Lethal Osteosclerotic Osteochondrodysplasia WithPlatyspondyly, Metaphyseal Widening, andIntracellular Inclusions in Sibs

Steven G. Brodie,1 Ralph S. Lachman,1,3 Ann F. Jewell,4 Carey L. Winkler,4 Loyda Nolasco,1 andWilliam R. Wilcox1,2*1Ahmanson Department of Pediatrics, Steven Spielberg Pediatrics Research Center, Cedars-Sinai Burns and AllenResearch Institute, Los Angeles, California

2Department of Pediatrics, UCLA School of Medicine, Los Angeles, California3Department of Radiology, UCLA School of Medicine, Los Angeles, California4Carilion Center for Women and Children, Community Hospital of Roanoke Valley, Roanoke, Virginia

We report on a previously undescribed formof lethal osteosclerotic skeletal dysplasia insibs from nonconsanguineous parents. Ra-diographic findings included increased den-sity in the base of the skull, clavicles, verte-brae, ribs, and the metaphyseal regions ofthe long bones. There was midface hypopla-sia, a large anterior fontanel, micrognathia,and hypoplastic, wafer-thin vertebrae. Theclavicles, ribs, metacarpals, metatarsals,and phalanges were especially thickenedand widened. The long bones were short-ened with flared metaphyses. Chondro-osseous morphology of resting cartilage andgrowth plate was relatively normal, butthere was hypercellular cortical and trabec-ular bone, and marrow fibrosis. Ultrastruc-turally, the resting chondrocytes, osteo-blasts, and nonhematopoietic marrow cellshad dilated rough endoplasmic reticulum(inclusion bodies). The radiographic andmorphologic characteristics in this case areunique and differ from those seen in otherpreviously reported lethal osteoscleroticskeletal dysplasias. Am. J. Med. Genet. 80:423–428, 1998. © 1998 Wiley-Liss, Inc.

KEY WORDS: osteosclerosis; inclusion bod-ies; lethal skeletal dysplasia

INTRODUCTION

The lethal osteosclerotic skeletal dysplasias are aheterogeneous group of disorders with increased den-sity of trabecular bone, usually presenting in the peri-natal period [Spranger and Maroteaux, 1990; Taybiand Lachman, 1996]. Osteopetrosis, hyperostosis, andosteosclerosis entities all have sclerotic bones and arethought to arise by abnormal modeling and/or remod-eling of the bone. The underlying defects in most ofthese disorders have yet to be elucidated [Gelb et al.,1996; Johnson et al., 1997; Sly and Hu, 1995; Whyte,1997].

We report on the clinical, radiographic, and morpho-logic findings in a previously undescribed form of lethalosteosclerotic skeletal dysplasia.

CLINICAL REPORT

Case 1. [Registry # 95-106A] This 38-week gesta-tion girl was born to an 18-year-old gravida 3 para 2Caucasian mother and a 20-year-old father. Fetal ul-trasonography at 13-weeks showed long bones measur-ing less than the 5th centile in length for gestationalage. The chest appeared small with a circumference of113 mm (2nd centile). The hands were abnormallyshaped with prominent and wide-spaced digits. FGFR3analysis did not show the achondroplasia G380R mu-tation. The karyotype was 46,XX. Subsequent ultra-sound examinations continued to show a small chestand limbs. At birth, the infant weighed 800 g and theplacenta weighed 160 g. No breath sounds were notedand the infant died one hour after birth of severe pul-monary hypoplasia. At autopsy, there was macro-cephaly with frontal bossing, a depressed nasal bridge,narrow thorax, hypoplastic lungs, micromelia withmildly curved femora, camptodactyly, and mild con-tractures of the elbows and knees. The combinedweight of the heart and lungs was 16.8 g. There were noother gross or microscopic abnormalities of the viscera.There was no demarcation between the cortical greyand white matter of the brain.

Contract grant sponsor: National Institutes of Health; Contractgrant number: SP01-HD 22657.

*Correspondence to: William R. Wilcox, M.D., Ph.D., MedicalGenetics, Cedars-Sinai Medical Center, 8700 Beverly Blvd., SSB-3, Los Angeles, CA 90048. E-mail: wwilcox@cshs.org

Received 1 July 1998; Accepted 12 August 1998

American Journal of Medical Genetics 80:423–428 (1998)

© 1998 Wiley-Liss, Inc.

Case 2. [Registry # 95-106B] The couple’s subse-quent pregnancy was terminated at 18-weeks of gesta-tion for suspected recurrence based on similar ultra-sound images of shortened long bones (less than the5th centile) and a small chest (5th to 10th centile).

Family History

The parents were nonconsanguineous of Caucasiandescent. The mother had two healthy children by twoother unions. The maternal grandmother reportedlyhad three or four spontaneous abortions, and a mater-nal aunt is reported to have a son who will be no taller

than 122 cm, suggestive of a dwarfing syndrome. Oneof the paternal aunts had a stillborn son. Otherwise thefamily history is unremarkable. Subsequent to thecases reported here, the couple had an apparentlyhealthy son.

METHODS

Formalin fixed chondro-osseous tissue was processedundecalcified in glycol and methyl methacrylate. Sec-tions were stained with Von Kossa trichrome, toluidineblue, alcian blue, and Goldner’s stains. For electronmicroscopy and immunohistochemistry, cartilage from

Fig. 1. Postmortem anteroposterior (A), lateral (B), and pelvic (C) radiographs of Case 1 showing disproportionate shortness of the limbs. Note theincreased density of the cranial bones, spine, metaphyseal regions of the long bones and pelvis.

424 Brodie et al.

the resting zone was examined as described previously[Brodie et al., 1998].

RESULTS

Radiographic Findings

Case 1. Postmortem radiographs (Fig. 1) showedmidface hypoplasia, a large anterior fontanel, and asclerotic, small mandible. The vertebrae were dense,hypoplastic, and wafer-thin with dense posterior ele-ments. The clavicles were thickened, distally widened,and dense. The body of the scapulae had relatively nor-mal architecture, but was dense with severe glenoidhypoplasia and a prominent acromion. The ribs weremoderately shortened, uniformly thickened, somewhatirregular, and dense. The ilia had increased bone den-sity of the crest and the supra-acetabular region. Theiliac wings were flared and rounded, and the acetabu-lar roof was flattened. The sacrosciatic notches were

mildly narrowed. The ischium and pubic bones weresomewhat dense but otherwise normal. The long boneshad severe shortening, moderate diaphyseal widening,and metaphyseal flaring. The femora had roundedproximal metaphyses and flared distal metaphysesthat were mildly cupped. There was significant proxi-mal fibular overgrowth. In the hands the metacarpalsand phalanges were widened and there was also wid-ening of the short tubular bones of the feet. The ankleshowed ossification of the talus with stippling in theregion of the calcaneus.

Case 2. The radiographs were similar to those ofCase 1, although there was less bone density in allareas and there was stippling in the area of the calca-neus (Fig. 2).

Chondro-osseous Morphology

Histopathologic examination of the costochondraljunction, iliac crest, femur, tibia, and vertebrae fromCase 2 showed decreased calcified cartilage, decreasedcalcospherites, thin primary spongiosa, fibrotic mar-row cavities, and increased periosteal bone (Fig. 3). Thecortical bone was thin and hypercellular. The trabecu-lar bone was thick and hypercellular.

Ultrastructurally, the resting cartilage chondrocyteshad dilated rough endoplasmic reticulum (inclusionbodies) and a normal appearing matrix (Fig. 4A) inboth cases. Both cases also had inclusions in osteo-blasts (Fig. 4B), while inclusions in osteocytes werefound only in Case 1. The marrow was largely replacedby collagenous fibrosis, and the nonhematopoietic cellsin the marrow also had large inclusion bodies. No in-clusions were found in the endothelial cells of the mar-row vessels. Cultured fibroblasts were normal fromCase 2, and no skin was available for electron micro-scopic examination.

Immunohistochemistry

Immunohistochemical studies using antibodies spe-cific for collagens (Type II, IX, and X), aggrecan, versi-can, and cartilage oligomeric matrix protein were per-formed on frozen tissues. There were no detectable dif-ferences in matrix staining compared with controls,and there was no staining of the rER inclusions. Con-

Fig. 2. Postmortem anteroposterior radiograph of Case 2. Note the ra-diographic changes similar to Case 1.

Fig. 3. Chondro-osseous morphology of the tibia from Case 2. (A) Notethe thin, hypercellular cortical bone, coarse, widened trabecular bone, andthe fibrotic marrow spaces. Goldner’s stain ×4.

Lethal Osteosclerotic Osteochondrodysplasia 425

trol sections of achondrogenesis II/hypochondrogenesismaterial showed staining of inclusions only with TypeII collagen antibodies.

DISCUSSION

The clinical, radiographic, and morphologic findingsin these sibs comprise a previously undescribed lethal

osteosclerosis. The increased density in the base of theskull, maxilla, vertebrae, ribs, and diametaphyseal re-gions of the long bones distinguish the present casesfrom previously reported cases of lethal osteoscleroticskeletal dysplasias (Table I).

Our cases share some similarities with other re-ported cases of lethal osteosclerotic skeletal dysplasias.

Fig. 4. Transmission electron micrograph of the femur resting cartilage and bone from Case 1. Note the loops of dilated rough endoplasmic reticulumchondrocytes (A, ×13,500) and osteoblasts (B, ×8750).

TABLE I. Summary of Findings in Lethal Osteosclerotic Skeletal Dysplasias

Case 1 Case 2Raine

syndrome

Lethalmetatropicdysplasia

Pyknoachon-drogenesisa

Greenbergdysplasia

Dappleddiaphysealdysplasia

Astley-Kendall

dysplasiaBlomstranddysplasia

Clinical findingsMidface hypoplasia + + + − − + + − +Flattened hypoplastic nose + + + − + − − − +Micrognathia + + + − − − − − +Small chest + + + + + + + + +Limb shortening + + − + + + + + +

Radiographic findingsOsteosclerosis

Skull + + − − + + + − −Vertebrae + + − + − + + + −Long bones + + − + + + + + +

Hypoplastic vertebrae + + − + − + + + +Short ribs + + − + + − − − +Flattened acetabular roofs + + − + − − − − −

MorphologyBony overgrowth + + − − ? − − − −Dilated rER + + − − ? + ? − −

aCamera et al., 1986.

426 Brodie et al.

The midface hypoplasia and irregular mandible arealso found in Raine syndrome, but the microcephaly,abnormal facial appearance, and poor corticomedullarydemarcations of the long bones are not found in ourcases [Al Mane et al., 1996; Kan and Kozlowski, 1992;Raine et al., 1989]. Manifestations of the lethal form ofmetatropic dysplasia also includes short ribs, shortlimbs with expanded ends, and dense platyspondylythat overlaps with our cases, but the vertebral anoma-lies and pelvic changes are not similar to our cases[Perri, 1978; Colavita and Kozlowski, 1984]. Greenbergdysplasia and dappled diaphyseal dysplasia also havemanifestations of increased density in the cranial baseand facial bones, limb shortening, and platyspondyly;but the hyoid and crycoid calcifications, hydrops fetalis,11 pairs of shortened ribs, elongated clavicles, extraossification centers in the spine, and postaxial polydac-tyly were not found in our cases [Chitayat et al., 1993].Blomstrand dysplasia has manifestations of midfacehypoplasia, an irregular mandible, limb shortening,short ribs, micrognathia, and metaphyseal flaring ofthe long bones, which were found in our cases, but alsohas precocious calcification of the hyoid and crycoidcartilage, a flattened hypoplastic nose, polyhydrami-nos, and hypertelorism [Blomstrand et al., 1985; Younget al., 1993]. Astley-Kendall form of osteosclerotic skel-etal dysplasia has manifestations of calcified costal car-tilage, ‘‘S’’ shaped ribs with decreased ossification, ribfractures, multiple ossification centers and translucentdefects in the pelvis, and small iliac wings [Nairn andChapman, 1989], none of which were found in ourcases.

The chondro-osseous morphology in this case is verysimilar to that of other forms of lethal skeletal dyspla-sias. Overall the cartilage and growth plate were nor-mal. The cortical bone was abnormal, being hypercel-lular and not parallel. There was mild overgrowth ofperichondral bone, which is nonspecific and frequentlyseen in other lethal skeletal dysplasias such as thana-tophoric dysplasia, short rib polydactyly I/III, and theplatyspondylic lethal skeletal dysplasias; but the chon-drocyte columns are short in those disorders [Horton etal., 1979; Wilcox et al., 1998a; Martınez-Frıas et al.,1993]. The marrow fibrosis was most severe in the me-taphyses as opposed to the generalized fibrosis found inosteogenesis imperfecta (OI) type II and Pacman dys-plasia [Bullough et al., 1981; Wilcox et al., 1998b].

rER inclusion bodies within chondrocytes are consis-tently found in a number of chondrodysplasias. Thepresence of rER inclusion bodies in our case suggests itmay also be due to a defect in an extracellular matrixprotein or another protein trafficked through the rER.Immunohistochemical studies excluded collagens (typeII, IX, and X), aggrecan, and cartilage oligomeric ma-trix protein.

Inclusion bodies were also found in osteoblasts fromboth cases and in the osteocytes in the first case. Os-teoblast inclusions are found in OI but chondrocyte in-clusions are not found in that disorder [Bullough et al.,1981; Jones et al., 1984]. No inclusions were found inthe endothelial cells of the marrow vessels, but thenonhematopoietic cells in the marrow also had largeinclusion bodies. The presence of inclusion bodies in

bone and cartilage is unique and suggests abnormalityin a protein common to the mesenchymal lineage.

Although we cannot exclude the possibility of go-nadal mosaicism for a sporadic dominant disorder, wepropose that this new form of lethal osteosclerotic dis-ease is most likely inherited in an autosomal recessivefashion.

ACKNOWLEDGMENTS

The authors thank Dr. David L. Rimoin for reviewingthe manuscript, Maryann Priore and Roberta Bonac-quisti for administering the International SkeletalDysplasia Registry, and Betty Mekikian and ChristineKim for technical assistance.

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