Prenatal diagnosis of rhizomelic chondrodysplasia punctata due to isolated alkyldihydroacetonephosphate acyltransferase synthase deficiency

  Prenat. Diagn. 19: 383–385 (1999)

SHORT COMMUNICATION

Prenatal Diagnosis of Rhizomelic Chondrodysplasia Punctata Due to Isolated Alkyldihydroacetonephosphate Acyltransferase Synthase Deficiency Karen M. Brookhyser1*, Mark H. Lipson1, Ann B. Moser2, Hugo W. Moser2, Ralph S. Lachman3 and David L. Rimoin3 1

Department of Medical Genetics, Kaiser Permanente, Sacramento, CA, U.S.A. Kennedy Krieger Institute, Peroxisomal Diseases Laboratory, Baltimore, MD, U.S.A. 3 Medical Genetics–Birth Defects Center, Cedars—Sinai Medical Center, Los Angeles, CA, U.S.A. 2

Current practices in prenatal diagnosis of rhizomelic chondrodysplasia punctata (RCDP) are reviewed. A case is presented with a family having one daughter affected with RCDP due to alkyldihydroacetonephosphate acyltransferase synthase (DHAPAT synthase) deficiency, and three subsequent pregnancies. Biochemical test values are presented for the pregnancies and daughter. Post-mortem tests of one fetus of a terminated pregnancy showed that radiologic examination could not make the diagnosis of RCDP. We conclude that biochemical or molecular testing is necessary to accurately diagnose this type of RCDP prenatally. Copyright  1999 John Wiley & Sons, Ltd.  : prenatal diagnosis; rhizomelic chondrodysplasia punctata; DHAPAT synthase deficiency; dwarfism

INTRODUCTION Rhizomelic chondrodysplasia punctata (RCDP) is an autosomal recessive disorder characterized by severe limb shortening, punctate calcification of cartilage, flexion contractures, vertebral clefts, cataracts, characteristic facial appearance, severe growth deficiency and mental retardation (Heymans and Wanders, 1996; Spranger et al., 1971). While many patients do not survive beyond the first years, some have survived to five years of age or older (Wardinsky et al., 1990) and a few patients with the classical phenotype are alive in their second and third decade. Three genotypes have been identified. Type 1 is associated with a defect in the PEX7 gene, which codes for the receptor of peroxisome targeting sequence 2 (Braverman et al., 1997; Motley et al., 1997; Purdue et al., 1997). The main biochemical abnormalities are a profound deficiency of plasmalogens due to impaired activity of dihydroxyacetonephosphate (DHAP) acyltransferase (Heymans et al., 1985) and alkyl-DHAP synthase (Heymans and Wanders, 1996); increased levels of plasma phytanic acid due to deficiency of phytanoyl-CoA hydroxylase, an enzyme which contains the peroxisome targeting sequence 2 (Jansen et al., 1997); and impaired processing of peroxisomal 3-ketothiolase (Heymans and Wanders, 1996). In Type 2 there is an isolated deficiency of DHAP acyltransferase (DHAPAT) (Barr et al., 1992; Clayton et al., *Correspondence to: K. Brookhyser, Department of Medical Genetics, Kaiser Permanente, 1650 Response Road, Sacramento, CA 95815, U.S.A.

CCC 0197–3851/99/040383–03$17.50 Copyright  1999 John Wiley & Sons, Ltd.

1994; Hebestreit et al., 1996; Sztriha et al., 1997; Wanders et al., 1992) and in Type 3 a defect of alkyl-DHAP synthase (de Vet et al., 1998; Wanders et al., 1994). Plasmalogen levels are reduced in type 2 and 3 patients while phytanic acid levels and the processing of 3-ketothiolase are normal. The observation that type 2 and 3 patients may display the classical phenotype suggests that the pathogenesis of RCDP may be due solely to a deficiency of plasmalogens (Heymans and Wanders, 1996). While all three genotypes are associated most commonly with the classical phenotype, milder phenotypes have been described. These include patients in whom the limbs were normal in length and early psychomotor development was normal (Nuoffer et al., 1994; Poll-The et al., 1991; Smeitink et al., 1992). These patients were shown to have the type 1 genotype (Motley et al., 1996). The non-rhizomelic phenotype has also been reported in the type 2 genotype (Sztriha et al., 1997). One patient who probably had the type 1 genotype showed only minimal punctate stippling (Gray et al., 1992). Prenatal diagnosis of RCDP is available in the first and second trimester by biochemical analysis of fetal cells from chorionic villus sampling (Hoefler et al., 1988) and amniocentesis (Gray et al., 1990). RCDP has also been reported to be diagnosed prenatally by ultrasound and X-ray studies. Rhizomelic limb shortening in RCDP has been reported in the second (Sastrowijoto et al., 1994) and third (Duff et al., 1990; Gendall et al., 1994) trimesters. Abnormal appearance of fetal epiphyseal cartilage has been noted with RCDP in the second (Sastrowijoto et al., 1994; Sherer et al., Received 30 June 1998 Revised 2 November 1998 Accepted 2 November 1998

. .   .

384

Table 1—Fibroblast peroxisomal plasmalogen synthesis enzymes

Control Affected daughter 3/95 pregnancy (affected) 10/95 pregnancy (affected) 5/97 fetus (unaffected)

Cultured amniotic fluid cells Skin fibroblasts Cultured amniotic fluid cells Skin fibroblasts Cultured amniotic fluid cells

3H/14C ratio

14C/3H ratio

0.670.19 36.39 31.88 38.24 36.70 52.86 0.75

1.650.66 0.05 0.03 0.03 0.03 0.02 1.34

The incorporation of radioactivity was measured in alkenyl phosphatidyl ethanolamine (alkenyl PE) in cultured amniotic fluid cells. 14C radioactivity incorporation measures peroxisomal steps in plasmalogen synthesis. 3H counts are a measurement of peroxisomal and microsomal steps in plasmalogen synthesis. Method reference: Roscher et al. (1985).

1994) and third trimesters (Duff et al., 1990; Hyndman et al., 1976). We report here a case of type 3 RCDP in which biochemical studies confirmed the diagnosis but where prenatal second-trimester ultrasound and post-mortem radiographic studies were normal. CASE REPORT A 34-year-old G4 P3 Lebanese woman presented to us in January, 1995 at eight weeks post LMP. She and her husband were first cousins who had two normal daughters and a four-year-old daughter with severe retardation who was known to be affected with a variant form of RCDP. The affected daughter was identified at four months of age with cataracts, rhizomelic shortening of the limbs and stippled epiphyses. She had a deficiency in DHAPAT synthase activity (19.2 per cent of control) but normal DHAPAT (57.3 per cent of control) and normal phytanic acid oxidase activity in blood and skin fibroblasts (Moser et al., 1995). Complementation studies (Moser et al., 1995) indicated the patient had isolated DHAPAT synthase deficiency (data not shown). Plasma very long chain fatty acids were normal. The plasmalogen levels in red blood cells were measured by determining the ratios of C16:0 and C18:0 dimethylacetals to C16:0 and C18:0 fatty acids (Bjorkhem et al., 1986). As expected, these ratios were reduced, to 0.016 for C16:0 (control 0.0650.010) and 0.015 for C18:0 (control 0.1950.015). Prenatal diagnosis was performed by amniocentesis at 13 weeks’ gestation. Chromosomes were normal male (46,XY) and amniotic fluid alpha-fetoprotein and acetylcholinesterase were normal. The ultrasound performed at the time of the amniocentesis did not reveal any fetal bone abnormalities. Biochemical analysis of cultured amniocytes revealed a marked deficiency of peroxisomal plasmalogen synthesis similar to that diagnosed in the affected living daughter (see Table 1). Therefore the fetus was determined to be affected with RCDP. The couple terminated the pregnancy by D&E at 17 weeks post LMP. Biochemical studies from fetal tissue confirmed the diagnosis of type 3 RCDP (see Copyright  1999 John Wiley & Sons, Ltd.

Table 1). Post-mortem histology from cartilage was consistent with the known pathology of RCDP, which includes reduction in the preparatory zone of calcification and the columnar cartilage combined with a disorganization of the normal cartilage arrangement (Sugarman, 1974). X-ray studies failed to find significant rhizomelia, vertebral changes or punctate calcifications. All long bone measurements were at the 50th percentile for gestational age of 15 to 16 weeks. We saw this family for prenatal diagnosis in two more pregnancies. Fibroblast peroxisomal plasmalogen synthesis data from the affected daughter and the mother’s subequent three pregnancies are shown in Table 1.

DISCUSSION Although RCDP may present with ultrasound findings in the fetus, caution should be used when attempting to rule out the diagnosis of RCDP, since, as noted in the introduction, non-rhizomelic forms have been reported with type 1 and type 2 genotypes. Gray et al. (1990) noted that limb shortening was not present in an abortus of 20 weeks duration who probably had the type 1 phenotype since only the immature form of peroxisomal 3-ketothiolase was present. Our report makes it clear that ultrasound and X-ray studies can also be normal in type 3 RCDP. The normal results in this instance were likely due to the early gestational age of the fetus since the affected sibling did have abnormal skeletal findings postnatally. Accurate diagnosis of alkyl-DHAP synthase deficient RCDP requires biochemical or molecular testing. Since type 1 and type 2 RCDP patients may also be associated with normal prenatal and only mildly abnormal postnatal radiological changes, it seems prudent to apply the lesson learned from this patient with alkyl-DHAP synthase deficiency to all RCDP cases. Diagnostic testing may involve direct DNA or more traditional biochemical testing, but these are the appropriate and necessary types of studies to make a conclusive diagnosis of RCDP. Prenat. Diagn. 19: 383–385 (1999)

      We wish to thank Dr Amya K. Hajra for performing the assays for DHAPAT synthase and DHAPAT.

REFERENCES Barr DGD, Kirk JM, Howasi MA, Wanders RJA, Schutgens RBH. 1992. Rhizomelic chondrodysplasia punctata with isolated DHAP-AT deficiency. Arch Dis Chld 68: 415–417. Bjorkhem I, Sisfontes L, Bostrom B, Kase BF, Blomstrand R. 1986. Simple diagnosis of the Zellweger syndrome by gas–liquid chromatography of dimethylacetals. J Lipid Res 27: 786–791. Braverman N, Steel G, Obie C, Moser A, Moser H, Gould S, Valle D. 1997. Human PEX7 encodes the peroxisomal PTS2 receptor and is responsible for rhizomelic chondrodysplasia punctata. Nature Genet 15: 369–376. Clayton PT, Eckhardt S, Wilson J, Hall CM, Yousuf Y, Wanders RJA, Schutgens RBH. 1994. Isolated dihydroxyacetonephosphate acyltransferase deficiency presenting with developmental delay. J Inher Metab Dis 17: 533–540. de Vet ECJM, Lodewijk IJ, Oostheim W, Wanders RJ, van den Bosch H. 1998. Alkyl-dihydroxyacetonephosphate synthase: fate in peroxisome biogenesis disorders and identification of the point mutation underlying a single enzyme deficiency. J Biol Chem 273: 10 296–10 301. Duff P, Harlass F, Milligan D. 1990. Prenatal diagnosis of chondrodysplasia punctata by sonography. Ob Gyn 76: part 2.497–500. Gendall PW, Baird CE, Becroft DM. 1994. Rhizomelic chondrodysplasia punctata: early recognition with antenatal ultrasonography. J Clin Ultrasound 22: 271–274. Gray RG, Green A, Schutgens RB, Wanders RJ, Farndon PA, Kennedy CR. 1990. Antenatal diagnosis of rhizomelic chondrodysplasia punctata in the second trimester. J Inher Metab Dis 13: 380–382. Gray RG, Green A, Chapman S, McKeown C, Schutgens RB, Wanders RJ. 1992. Rhizomelic chondrodysplasia punctata—a new clinical variant. J Inher Metab Dis 15: 931–932. Hebestreit H, Wanders RJA, Schutgens RBH, Espeel M, Kerckaert L, Roels F, Schmausser B, Schrod L, Marx A. 1996. Isolated dihydroxyacetonephosphate-acyltransferase deficiency in rhizomelic chondrodysplasia punctata: clinical presentation, metabolic and histological findings. Eur J Pediatr 155: 1035–1039. Heymans HS, Oorthuys JW, Nelck G, Wanders RJ, Schutgens RB. 1985. Rhizomelic chondrodysplasia punctata: another peroxisomal disorder. N Engl J Med 313: 187–188. Heymans HS, Wanders RJA. 1996. Rhizomelic chondrodysplasia punctata. In: Moser HW (ed) Handbook of Clinical Neurology: Neurodystrophies and Neurolipidoses. Amsterdam: Elsevier Science BV. Hoefler S, Hoefler G, Moser AB, Watkins PA, Chen WW, Moser HW 1988. Prenatal diagnosis of rhizomelic chondrodysplasia punctata. Prenat Diagn 8: 571–576. Hyndman WB, Alexander DS, Mackie KW. 1976. Chondrodystrophia calcificans congenita (the Conradi–Hunermann syndrome). Clin Pediatr 15: 317–321. Jansen GA, Mihalik SJ, Watkins PA, Moser HW, Jakobs C, Heumans HSA, Wanders RJA. 1997. Phytanoyl-CoA hydroxylase is not only deficient in classical refsum disease but also in rhizomelic chondrodysplasia punctata. J Inher Metab Dis 20: 444–446.

Copyright  1999 John Wiley & Sons, Ltd.

385

Moser AB, Rasmussen M, Naldu S, Watkins PA, McGuinness M, Hajra AK, Chen G, Raymond G, Liu A, Gordon D, Garnaas K, Walton DS, Skjeldal OH, Guggenheim MA, Jackson LG, Elias ER, Moser HW. 1995. Phenotype of patients with peroxisomal disorders subdivided into sixteen complementation groups. J Pediatr 127: 13–22. Motley AM, Tabak HF, Smeitink JAM, Poll-The BT, Barth PG, Wanders RJ. 1996. Non-rhizomelic chondrodysplasia and rhizomelic chondrodysplasia punctata within a single complementation group. Biochim Biophys Acta 1315: 153–158. Motley AM, Hettema EH, Hogenhout EM, Brites P, Asbroek A, Wijburg FA, Baas F, Heijmans HS, Tabak HF, Wanders RI, Distel B. 1997. Rhizomelic chondrodysplasia punctata is a peroxisomal protein targeting disease caused by a non-functional PTS2 receptor. Nature Genet 15: 377–380. Nuoffer JM, Pfammatter JP, Spahr A, Toplak H, Wanders RJ, Schutgens RB, Wiesmann UN. 1994. Chondrodysplasia punctata with a mild clinical course. J Inher Metab Dis 17: 60–66. Poll-The BT, Maroteaux P, Narcy C, Quetin P, Guesnu M, Wanders RJA, Schutgens RBH, Saudubray JM. 1991. A new type of chondrodysplasia punctata associated with peroxisomal dysfunction. J Inher Metab Dis 14: 361–363. Purdue PE, Zhang JW, Skoneczny M, Lazarow PB. 1997. Rhizomelic chondrodysplasia punctata is caused by deficiency of human PEX7, a homologue of the yeast PTS2 receptor. Nature Genetics 15: 381–384. Roscher A, Molzer B, Bernheimer H, Stockler S, Mutz I, Paltauf F. 1985. The cerebrohepatorenal (Zellweger) syndrome: an improved method for the biochemical diagnosis and its potential value for prenatal detection. Pediatr Res 19: 930–933. Sastrowijoto SH, Vandenberghe K, Moerman P, Lauweryns JM, Fryns JP. 1994. Prenatal ultrasound diagnosis of rhizomelic chondrodysplasia punctata in a primigravida. Prenat Diagn 14: 770–776. Sherer DM, Glantz JC, Allen TA, Lonardo F, Metlay LA. 1994. Prenatal sonographic diagnosis of non-rhizomelic chondrodysplasia punctata. Ob Gyn 83: part 2: 858–860. Smeitink JAM, Beemer FA, Espeel M, Donckerwolcke RA, Jakobs C, Wanders RJA, Schutgens RBH, Roels F, Duran M, Dorland L, Berger R, Poll-The BT. 1992. Bone dysplasia associated with phytanic acid accumulation and deficient plasmalogen synthesis: a peroxisomal entity amenable to plasmapheresis. J Inher Metab Dis 15: 377–380. Spranger JW, Opitz JM, Bidder U. 1971. Heterogeneity of chondrodysplasia punctata. Humangenetick 11: 190–212. Sugarman GI. 1974. Chondrodysplasia punctata (rhizomelic type): case report and pathologic findings. Birth Defects 10: 334–340. Sztriha LS, Nork MP, Abdulrazzaq YM, Al-Galazi LI, Bakalinova DB. 1997. Abnormal myelination in peroxisomal isolated dihydroxyacetonephosphate acyltransferase deficiency. Pediatr Neurol 16: 232–236. Wanders RJ, Schumacher H, Heikoop J, Schutgens RB, Tager JM. 1992. Human dihydroxyacetonephosphate acyltransferase deficiency: a new peroxisomal disorder. J Inher Metab Dis 15: 389–391. Wanders RJ, Dekker C, Hovarth VA, Schutgens RB, Tager JM, van Laer P, Lecoutere D. 1994. Human alkyldihydroxyacetonephosphate synthase deficiency: a new peroxisomal disorder. J Inher Metab Dis 17: 315–318. Wardinsky TD, Pagon RA, Powell BR, McGillivray B, Stephan M, Zonana J, Moser A. 1990. Rhizomelic chondrodysplasia punctata and survival beyond one year: a review of the literature and five case reports. Clin Genet 38: 84–93.

Prenat. Diagn. 19: 383–385 (1999)