childhood cystinuria in newsouthwalescystinuria. of the remaining 43 families, 27 were typei...

Archives of Disease in Childhood, 1979, 54, 676-681

Childhood cystinuria in New South WalesResults in children who were followed up after being detected by urinaryscreening in infancy

ARABELLA SMITH, J. S. YU, AND D. A. BROWN

Health Commission ofNew South Wales, Oliver Latham Laboratory, andRoyal Alexandra Hospitalfor Children, Sydney, Australia

SUMMARY Homozygous cystinuria was diagnosed in 45 children and 19 of their siblings in the course

of routine urine screening of 6-week-old infants in New South Wales. These children were followedfor up to 14 years. During this time there were 5 clinical episodes of renal disease which could beascribed to cystinuria. There was normal mental development in all the children except one. Of 49children over 3 years, 4 had height centiles less than the midparent height centile, while 45 hadheight centiles equal to or above the midparent centiles. Family testing in these 45 cases showed that60% were type I cystinurics, and 35 % were of the mixed or compound type (5 % were not classified).Data from the parents and grandparents showed that renal tract calculi had occurred in 14 of them.This study shows that children with homozygous cystinuria, detected by urinary screening in infancy,rarely have renal symptoms. Mental development was normal as was growth in height. There wasan increased incidence of noncystine stone formation among the relatives of these children. Theincidence of homozygous cystinuria in New South Wales is one in 17 286.

Cystinuria is a disorder ofrenal tubular and intestinaltransport of amino-acids. the main clinical associa-tion being renal calculi formation. Colliss et al. (1963)reported a height deficit in cystinurics compared withthe general population, and Scriver et al. (1970)suggested that mental retardation was an associatedfeature. Many cases of cystinuric stone formers havebeen described, mainly in adults, although in thestudy of Bostrom and Hambraeus (1964) in Swedenthere were 9 children and adolescents, most of whomwere identified by the clinical manifestations ofcalculus disease. We report the results in a group ofchildren with homozygous cystinuria who werefollowed up after being identified by newbornscreening of urine.

Methods

During a 13-year period (1964 to end of 1977), urine

Health Commission of New South Wales, Oliver LathamLaboratory, AustraliaARABELLA SMITH, medical officerD. A. BROWN, scientific officerRoyal Alexandra Hospital for Children, Sydney, Australiaj. s. Yu, medical superintendent

samples from 950 767 6-week-old babies in NewSouth Wales, 85% of the infant population, wereexamined by unidimensional paper chromatography(Wilcken et al., 1973). If this first urine test showedmarkedly raised levels of cystine, lysine, or arginine(ornithine is not well separated by this method) arepeat test was requested. These first two tests wereperformed on urine-soaked blotting paper slips, butif the second test also showed a gross aminoaciduriaconsisting of cystine, lysine, or arginine, a liquidurine specimen was requested. A definitive diagnosisof homozygous cystinuria was made if thistest showed high levels of cystine, lysine, andarginine, the baby usually being 6 months by thisstage.

Children with homozygous cystinuria were seenfor initial assessment and then at least yearly. At eachvisit they were assessed clinically, their generalhealth was assessed, and their parents were alsoquestioned specifically about the occurrence of backache, abdominal pains, renal pain or colic, haema-turia, frequency of micturition, and scalding of urine.They were asked about any medication the child hadreceived, the diet, and details of fluid intake. Heightand weight (without shoes) of the affected children

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Childhood cystinuria in New South Wales 677

were measured as were also the heights and weights ofthe siblings and parents seen at the follow-up.No correction was made for parent's age, all beingunder 40 years of age. The children's height centilesand the midparent height centiles were calculatedusing the tables of Tanner et al. (1970). The parentswere encouraged to bring the whole family to eachvisit and unaffected siblings were also seen severaltimes in most families.Formal IQ testing in these patients was not

routinely done. Achievement of milestones wasrecorded and parents were asked to rate the develop-ment of the child as slower than, the same as, orquicker than that ofunaffected siblings. Children whohad completed at least 2 years of schooling wereassessed by their school reports and their class levelfor the age. If they were in the top class for the agegrade, they were rated as good, if in the middle classas average, and if in the lowest class they were ratedas slow. Their school level was also compared withtheir siblings.The management of the children was the same in

all cases, namely increased fluids to the limit oftolerance. None of the children had been givenurinary alkalinisers, D-penicillamine treatment, orprotein restriction at the time of this report. Fourchildren (from 2 families) were investigated bio-chemically on a number of occasions, but have notbeen seen by us. Information was obtained from thefamily doctor by means of a specific questionnaire,as described above.At each follow up, a sterile midstream specimen of

urine was obtained and this was immediately set upfor microurine analysis by standard methods.Urinary amino-acids were examined at each visit byhigh voltage electrophoresis, cystine was estimatedquantitatively (Rootwelt, 1967), the presence ofexcess arginine confirmed by the Sakaguchi reaction(Smith, 1969), and cystine crystals were sought usingthe method of Hepler (1950). These examinationswere performed on fasting first morning urinespecimens in most patients but in some of the olderones on a 24-hour urine specimen. In 4 cases,urinary amino-acids were estimated on a BeckmanUnichrome amino-acid analyser.Once the patient had reached age 4 or 5, a plain

x-ray of the abdomen was taken to exclude thepresence of a calculus, and this was repeated 2 or 3years later in some of the older patients. A detailedgenetic history was also obtained at the initial visitwith specific questioning about family history ofrenalcalculi, consanguinity, and abortions, as well asabout more general genetic conditions. Urinespecimens from both parents and all siblings weretested in each family; in some families other familymembers were also tested.

Results

Of 950 767 babies tested between the start ofscreening in 1964 and the end of 1977, 45 were foundto have cystinuria, 19 of 89 siblings tested were alsoaffected, giving a total of 64 known cases (Table 1).38 were boys and 26 girls, giving a sex ratio of 0 * 59(P>0 2). Ten of the 19 homozygous siblings wereborn after the propositus and are shown as propositithemselves in the incidence figures and in the dis-cussion of initial urinary test findings. In one family2 affected siblings of the propositus were unliketwins, and in another family with twins, one washomozygous and the other normal. The ages of the64 children are shown in the Figure.

Initial urine testing showed a typical aminoaciduria

Table 1 Siblings of the cystinuric propositi

Propositi Siblings(n = 45)

Homozygous Hetero- Normal Totalzygous*

Boys (n=28) 19-10 18-11 52-33 89-54Girls(n=17) - 9 - 7 -19 -35

*From 16 mixed or compound families.

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Figure Age of 64 homozygous cystinuric patients.The scale for age ranges is not uniform, and changesin scale are shown by a space-for example the 12-14block represents a 3-year period (1964-66), being yearsduring whiich few cases were detected, and >1 blockrepresents a one-year period (1977), a year in whichthere were many cases. The 7 patients, aged at least15 years and born before 1964, were found when theirfamilies were tested. Two other siblings, older than thepropositus (one 10, one 11 years), had not been screenedin infancy and were also detected by family testing.

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678 Smith, Yu, and Brown

at 6 weeks in 44 of 55 babies. In 11 patients,arginine was not detected in the first test, althoughthe cystine and lysine levels were very high. Seven ofthese 11 patients showed the typical aminoaciduriain the second test; by this time the baby was usually3 months. There were 4 boys in whom increasedarginine excretion was not apparent at either of thefirst 2 blotting paper tests although cystine andlysine levels were very high; this was the indicationfor requesting a third test. Cystine, lysine, andarginine were all much increased in the subsequentliquid urine specimen in these children and haveremained so.

Patients were definitively diagnosed at about 6months, the 9 older siblings were diagnosed whenfamily studies were undertaken. All were reviewedduring the latter part of 1977 and first half of 1978.The age at last review ranged from 6 months to 22years (oldest sibling) with mean age 7-6 years. 49were at least 3 years and 28 were at least 8 years.Renal symptoms were present in 5 patients*. One boyhad an episode of renal calculus formation at age17j. One girl had episodes of right loin pain at 10i,and there were 2 cases of urinary tract infection, anda boy of 4 years had dysuria and a urinarytract infection; 4 months later a stone was detectedon routine x-ray. There were also 3 children (2boys, 1 girl) who were bed-wetters until about 9-10years and there were 3 asymptomatic girls whoshowed urinary contamination, but not infection ofurine, on routine microurine investigations atfollow-up.

Routine x-rays of the abdomen had been per-formed in 42 of the children (in some of the olderones more than once) and in one case a calculus wasseen which was asymptomatic. Routine tests formicroscopic haematuria were negative in everypatient at each follow-up.The general health ofthe children was good and not

significantly different from their siblings. There were9 cases with noteworthy childhood conditions. Oneboy had a hemivertebra ofL4 spine producing lumbarscoliosis; the adopted girl suffers from severe asthmarequiring daily medication; one girl at 3i years hasgrey carious irregular teeth; one boy aged 4 yearshad surgical correction of pyloric stenosis at 5months; and one boy, free of renal symptoms, had asalivary gland calculus removed surgically at 7 years.Another boy aged 9 also had surgery for pyloricstenosis as a baby. One girl had mild minor retarda-tion and attended the spastic centre until she was 5,and one boy had surgery for bilateral convergentstrabismus. One further patient has petit malepliepsy.*Details of individual cases are available from authors onrequest.

The growth of these homozygous cystinuricchildren appeared to be within the normal range. Themean birthweight was 3 * 07 kg (boys and girlscombined) with a range of 1-76 kg (in a 7-weekpreterm girl) to 4 - 28 kg. In 5 babies the birthweightwas low due to prematurity (including the twins),there were 2 term babies in whom the birthweight waslow, but in all the others it was average. Birth lengthwas not as consistently recorded as birthweight andwas not known for 20 of the children, but in theremainder the mean birth length was 52 5 cm. Twochildren had birth lengths <3rd centile, the restwere between 10th and 90th centiles.

Height of the children at last follow up (of the49 patients over 3 years) showed that 28 were on thesame centile as their midparent height centile, 18were above, and 4 were below this. Three of thesechildren had unaffected siblings who were alsobelow the midparent height centile, and the fourth,a 4-year-old boy, was on the 10th centile for height,the midparent height being on the 50th centile, buthe was an only child and so had no siblings forgrowth comparisons. The heights of theparentsof theadopted girl were not known, but she was on the 50thcentile for height.

Results of genetic studies are shown in Table 2using the genetic types as described by Rosenberget al. (1966). In one case there were no family dataas the patient had been adopted. In one family, theresults of family testing could not be reconciled withcurrent concepts of the genetic inheritance ofcystinuria. Of the remaining 43 families, 27 weretype I and 16 were of mixed genetic type, 6 in whichboth parents were carriers and 10 with one normalparent and one heterozygous parent.The sex ratio among the siblings of the patients

can be seen in Table 1 and is 0 * 5 for the homozygoussiblings, 0 * 61 for the heterozygous siblings, and 0 * 64for the normal siblings. Although there appear to beslightly more boys, particularly among the normalsiblings, this was not significant (P>0 1). Datafor sex ratio of newborn babies in N.S.W. wereobtained from the Commonwealth Bureau ofStatistics (Commonwealth Bureau of Statistics, 1978,personal communication).

There was no case of parental consanguinity inthese families, nor was there any consanguinity

Table 2 Genetic types in 45 familiesNo.

Type I 27 60Type 11-Ill 6 3I-II/111 10Unknown* 1 2.25Atypicalt 1 2.25

*An adopted child, tCase 15.



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known among either the maternal or paternal grand-parents. One child was adopted, and this informationwas not known in this case. Among the siblings ofthe propositi, there were 13 early 1st trimesterspontaneous abortions (in 9 of these families), 89pregnancies proceeded to term. Given that 15% ofall pregnancies abort, these findings indicate thatthere is no increased abortion rate among cystinuricheterozygotes. There were also 3 stillbirths and onecase of premature labour of twins, neither of whomsurvived. Altogether, fetal loss in these families wasnot excessive.

Information about relatives with kidney stones wassought but it became clear during history taking thatthese data were inconsistent from family to family.Many relatives were reported to have had 'kidneytrouble', but it was not always possible to verify theinformation. Only confirmed episodes of calculiamong the parents and maternal or paternal grand-parents are given, and hence this is a low estimateof the occurrence of renal calculi among relatives ofthe propositi. These data are shown in Table 3.These 14 relatives were tested and amino-acids werenormal in 12 of them, where the calculi were clearlynoncystine in composition. One paternal grand-father was a type t heterozygote cystinuric, and onematernal grandmother was a type m heterozygote.Stone analysis was not performed in either of these,but it would seem unlikely that the maternal grand-mother had had cystine stones but possible that thepaternal grandfather's stones contained cystine. Inaddition 2 of the fathers had each had a nephrectomyfor congenital anomalies of the kidney.

Intellectual achievement of the patients wassatisfactory. School progress is reported where atleast 2 full years of schooling have been completed atlast follow-up. This applied to 35 of the children, andof these, 14 were in the highest class for their age, 16were in the middle for their age and consideredaverage, and 5 were in the lowest class for their age.In this group of 5 slower children, one boy who wasrepeating his 3rd year of school was an only child,

Table 3 Relatives with renal calculiRelative No.

Mother 1FatherPaternal

grandmother 1grandfather 3*

Maternalgrandmother 4grandfather 5*

14

*Two required nephrectomies; one was a heterozygote type II cyst-inuric, the propositus coming from a mixed family 1-11/111.

2 boys had unaffected siblings considered to beaverage, one girl had 2 unaffected siblings also in thelowest class for their age, and one girl had an un-affected younger brother who had not yet startedschool. Of the 14 children in the highest class fortheir age, 3 were at the top and had excellent reports.One of these is the adopted girl, one girl was aheadof her two heterozygote siblings, and one boy, whohad attended a special opportunity class for intelli-gent children in his area, was advanced comparedwith his homozygote brother and his 2 otherunaffected siblings, who were all in the average class.Only 2 patients have completed their schooling,each was an elder sibling of a propositus. Both wereaverage pupils at school, one is now an officeworker and the other a student nurse.The remaining 26 children include the babies,

toddlers, preschool children and those who had notcompleted 2 full years of schooling. Developmentalprogress as assessed by milestones was entirelynormal in 25 of these children. One child (Case 31) ismentally retarded in the mild to moderate range.

Discussion

Cystinuria is a disorder of the transport of cystineand the dibasic amino-acids in both the renal tubuleand the intestine. The presence of markedly highlevels of cystine, lysine, and arginine in the urine ofour patients, often with cystine crystalluria, clearlyclassified them as homozygotes. No intestinalabsorption studies were undertaken. It is not alwayspossible in the initial tests to distinguish homo-zygotes from heterozygotes. In 4 of our patients theclassical aminoaciduria was not found in the firsttwo screening tests and appeared in the third andsubsequent test. A definitive diagnosis in thesechildren was delayed until their third test had beenperformed. Similar problems were encountered byLevy et al. (1972) who also found repeat testingnecessary in some cases; their urine screeningprogramme was the most comparable to our own.The programme in Wales (Bradley, 1975) was similarin structure, but cystine was detected by the nitro-prusside spot test initially. We found the nitro-prusside test to be very accurate for detecting cystinein the urine, but false-positives and false-negativesmay occur (Smith, 1977).The incidence of cystinuria, based on routine

screening of urine from normal infants, has recentlybeen reported by Thalhammer (1975) as part of acollaborative study from 6 centres; Levy reported anincidence of one in 15 841 in Massachusetts, Thal-hammer one in 1100 in Vienna, Hyanek in Praguefound one in 22065, Scriver in Montreal foundone in 14084, while in N.S.W. we reported an



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680 Smith, Yu, and Brown

incidence of one in 5069. On reviewing our data, itwas apparent that some cases of type II heterozygoteswere included. With these cases eliminated and usingan extended population sample, the incidence inN.S.W. has been reduced to one in 17 286. Thisfigure is very similar to the incidence reported byLevy, but is still quite different from those found byThalhammer (one in 1100), Hyanek (one in 22 065),and Bradley (1975) (one in 27 059 cases). Thesevarious figures may reflect true differences in theincidence of homozygous cystinuria throughoutthe world, or they may be the result of othermethods used to detect cases or different criteria forthe diagnosis of homozygous cystinuria.

Colliss et al. (1963) reported on the stature of44 patients with cystinuria, 42 ofwhom had had renalcalculus disease. The mean height, adjusted to theadult male population, was found to be 2 - 5 cm lessthan that of controls. Our data indicate that homo-zygous cystinuric children are not smaller thannormal children. The height of the cystinuric childrenwas below that expected using the midparent heightcentiles (Tanner et al., 1970) in only 4 children, but3 of these were nevertheless on the same heightcentiles as their unaffected siblings. In one case thepropositus was an only child. The parents' heightswere generally measured when the patients were seen,in some cases the father's height was reported by themother.The birth length data presented here, although

incomplete, suggest that affected children do notbegin life shorter than normal children. It may bethat the shorter stature noted by Colliss is the resultof renal calculus disease, as most of her patients hadrenal calculi; however, our 2 patients with calculi,a 17-year-old and a 4-year-old boy, were both on the75th centile for height.

Scriver et al. (1970) suggested that defectivebrain transport mechanisms in cystinuric patientsmay lead to mental retardation. No patient in ourgroup could be considered to be mentally retardeddue to cystinuria. One boy was retarded but, as hehad other handicaps and congenital deafness, itwould not seem justifiable to consider that theretardation was due to cystinuria. Excluding thispatient, the intellectual achievement of 35 childrenwho had completed at least 2 years of schoolingshowed a wide scatter with only 5 being in the lowestclass for their ages; they were, however, certainlynot retarded. Of the remaining children, the mile-stones were all adequate and comparable withunaffected siblings, although 10 children born in1977 were still too young to assess this accurately.Formal psychometry was not performed. Gold et al.(1977) did use psychometry on 26 patients in Canadaand the intelligence levels of their patients were no

different from those of their unaffected siblings orthe normal population.

If mental retardation affects 1 * 5% of the popula-tion and the incidence of homozygous cystinuria isone in 15 000, then the chance of both conditionsoccurring coincidentally would be one in 1 000 000,or 5 people in N.S.W. As noted, only one suchchild was found.The general health of these children was good and

was in no way impaired by also having homozygouscystinuria. A possible exception is the finding of 2cases of pyloric stenosis, but further studies will berequired to prove if an association exists between thetwo conditions. Considering the number of patientsand the length of time of follow up, there were veryfew renal symptoms. There were only 2 provedepisodes of calculus formation, one episode of renalpain for which no cause was found, and 2 cases ofurinary tract infection. This study suggests that renalsymptoms in children with cystinuria are rare.The management of all these children consisted ofincreased fluid intake to the limit of tolerance. Itwould be satisfying to think that follow-up of thepatients and encouragement to maintain increasedfluids was the reason for lack of renal symptoms but,in fact, it was difficult to know in most cases what thechild's fluid intake actually was, and fluid intakeappeared to fluctuate from time to time. Without acontrol group and stringent control of fluid intake,this aspect of management cannot be adequatelyassessed.Among this group ofhomozygote cystinurics, 60 %

of the informative cases were of type I inheritance,and 35% were mixed or compound types (Table 2).Bostrom and Hambraeus (1964), in their extensivesurvey of cystinuria in Sweden, showed that of 59families studied, 10 contained demonstrable hetero-zygotes (which they called semicystinuria),giving 83 % type I families. Out of 21 families studiedby Harris and Warren (1953), 6 contained demon-strable heterozygotes, leaving 71 % type I cystinurics(which they named completely recessive); Rosenberget al. (1966) studied 15 patients and found 60% to betype I. The frequency of the different genetic types ofcystinuria appears to vary with different populations,although in every large study, the completely recessiveor type I form is the most common. This applies toall those studies where the propositi have been mainlystone-forming patients, and also to our study wherethe patients were detected in an unselected way byurinary screening. It appears, therefore, that thegenetic type of the patient is not an important factorfor cystine stone formation in a patient withhomozygous cystinuria.We found 14 relatives who had had renal calculi

among 270 parents and grandparents (Table 3);



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accurate figures for the incidence of renal calculi inthis population are not available, but using theannual incidence of Malek (1977) ofone in 1000 of thepopulation in the USA, it does appear that ourfindings show an increase of noncystine stone forma-tion among the relatives of cystinurics.

We thank Elizabeth McKenzie for help in compilingthe data and Beryl Morris for typing the manuscript.The late Brian Turner first took an interest in urinaryscreening for cystinuria and encouraged us tocontinue follow-up of patients detected.

References

Bostrom, H., and Hambraeus, L. (1964). Cystinuria inSweden. VII. Clinical, histo-pathological, and medico-social aspects of the disease. Acta medica Scandinavica,175, Supplement 411.

Bradley, D. M. (1975). Screening for inherited metabolicdisease in Wales using urine-impregnated filter paper.Archives of Disease in Childhood, 50, 264-268.

Colliss, J. E., Levi, A. J., and Milne, M. D. (1963). Statureand nutrition in cystinuria and Hartnup disease. BritishMedical Journal, 1, 590-592.

Gold, R. J. M., Dobrinski, M. J., and Gold, D. P. (1977).Cystinuria and mental deficiency. Clinical Genetics, 12,329-332.

Harris, H., and Warren, F. L. (1953). Quantitative studies onthe urinary cystine in patients with cystine stone formationand in their relatives. Annals of Eugenics, 18, 125-171.

Hepler, 0. I. (1950). Manual of Clinical Laboratory Methods,fourth edition, p. 21. Thomas: Springfield.

Levy, H. L., Madigan, P. M., and Shih, V. E. (1972). Massa-chussetts metabolic disorders screening program. I.Technics and results of urine screening. Pediatrics, 49,825-836.

Malek, K. S. (1977). Renal lithiasis: a practical approach.Review article. Journal of Urology, 118, 893-901.

Rootwelt, K. (1967). Quantitative determination of thiolsand disulphides in urine by means of Ellman's reagent andthiolated sephadex, and its application in cystinuria.Scandinavian Journal of Clinical and Laboratory Investiga-tion, 19, 325-330.

Rosenberg, L. E., Downing, S., Durant, J. L., and Segal, S.(1966). Cystinuria: biochemical evidence for three genetic-ally distinct diseases. Journal of Clinical Investigation, 45,365-371.

Scriver, C. R., Whelan, D. T., Clow, C. L., and Dallaire, L.(1970). Cystinuria: increased prevalence in patients withmental disease. New England Journal of Medicine, 283,783-786.

Smith, A. (1977). Evaluation of the nitro-prusside test in thediagnosis of cystinuria. Medical Journal of Australia, 2,153-155.

Smith, 1. (1969). Chromatographic and ElectrophoreticTechniques, third edition, p. 121. Heinemann: London.

Tanner, J. M., Goldstein, H., and Whitehouse, R. H. (1970).Standards for children's height at ages 2-9 years allowingfor height of parents. Archives of Disease in Childhood, 45,755-762.

Thalhammer, 0. (1975). Frequency of inborn errors ofmetabolism, especially PKU, in some representative new-born screening centres around the world. A collaborativestudy. Humangenetik, 30, 273-286.

Wilcken, B., Smith, A., Gaha, T. J., McLeay, A. C., andBrown, D. A. (1973). Screening for metabolic diseases in'New South Wales. Medical Journal of Australia, 1, 1129-1133.

Correspondence to Dr A. Smith, Health Commissionof New South Wales, Oliver Latham Laboratory,PO Box 53, North Ryde, New South Wales 2113,Australia.

Received 24 October 1978



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