CLINICAL BRIEF

Fibrodysplasia Ossificans Progressiva: Three Indian Patientswith Mutation in the ACVR1 Gene

Anju Shukla & Onjal Taywade & Joshi Stephen &

Divya Gupta & Shubha R. Phadke

Received: 29 August 2012 /Accepted: 27 May 2013# Dr. K C Chaudhuri Foundation 2013

Abstract Fibrodysplasia ossificans progressiva (FOP) isa rare genetic disorder characterized by ectopic boneformation involving the connective tissues leading tosevere skeletal manifestations. The genetic defect in thisdisorder has not been characterized in Indian patients tilldate. The authors report three cases of FOP along withthe molecular defects identified in them. Exon 4 of theACVR1 gene was amplified and analysed by sequencing.All three cases revealed common heterozygous mutationi.e., c.617(G>A). Identification of this mutation wouldlead to decrease in misdiagnosis and subsequent iatrogenicharm caused to these children by unnecessary surgicalprocedures. Also, mutation detection would provide anopportunity for prenatal diagnosis.

Keywords Fibrodysplasia ossificans progressiva . FOP .

Ectopic ossification . ACVR1 gene

Introduction

Fibrodysplasia ossificans progressiva (FOP; OMIM 135100)is an extremely disabling genetic disorder of the skeletalsystem with a prevalence of about 1 in 2 million. It is charac-terized by progressive development of ectopic ossification ofskeletal muscles and other connective tissues. The majority ofFOP cases are sporadic, but in few familial cases, autosomal-dominant pattern of inheritance has been observed [1]. Delayor failure in diagnosing FOP without characteristic great toe

abnormalities or with minor ectopic ossification may lead tounwanted invasive diagnostic and therapeutic procedures.

The authors report 3 cases of FOP who presented with theclinical signs and symptoms suggestive of FOP which weresubsequently confirmed by molecular methods. The moleculardefect has been described for the first time in Indian patients.The finding of similar common mutation in our typical casestoo, makes it easier to confirm the disease by molecularmethods even before the onset of heterotopic ossification andalso helps to provide prenatal diagnosis in at risk families.

Case Reports

All the index three cases were sporadic with normal parentsand typical clinical features of FOP. The first patient G, was a10 y female, presented with multiple swellings over fore-head, back and extremities which were progressively in-creasing in size since 4 y. There was history of restrictionof movement in shoulder, elbow and ankle joints along withrestricted neck and jaw movements. On examination, boththe halluces were short and deviated laterally.

Second patient S, a 4 y male, presented with swellingsover chest, back and abdomen since 2 y (Fig. 1). Thesenodules remained soft for initial 2–3 mo and later becamebony hard. There was history of restriction of movements inneck, left shoulder and left elbow joints. On examination, leftarm musculature was completely replaced by bony tissue.Both the thumbs and halluces were short since birth.

The third case A, 13 y female, too had bilateral toeabnormalities since birth (Fig. 2). She developed swellingover the left scapular region followed by swelling over thelimbs since the age of 7 y. Child had became non ambulatorysince last 1 y due to ossification of thigh muscle of left lowerlimb.

Peripheral blood samples were obtained from patientsafter an informed consent. Genomic DNAwas extracted with

A. Shukla :O. Taywade : J. Stephen :D. Gupta : S. R. Phadke (*)Department of Medical Genetics, Sanjay Gandhi Post GraduateInstitute of Medical Sciences, Rae Bareilly Road,Lucknow 226 014, Indiae-mail: shubha@sgpgi.ac.in; shubharaophadke@gmail.com

Indian J PediatrDOI 10.1007/s12098-013-1117-5

Invitrogen Kit (Carlsbad, CA) as per the manufacturer’s in-structions. The primers for exon 4 were designed usingBLAST software.

DNA sequencing reaction was set up with Dideoxy Termi-nator Cycle Sequencing Kit. The capillary electrophoresis ofthe products was performed in ABI PRISMTM 310 GENETICANALYZER (Applied Biosystems, Foster city, CA) (Fig. 3).

DNA sequencing of exon 4 of ACVR1 gene for all threecases showed common heterozygous mutation c.617(G>A)which causes an amino acid change in codon 206 fromarginine to histidine (R206H; CGC>CAC).

Discussion

The authors looked for the most common heterozygous pointmutation found worldwide in typical sporadic as well asfamilial FOP cases [2, 3]. All the patients harbored this het-erozygous mutation of c.617G>A in exon 4 of ACVR1 gene.

The primary molecular pathology in FOP involves thebone morphogenetic protein (BMP) signaling pathway. Thegene activin receptor IA (ACVR1) encodes a BMP type Ireceptor [4]. All the mutations identified till date in the

ACVR1 gene occur in the highly conserved glycine–serine(GS) or the protein kinase domain of the receptor which areresponsible for downstream signaling cascade and expres-sion of genes responsible for ossification [2].

Clinical diagnosis of FOP is based on two main criteria;malformation of the great toes and presence of heterotopicossification which usually begins in the occipital, cervicaland upper paraspinal muscles [5, 6]. Children with FOP areasymptomatic at birth except for abnormal great toes which areshort with or without valgus deviation. During the first decadeof life, they develop painful soft tissue swellings of connectivetissues, including aponeuroses, fascia, ligaments, tendons andskeletal muscles which are gradually replaced by cartilage andlater by bone as a result of endochondral ossification [7].

Before the appearance of heterotropic ossification, FOP islikely to be misdiagnosed as isolated congenital malforma-tion especially brachydactyly or congenital bunions whileafter the appearance of swelling, is commonly diagnosed assarcoma, desmoid tumor, aggressive juvenile fibromatosis orlymphedema [5]. Diagnostic errors and inappropriate medi-cal procedures, for example, attempts to remove the hetero-topic bone, may lead to exaggerated new bone formationsand can aggravate the natural history of this disease [8].Thus, early diagnosis and confirmation of FOP is essentialif such iatrogenic hazards are to be avoided.

The mutational analysis of the ACVR1 is helpful inconfirming or excluding a diagnosis of FOP in clinicallyambiguous patients. In familial cases, prenatal diagnosiscan be offered to the family if the mutation is already knownin the proband. In sporadic cases, the risk of recurrence insibs would be very low but germ line mosaicism can never beruled out in all autosomal dominant and X-linked disorders.Hence, prenatal diagnosis in these cases can be offered toreassure the family.

Conclusions

Mutation analysis of ACVR1 gene can be used for the earlyconfirmation of diagnosis of FOP. This would allow physi-cians to advice on the avoidance of provoking events, whichin turn would reduce exacerbating the disease. Also, it can

Fig. 1 Swelling due to heterotopic ossification of Patient S (arrows)

Fig. 2 Short, monophalangic great toe with valgus deformity in patient A

Fig. 3 Sequence chromatogram c.617G>A mutation in ACVR1 gene(arrow)

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confirm the diagnosis of FOP in patients with ambiguousfeatures. Prenatal diagnosis by molecular methods can alsobe offered in familial as well as sporadic cases.

Acknowledgments The authors thank Indian Council of MedicalResearch for funding the project. They also thank the patient and theirfamilies for their cooperation and support.

Conflict of Interest None.

Role of Funding Source Indian Council of Medical Research fundedthis project.

References

1. Smith R. Fibrodysplasia (myositis) ossificans progressive. Clinicallessons from a rare disease. Clin Orthop Relat Res. 1988;346:7–14.

2. Shore EM, XuM, Feldman GJ, Fenstermacher DA, Cho TJ, Choi IH,et al. A recurrent mutation in the BMP type I receptor ACVR1 causes

inherited and sporadic fibrodysplasia ossificans progressiva. NatGenet. 2006;38:525–7.

3. Kaplan FS, XuM, Seemann P, Connor JM, Glaser DL, Carroll L, et al.Classic and atypical fibrodysplasia ossificans progressiva (FOP) phe-notypes are caused by mutations in the bone morphogenetic protein(BMP) type I receptor ACVR1. Hum Mutat. 2009;30:379–90.

4. Billings PC, Fiori JL, Bentwood JL, O’Connell MP, Jiao X,Nussbaum B, et al. Dysregulated BMP signaling and enhancedosteogenic differentiation of connective tissue progenitor cells frompatients with fibrodysplasia ossificans progressiva (FOP). J BoneMiner Res. 2008;23:305–13.

5. Kaplan FS, Xu M, Glaser D, Collins F, Connor M, Kitterman J, et al.Early diagnosis of fibrodysplasia ossificans progressiva. Pediatrics.2008;121:e1295–300.

6. Cohen RB, Hahn GV, Tabas J, Peeper J, Levitz CL, Sando A, et al.The natural history of heterotopic ossification in patients who havefibrodysplasia ossificans progressiva. A study of forty-four patients.J Bone Joint Surg Am. 1993;75:215–9.

7. Connor JM, Evans DA. Fibrodysplasia ossificans progressiva. Theclinical features and natural history 34 patients. J Bone Joint Surg Br.1982;64:76–83.

8. Kaplan FS, Glaser DL, Shore EM. Fibrodysplasia (myositis) ossificansprogressiva. In: Favus MJ, ed. Primer on theMetabolic Bone Diseasesand Disorders of Mineral Metabolism. 6th ed. Washington: TheAmerican Society for Bone and Mineral Research; 2006. pp. 450–3.

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