection, exon trapping, and DNA sequencing.

Galloway-Mowat syndrome in Taiwan

We report on two Chinese female infants with multiple congenital anomalies: microcephaly, apparent porencephaly or encephalomalacia, developmental delay, minor facial anomalies, and contractural arachnodactyly. In the first patient, focal glomerulosclerosis was diagnosed histologically by percutaneous renal biopsy due to proteinuria with hematuria. Congenital hypothyroidism presenting with markedly low T3 and T4 was also noted. She died at age 5 months. The second patient had a very similar condition but less severe brain and kidney malformations. A variant of Galloway-Mowat syndrome is suspected.

Congenital nephrosis in low-risk pregnancies

Congenital nephrosis is an autosomal recessive disorder requiring neonatal renal transplant for survival. The postnatal diagnosis rests upon the electron microscopic evaluation of the epithelial foot processes and basal membrane of the glomeruli. The prenatal diagnosis can be suspected in the presence of a positive family history with an amniotic fluid (AF) alpha-fetoprotein level greater than 5 standard deviations (SD) above the population mean accompanied by a negative AF acetylcholinesterase, absent haemoglobin F, and an unremarkable fetal sonographic examination. We reviewed our series of seven cases of congenital nephrosis fulfilling the above criteria; four cases had negative family histories, and in two cases the diagnosis of congenital nephrosis was further supported by the presence of elevated AF albumin concentrations. We conclude that (1) the prenatal diagnosis of congenital nephrosis is feasible in a low-risk population, and (2) an elevated AF albumin concentration may represent an additional marker for the diagnosis of congenital nephrosis, even though false-negative results have been reported.

Congenital nephrosis of the Finnish type (CNF): matrix components of the glomerular basement membranes and of cultured mesangial cells

Congenital nephrosis of the Finnish type (CNF) is a hereditary renal disease of unknown aetiology manifested by massive proteinuria of the newborn and unresponsive to any treatment. In this study kidney samples and cultured glomerular mesangial cells from five patients with CNF were studied by indirect immunofluorescence microscopy for the presence and location of major basement membrane matrix (GBM) components. Histological changes of glomeruli ranging from mild thickening of basement membranes to total obliteration and sclerosis were seen. Notably, thickening of the subepithelial layer of Bowman's capsules was regularly seen along with hypercellularity at the juxtaglomerular areas. The matrix components studied (laminin, plasma- and cellular fibronectin, type IV collagen, including the NC-1, alpha-1 and alpha-3 chains, heparan sulphate proteoglycan (HSPG) core protein, thrombospondin) were characteristically seen within the glomeruli. Local thickenings alternating with total loss of epitopes along the GBM were seen, especially with anti-type IV collagen and anti-HSPG antibodies. Sera from CNF patients after transplantation failed to show antibodies against GBM structures in immunofluorescence microscopy, suggesting that no missing epitopes of GBM are introduced with the transplant kidney. Cultured mesangial cells of CNF glomeruli also showed continued in vitro production of the matrix components and their incorporation into the matrix underneath the cell layer.

Changes in biological activity and immunoreactive mass of lipoprotein lipase in congenital nephrosis: relationship to hypertriglyceridaemia

The major lipid disturbance in children with congenital nephrosis of the Finnish type (CNF) is hypertriglyceridaemia. To determine whether or not hypertriglyceridaemia is caused by defective triglyceride catabolism, we measured lipoprotein lipase (LPL) activities and masses at various stages of the disease. At age 3 months in CNF both LPL activity and mass were decreased, but a close positive correlation between these parameters similar to that in controls was observed. At age 9 months both LPL activity and mass were even lower. At that time a significant positive correlation (r = 0.72, P < 0.05) between LPL activities and albumin concentrations and significant negative correlations between plasma free fatty acid (FFA) concentrations and LPL activities (r = -0.72, P < 0.05) and between plasma FFA concentrations and serum albumin concentrations (r = -0.73, P < 0.05) were observed, suggesting that low albumin concentrations result in increase of FFA levels, which could interfere with a normal LPL function at the endothelial surface. On dialysis after nephrectomy, LPL activities and masses increased. At age 3 and 9 months apoprotein C-II (apo C-II) and apoprotein C-III (apo C-III) levels were not decreased although apoproteins were being lost into the urine. On dialysis the mean ratio of apo C-II/C-III was significantly lower than the mean in controls (P < 0.001). We conclude that impaired function of LPL seems to be the major cause of hypertriglyceridaemia and disintegrity of the VLDL-IDL-LDL delipidation cascade in children with CNF.

Prenatal diagnosis of congenital nephrosis of the Finnish type (CNF) in the second trimester

Congenital nephrosis of the Finnish type is an hereditary, autosomal recessive disease which leads to death in early infancy. This is a case report concerning an affected fetus with legal interruption in the 24th week of gestation on the basis of certain sonographic changes in the fetal kidneys and changes in the protein profile in amniotic fluid, which were consistent with nephrotic damage of the kidneys. Light and electron microscopy showed evidence of CNF, i.e. increase of mesangial matrix and cells in glomeruli, dilated tubular segments, and effaced and plumb foot-processes of the glomerular epithelial cells. Antenatal diagnosis of CNF therefore seems feasible in the second trimester of gestation by means of AFP determinations in maternal serum and amniotic fluid as well as by using sonographic criteria and determination of proteins in amniotic fluid.

Congenital nephrosis: detection of index cases through maternal serum alpha-fetoprotein screening

Congenital nephrosis is an autosomal recessive disorder with an incidence of 1 in 8000 in Finland, but it is quite rare in non-Finnish populations. In families known to be at risk, prenatal detection is possible by means of maternal serum and/or amniotic fluid alpha-fetoprotein levels. We report the antenatal diagnosis of four cases of congenital nephrosis, three of which were index cases, through maternal serum alpha-fetoprotein screening. The diagnosis was confirmed at birth in two infants. Two patients elected to terminate their pregnancies, and the diagnoses were confirmed pathologically (obliteration of foot processes on electron microscopy of fetal glomeruli) in both. In cases of elevated maternal serum alpha-fetoprotein, with unexplained and marked elevations of amniotic fluid alpha-fetoprotein and normal acetylcholinesterase levels, the diagnosis of congenital nephrosis must be considered regardless of ethnic origin.

Rare causes of elevated maternal serum alpha-fetoprotein. A report of three cases

Three rare conditions--amniotic band disruption sequence, placental chorioangioma and congenital nephrosis--were diagnosed in midtrimester because of elevated maternal serum alpha-fetoprotein. The diagnosis is important for genetic counseling and obstetric follow-up.

Congenital nephrosis as a cause of elevated alpha-fetoprotein

Two cases of congenital nephrosis were detected through routine maternal serum alpha-fetoprotein (MSAFP) screening of 95,135 patients. No other cases of congenital nephrosis from this group were reported, resulting in an incidence of approximately one in 47,500 in this low-risk population. In both of these cases, similar to other reported cases of congenital nephrosis having MSAFP screening, the protein concentrations were greater than or equal to 10 multiples of the median (MOM). Therefore, in the case of an MSAFP over 10 MOM and a normal ultrasound examination, congenital nephrosis should be included in counseling regarding the possibility of undetected malformations. Furthermore, in the case of a pregnancy with elevated amniotic fluid AFP with negative acetylcholinesterase and normal ultrasound, the possibility of congenital nephrosis should be mentioned, regardless of family history or ancestry. When a pregnancy is terminated because of these biochemical findings, special and immediate attention to the fetal kidneys using electron microscopy is necessary to evaluate properly the possibility of congenital nephrosis.

The role of ultrasonography and amniocentesis in the evaluation of pregnancies at risk for neural tube defects

To assess the relative efficacy of amniocentesis versus targeted (detailed) ultrasonography, 225 patients referred because of an elevated maternal serum alpha-fetoprotein level (79.6%) or a family history of neural tube defect (20.4%) were evaluated. Ultrasonographic examination alone detected all 26 fetal abnormalities (11 cases of anencephaly, 10 cases of open spina bifida, and five other anomalies). Twenty-eight patients declined amniocentesis; all had normal pregnancy outcomes. Of the 167 patients with apparently normal fetal anatomy by sonography, seven had elevated alpha-fetoprotein levels but no acetylcholinesterase in the amniotic fluid. Six of these pregnancies resulted in normal infants; one infant had congenital nephrosis. The remaining 160 patients had normal sonograms with normal amniotic fluid alpha-fetoprotein levels and no fetal malformations at delivery. Although these results suggest that targeted ultrasonography by experienced personnel is a reasonable alternative to amniocentesis in evaluations for neural tube defects, the availability, cost-effectiveness, and diagnostic accuracy of this approach must be well documented in large prospective studies.

Accumulation of laminin and type IV collagen in the kidney in congenital nephrosis

The aim of this study was to evaluate qualitatively the occurrence of the basement membrane proteins laminin and type IV collagen in the kidneys of ten infants with congenital nephrotic syndrome of the Finnish type (CNF) aged from 3 to 23 months and to compare the results with those for age-matched controls. A slow accumulation of basement membrane (BM) material occurred in the glomerular mesangium, the peripheral capillaries, around atrophied tubules, and the renal vessels in the course of the disease. The staining pattern of accumulated material depended on the duration of the disease and subsequent renal parenchymal damage. Young CNF patients with slight morphological changes in the kidney had only focal and minimal increases in the amounts of mesangial matrix, but as the disease advanced, so the BMs of the glomerular capillaries, renal arteries, and atrophied tubules also became involved and were thicker than normal. The staining reaction was in all patients similar with antibodies against the fragment P1 of laminin and the 7-S domain of type IV collagen. The accumulation of BM material in CNF kidneys is regarded as a secondary phenomenon induced by an unknown pathogenetic defect in the metabolism of some BM component.

Antenatal screening for congenital nephrosis in Finland by maternal serum alpha-fetoprotein

In the Kuopio and North-Karelia districts of Finland 10724 pregnancies were screened for congenital nephrosis by maternal serum alpha-fetoprotein (AFP) measurement. Outcome was known for 10504 (98%) pregnancies, of which 509 (4 X 8%) had a serum AFP level greater than or equal to 2 X 5 multiples of the normal median (MoM) at 15-18 weeks gestation. After exclusion of those women who had a normal serum AFP level (less than 2 X 5 MoM) in a second sample, 'wrong dates' or multiple pregnancy, 267 (2 X 5%) remained with a high serum AFP level. Amniocentesis was carried out in 225 (2 X 1%) and 16 women had an amniotic fluid AFP level greater than 10 SD above the normal mean. In this group there were six fetuses with congenital nephrosis (four confirmed and two suspected), six other serious malformations (including an intrauterine death) and four without obvious abnormality. In the 98% pregnancies followed up there were no infants with congenital nephrosis that had been missed. Babies with congenital nephrosis require permanent hospitalization and have a mean survival of 8 months. In Finland, within certain areas, the birth prevalence is as high as 1 in 2600 per year. In such areas maternal serum AFP measurement appears to be a useful method of screening for congenital nephrosis. The service was also well accepted since 94% of the women with raised serum AFP levels wished to be screened again in a future pregnancy.

Pachygyria and congenital nephrosis disorder of migration and neuronal orientation

A case of pachygyria with associated nephrosis has been studied. Several microscopic abnormalities have been identified: cytoarchitectonic disorders including neuronal ectopies in the molecular layer and in the meninges, improperly oriented neurons shown with Golgi stain, fetal aspect of inferior olives. The mechanism of the disorder of migration and neuronal and dendritic orientation are discussed. The significance of the association of microcephaly and nephrosis is also reviewed in light of recent literature.

Growth failure due to uremia and congenital nephrosis: growth enhancement by aggressive nutritional therapy

The metabolic and nutritional effects of long-term parenteral and enteral nutrition were studied in two infants and one child with severe growth failure due to chronic renal failure (two patients) and congenital nephrosis (one patient). Six periods of treatment were analyzed. Both the parenteral nutrition and continuous enteral nutrition were found efficient in enhancing growth and correcting the metabolic abnormalities of uremia. The beneficial effects of this intensive nutrition were smaller in congenital nephrosis, although growth accelerated. Nitrogen balance studies confirmed effective nutrient utilization. The serum levels of calcium and phosphate were normalized as anabolism was achieved in the uremia. In fact, the rapid development of severe hypophosphatemia in one of the patients proved that the "fatal hyperalimentation syndrome" appears to be a specific threat in parenteral nutrition applied in uremia.

Renal pathology of fetal congenital nephrosis

In 15 fetuses with congenital nephrosis, distinct colloid-filled cystic tubular dilations were seen scattered in the renal cortex. Similar structures were not present in the controls. It is suggested that these structures are pathognomonic of congenital nephrosis in the fetus and make diagnosis possible even without electron microscopy.

Gel electrophoresis of amniotic fluid acetylcholinesterase as an aid to the prenatal diagnosis of fetal defects

The presence of absence of a specific acetylcholinesterase (AChE) band was determined by polyacrylamide gel electrophoresis on 272 second trimester amniotic fluid samples. The AChE band was absent from 176 normal samples, including seven which had been scored as false positives by alphafetoprotein (AFP) assay. It was present in all 30 samples from open neural tube defects, of which four had been scored as false negatives by AFP assay. In remaining 66 pregnancies with abnormal outcome, an AChE band was in general present when AFP was raised and absent when it was normal. However, all six cases of congenital nephrosis had raised AFP and no AChE band, while two of 30 pregnancies ending in spontaneous abortion had an AChE band and normal AFP. These results suggest that AChE electrophoresis is a valuable confirmatory technique for the early prenatal diagnosis of fetal abnormalities.

Pregnancy specific beta 1-glycoprotein and human chorionic gonadotrophin levels n amniotic fluid and maternal serum in the first half of pregnancy

Pregnancy-specific beta 1-glycoprotein (PSBG) and chorionic gonadotrophin (HCG) were measured by radioimmunoassay in the amniotic fluid of 99 normal pregnancies, 19 pregnancies of women at risk of having another child with congenital nephrosis and 8 pregnancies in which the fetus had a neural tube defect. Maternal serum PSBG and HCG levels were estimated in 52 normal pregnancies and 15 pregnancies at risk for congenital nephrosis. Both amniotic fluid and maternal serum PSBG levels increased in either compartment after 14th week of pregnancy. There was a positive correlation between maternal serum and amniotic fluid PSBG concentrations (P less than 0.001), between maternal serum and amniotic fluid HCG concentrations (P less than 0.001), and between the amniotic fluid PSBG and HCG levels (P less than 0.05) at a given week of pregnancy (wk 15). On average the maternal serum PSBG level was 20-50 times and the HCG level 2-3 times the amniotic fluid level of normal pregnancies. In cases with a neural tube defect the amniotic fluid PSBG and HCG values were similar to those in normal pregnancy. In congenital nephrosis the amniotic fluid HCG concentration was higher than normal at 15-16 weeks of gestation (P less than 0.05), whereas the amniotic fluid PSBG concentration was normal. Thus, placental pathology in congenital nephrosis appears to be reflected as an increased amniotic fluid concentration of HCG in the second trimester.

Prenatal diagnosis of congenital nephrosis in 23 high-risk families

The efficacy of maternal serum and amniotic fluid alpha-fetoprotein (AFP) estimation for the prenatal detection of congenital nephrosis was assessed in 23 pregnancies of couples with a previously affected child. At 15 to 18 weeks' gestation, amniotic fluid AFP concentration was elevated in seven of 23 cases, and maternal serum AFP level in five of these. Legal abortion was carried out at 18 to 19 weeks in all those cases where he amniotic fluid AFP concentration was abnormally high, and in all cases the fetus was found to be affected. The diagnosis of intrauterine congenital nephrosis was obvious by electron microscopic examination of the fetal kidney, but not by light microscopy. The child was born without congenital nephrosis in all 16 cases where amniotic fluid AFP level was normal, and in 16 of 18 cases (89%) where maternal serum AFP concentration was normal. Thus, the amniotic fluid AFP assay is more reliable and is recommended whenever congenital nephrosis is suspected on the basis of family history.

Fetal proteinuria in diagnosis of congenital nephrosis detected by raised alpha-fetoprotein in maternal serum

High concentrations of alpha-fetoprotein (alpha-FP) were found at 14, 19, and 21 weeks gestation in the serum of a woman with a history of unexplained fetal death in her previous pregnancies. The alpha-FP concentration of the liquor also was high at 21 weeks and the pregnancy was terminated. Though the fetus was macroscopically normal, measurement of albumin, alpha-FP, IgG, and alpha2-macroglobulin in the fetal urine showed a selective proteinuria, and congenital nephrosis was diagnosed after examination of the fetal kidneys by electron microscopy. Possibly some fetuses reported to be "false-positive for neural tube defect" may have had renal lesions of this nature. Examination of fetal urine may be the simplest initial diagnostic procedure in any future case.

Mechanisms by which amniotic-fluid alpha-fetoprotein may be increased in fetal abnormalities

Assuming that urination is the principle route by which alpha-fetoprotein (A.F.P.) passes into the amniotic fluid from the normal fetus, and that A.F.P. is mainly degraded by a process of fetal swallowing and digestion, 4 possible mechanisms by which amniotic-fluid A.F.P. is increased by fetal abnormalities are postulated.(1) Amniotic-fluid A.F.P. is increased in open neural-tube defects by leakage of A.F.P. from fetal serum and cerebrospinal fluid.(2) In exomphalos exposure of blood-vessels in the extruding viscera permits transudation of A.F.P. into the amniotic fluid.(3) In nephrosis, fetal proteinuria increases amniotic-fluid A.F.P.(4) Impaired fetal swallowing or digestion would account for increased amniotic-fluid A.F.P. in congenital malformations of the orogastrointestinal tract.

Alpha-fetoprotein in antenatal diagnosis of congenital nephrosis

Alpha-fetoprotein (A.F.P,) levels were found to ge significantly raised in maternal serum and amniotic-fluid samples form the 16th and 18th weeks of gestation in a woman with an apparently normal fetus but with histological evidence of congenital nephrosis of the Finnish type. Increased concentrations of A.F.P. in early pregnancy with a living fetus are therefore not specific for neural-tube defects; More likely they result from the fetal circulation. Extended investigations, including kidney morphology, should be done in cases of apparent false-positive A.F.P. tests.