schmid type of metaphyseal chondrodysplasia and col10a1 mutations—findings in 10 patients

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  • American Journal of Medical Genetics 137A:241248 (2005)

    Schmid Type of Metaphyseal Chondrodysplasia andCOL10A1 MutationsFindings in 10 PatientsOuti Makitie,1,2* Miki Susic,1 Leanne Ward,3,4 Catherine Barclay,1 Francis H. Glorieux,4 and William G. Cole1

    1Division of Genetics and Genomic Biology, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada2Hospital for Children and Adolescents, Helsinki University Hospital, Helsinki, Finland3Department of Pediatrics, University of Ottawa, Ottawa, Ontario, Canada4Genetics Unit, Shriners Hospital for Children, McGill University, Montreal, Quebec, Canada

    The Schmid type of metaphyseal chondrody-plasia (MCDS) is characterized by short stature,widened growth plates, and bowing of the longbones. It results from autosomal dominant muta-tions of COL10A1, the gene which encodes a1(X)chains of type X collagen. We report the clinicaland radiographic findings in 10 patients withMCDS and COL10A1 mutations. Six patients hadlower limb deformities, which necessitated ortho-pedic surgeries in all of them. One patient demon-strated no deformities and normal stature atage 11 years (height 1.2 SDS) while the othersmanifested severe short stature (

  • were ascertained thorough clinical genetic, orthopaedic, andpediatric services. The diagnosis ofMCDSwas based clinicallyon short-limbed short stature and absence of evident extra-skeletal manifestations and radiographically, on compatiblemetaphyseal changes on skeletal radiographs [Lachman et al.,1988; Warman et al., 1993]. Causative mutations in COL10A1were identified in 11 patients. One of these patients haspreviously been described [Baric et al., 2000]; the remaining10 patients were included in the present report.

    Clinical and Radiographic Characteristics

    Hospital records and radiographs were available for 7 of the10 patients and they were reviewed for clinical and radio-graphic characteristics of the skeletal dysplasia; no clinical orradiographic data other than the known diagnosis of MCDSwere available for the remaining 3 patients. The hospitalrecords were reviewed for data on growth, symptoms, clinicalfindings, and surgeries. The growth data was compared withpublished reference data for healthy children [Kuczmarskiet al., 2000]. A total of 109 skeletal radiographs for 7 patients(median 13 per patient) were available for review. Long-itudinal data, with two or more skeletal examinations over aminimum of 5 years, were available for four patients; crosssectional data only was available for three patients. Theradiographic surveys were most complete for the lowerlimbs since the clinical problems mainly affected the hipsand knees. All radiographs were first evaluated cross-sectionally to characterize typical features in different agegroups. Longitudinal radiographs were then used to seewhether similar sequence of changes with age occurred inindividual patients.

    Characterization of Mutations

    Blood samples were collected for DNA extraction andmutational analysis. Mutational screening of the COL10A1gene was performed by direct sequencing of five overlappingfragments covering exons 13 and their exon/intron bound-aries. In PCR reactions, genomic DNA was amplified in avolume of 20 ml using 50 ng of each primer and 1.0 U of Taqpolymerase (Qiagen) in 1 PCR buffer (67 mM Tris-HCl,pH 8.8, 6.7 mM MgCl2, 98 mM b-mercaptoethanol, 16.6 mM(NH4)2SO4, 6.7 mM EDTA, 328 mg/ml BSA, 1.5 mM of eachdNTP, and10%DMSO.ThePCRconditionswere denaturationat 948C for 20 sec, annealing at an appropriate temperaturefor 30 sec, extension at 728C for 40 sec for 40 cycles, andan additional 8 min at 728C. The reaction products wereresolved and extracted from the 1% agarose gel (EM Science).PCR fragments were directly sequenced using ThermoSequenase Cy 5 and Cy 5.5 Dye Terminator Kit (Amersham

    Biosciences) on OpenGene System (Visible Genetics) auto-mated sequencer.

    RESULTS

    Clinical Features

    The study included 10 patients (5males) ranging in age from4 to 40 years (Table I). Patients presented with progressivegrowth failure, which had its onset postnatally, usually duringthe second year of life. It usually resulted in significant shortstature (height z-score A 6505 M 20 NA NA NA 1845T>A 6149 M 17 5.6 Genua vara OT2 1844delA 62010 F 20 3.8 Genua vara OT2 2001T>G 66618 M 13 5.7 Genua valga OT2 1989C>G 66225 F 13 3.6 Genua valga OT, EPD 1783G>A 68035 M 4 NA NA NA 1771T>C 68037 F 6 NA NA NA 1851T>A 68039 M 14 NA Genua vara OT2 1860delT 62051 F 11 1.2 No No 1942G>A 680Aa, aminoacid; NA, data not available; OT, osteotomy; EPD, epiphyseodesis.

    242 Makitie et al.

  • of MCDS, which were of similar severity to those observed inpatients #2 and #9. Her height was normal up to about18 months of age but beyond 2 years age it remained below thethird centile. Her adult height of 139 cm (3.8 SDS) wasachieved at 17 years of age. Bilateral proximal femoral andhigh tibial osteotomies were undertaken at 12 years of ageand again at 17 years of age.MCDS #51, a female, was born to healthy parents. She was

    noticed to have a limp at age 4 years. At age 8 years she wasreferred to the orthopaedic clinic for evaluation of bilateral hippain and abnormal gait. She was found to have restricted hipmovements and bilateral coxa vara on radiographs. She hashad no surgeries but complained of persistent hip symptoms.Her height at age 11 years was 135 cm (1.2 SDS) andpredicted adult height 153 cm (1.6 SDS).

    Radiographic Features

    The characteristics anddistribution of radiographic findingswere very similar in all the seven patients for whom radio-graphs were available for review. However, the degree ofseverity varied between patients but in individual patients

    the degree of severity tended to be uniform at all affected sites.The changes were more marked in the weight-bearing joints,especially in the hips, and less severe in other sites.Lower limbs. In every patient, the proximal femur was

    themost severely affected site. All the patients had significant,progressive coxa vara deformity (Figs. 1 and 2), often with analmost horizontal femoral neck, sagging of the femoral headin the femoral neck and evidence of mechanical failure. Themetaphyseal changes which resulted in a short, irregular, andwide femoral neck were apparent in early infancy (as early asat 4 months of age in one patient) and tended to progress withage. The proximal femoral epiphysis was always normal inshape but it was enlarged relative to the childs age and to thewidth of the adjacent metaphysis in early childhood.The growth plates of the distal femora and proximal tibiae

    and fibulae were irregular, thickened, and flared (Fig. 3),though the changes were less marked than those seen at theproximal femora. Widening of the proximal tibia was usuallymore pronounced medially than laterally. There was varusor valgus deformity of the long bones, resulting fromasymmetric growth of both the tibia and the femur, in allpatients exceptMCDS #51, who also presented withmuch less

    Fig. 1. Radiographs of MCDS #51 show progressive coxa vara with metaphyseal irregularity ((a) 8.5 years, (b) 11 years). Metaphyseal flaring andthickening is less remarkable at the distal femora and proximal tibiae ((c) 8.5 years) and the distal radius ((d) 11 years). The spine is normal ((e) 11 years).

    Schmid Metaphyseal Chondrodysplasia 243

  • marked changes of the growth plates (Fig. 1). The secondaryossification centers were often very large (both in width and inthickness) and asymmetric but normal in contour (Fig. 3).Metaphyseal changes at the distal tibiae and fibulae weresimilar to those seen at the knee with flaring, irregularity, andthickening of the growth plates (Fig. 4). Radiographs of the feetdid not show any growth plate anomalies or other deformities.Upper limbs. The growth plates of the proximal humeri,

    distal radii, and distal ulnae were irregular and abnormallythick; usually onlymildwideningwas seen.Onlyminimal ornochanges in the growth plates of the distal humerus, proximalradius, metacarpals, and phalanges were seen; the elbow wasnormal in all patients. The metaphyseal changes were mostmarked at the distal radius and ulna (Fig. 4) but tended tobecome less severe with age. In every patient the growth plateabnormalities were less marked at the upper limb than atthe lower limb (Figs. 1 and 4). The age of appearance and thesubsequent development as well as the shape and contour ofthe secondary ossification centers were normal. Cone epi-physes were seen in none of the patients.Spine. Radiographs of the spine were available for five

    patients.All showednormal shapeand size of the vertebrae butone had mild scoliosis and two, increased lumbar lordosis.

    COL10A1 Mutations

    All 10 patients were found to have a mutation in COL10A1.Eight of the mutations consisted of a single nucleotide sub-stitution and two patients had a deletion of a nucleotide(Table I). These sequence changes were predicted to result inpremature termination of the reading frame in six patients,with resulting truncated COL10A1 polypetides of 614666amino acids. In four patients the mutation resulted in single

    amino-acid substitution (Table I). Five of thesemutations havebeen previously reported in other cohorts of MCDS and fiveof the mutations were novel (see the online Suppl. 1 at http://www.interscience.wiley.com/jpages/1552-4825/suppmat/index.html).In each patient, the remaining regions of exon 3 as well as

    exons 1 and 2 and their exon/intron boundaries did not showany anomalies on direct sequencing.

    DISCUSSION

    In this study, we report the clinical and radiographicfindings in a large cohort of patientswithMCDSand confirmedmutations in COL10A1. The clinical features of the patientswere similar to those reported previously for MCDS, char-acterized by disproportionate short