Osteopathia Striata With Cranial Sclerosis: Clinical, Radiological, and Bone Histological Findings in an Adolescent Girl

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1 American Journal of Medical Genetics 129A:8 12 (2004) Osteopathia Striata With Cranial Sclerosis: Clinical, Radiological, and Bone Histological Findings in an Adolescent Girl L.M. Ward, 1,2 * F. Rauch, 2 R. Travers, 2 M. Roy, 3 J. Montes, 4 G. Chabot, 2,3 and F.H. Glorieux 2,4 1 Department of Pediatrics, Children s Hospital of Eastern Ontario, University of Ottawa, Ottawa, Canada 2 Genetics Unit, Shriners Hospital, McGill University, Montréal, Québec, Canada 3 Département de Pédiatrie, Hôpital Ste. Justine, Université de Montréal, Québec, Canada 4 Departments of Surgery and Pediatrics, McGill University, Montréal, Québec, Canada Osteopathia striata with cranial sclerosis (OS CS) is a rare skeletal dysplasia characterized by linear striations of the long bones, osteosclerosis of the cranium, and extra-skeletal anomalies. We provide a comprehensive description of the skeletal phenotype in a French-Canadian girl with a moderate to severe form of sporadic OS CS. Multiple medical problems, including anal stenosis and the Pierre Robin sequence, were evident in the first few years of life. At 14 years, she was fully mobile, with normal intellect and stature. She suffered chronic lower extremity pain in the absence of fractures, as well as severe headaches, unilateral facial paralysis, and bilateral mixed hearing loss. Biochemical indices of bone and mineral metabolism were within normal limits. Bone densitometry showed increased areal bone mineral density in the skull, trunk, and pelvis, but not in the upper and lower extremities. An iliac bone biopsy specimen revealed an increased amount of trabecular bone. Trabeculae were abnormally thick, but there was no evidence of disturbed bone remodeling. In a cranial bone specimen, multiple layers of periosteal bone were found that covered a compact cortical compartment containing tightly packed haversian canals. Bone lamellation was normal in both the iliac and skull samples. Osteoclast differentiation studies showed that peripheral blood osteoclast precursors from this patient formed functional osteoclasts in vitro. Thus, studies of bone metabolism did not explain why bone mass is increased in most skeletal areas of this patient. Cranial histology points to exuberant periosteal bone formation as a potential cause of the cranial sclerosis. ß 2004 Wiley-Liss, Inc. KEY WORDS: osteopathia striata; cranial sclerosis; osteosclerosis; histology Grant sponsor: Shriners of North America. *Correspondence to: L.M. Ward, M.D., Department of Pediatrics, University of Ottawa, Children s Hospital of Eastern Ont., 401 Smyth Road, Ottawa, Ontario, Canada K1H 8L1. ward_l@cheo.on.ca Received 18 September 2003; Accepted 16 December 2003 DOI /ajmg.a INTRODUCTION Osteopathia striata with cranial sclerosis (OS CS; MIM# ) is a rare skeletal dysplasia characterized by longitudinal striations of the long bone diametaphyses and sclerosis of the cranial vault and base. Striated metaphyses were first described by the Dutch radiologist Voorhoeve [1924], and their association with cranial sclerosis was subsequently reported by Hurt [1953]. OS CS can occur in isolation, or may be part of a syndrome together with heart defects, malrotation of the abdominal organs, omphalocele, partial agenesis of the corpus callosum, and the Pierre Robin sequence [Winter et al., 1980; Pellegrino et al., 1997]. Over 100 cases of OS CS have been described to date [Savarirayan et al., 1997; Bueno et al., 1998; Lazar et al., 1999; Behninger and Rott, 2000; Viot et al., 2002]. About one third of cases are sporadic, while the remainder show familial clustering. Reports of familial OS CS clearly point to dominant heritability [Horan and Beighton, 1978], but whether the trait is transmitted in an autosomal or X-linked dominant fashion remains unsettled [Behninger and Rott, 2000; Viot et al., 2002]. The linear striations of the long bones typically first appear between 5 months and 6 years of age [Viot et al., 2002] and usually are of little clinical significance. However, the cranial sclerosis is frequently disabling, as it may lead to hearing loss and nerve palsies [Behninger and Rott, 2000], and macrocephaly is often present [Viot et al., 2002]. The histological basis of the long bone striations and the skull sclerosis is not entirely clear. Increased trabecular thickness was described in the femur of a newborn, as well as in the ilium and rib of two middle-aged men [Hurt, 1953; Winter et al., 1980; Nakamura et al., 1998]. The normal lamellar pattern of mature bone was reported to be absent in one case [Nakamura et al., 1998]. In the present report, we provide a detailed analysis of the skeletal phenotype in an adolescent girl with moderately severe, sporadic OS CS. MATERIALS AND METHODS Serum and urine biochemistry was performed using methodology described previously [Ward et al., 2002]. Total body bone densitometry in the antero-posterior direction was performed using a Hologic 4500A device (Hologic, Inc., Waltham, MA). Areal bone mineral density (abmd) results were transformed to age-specific z-scores using published reference data [Bailey et al., 1996]. An iliac bone biopsy was obtained after tetracycline labeling and was processed as previously described [Glorieux et al., 2000]. Quantitative histomorphometric results were compared with previously published reference material [Glorieux et al., 2000]. A full-thickness trans-parietal bone biopsy sample was taken at the time of intracranial pressure monitoring. This specimen was compared to that of an 8-year-old boy undergoing ß 2004 Wiley-Liss, Inc.

2 Bone Histology in Osteopathia Striata 9 Fig. 1. a: Anterior posterior view of the lower extremities showing striated diametaphyses in the patient (13.8 years) with osteopathia striata with cranial sclerosis (OS CS). b: Lateral view of the cranium showing severe sclerosis in the 14.8 year old girl with OS CS. brain surgery for astrocytoma, who had no evidence of a skeletal disorder. Functional osteoclast studies were performed following isolation of peripheral blood mononuclear cells as previously described [Shalhoub et al., 2000]. Patient and control cells were plated on bone slices in triplicate. Cultures were fed every other day with colony-stimulating factor-1 (30 ng/ml) plus osteoprotegerin ligand (100 ng/ml), or colony-stimulating factor-1 (30 ng/ml) alone, for 24 days. The ability of monocyte precursors in this conditioned media to form tartrate-resistant acid phosphatase (TRAP) positive multi-nucleated osteoclasts that produced resorption lacunae in bone was evaluated. CLINICAL REPORT The proposita is of French-Canadian descent, the youngest of three daughters born to healthy, non-consanguineous parents. The extended family history was negative for skeletal disorders, miscarriages, or neonatal deaths. Delivery was spontaneous at 43 weeks gestation, following an uneventful pregnancy. Birth weight was 4.8 kg, length 55 cm, and occipital frontal circumference 40 cm, all of which were significantly greater than the 95th centile. Abnormalities noted shortly after birth included the Pierre Robin sequence (hypoplastic mandible and midline cleft palate), laryngotracheomalacia, and anal stenosis. The clinical course in the first year of life was complicated by laryngotracheal stenosis and gastroesophageal reflux with a hiatal hernia, necessitating surgical intervention. Hearing aids were prescribed at 4 (right) and 6 (left) years of age for bilateral, mixed hearing loss that was predominantly conductive. A skeletal survey obtained at the age of 4 years showed linear striations in the metaphyseal and diaphyseal areas of long bones (Fig. 1a) as well as sclerosis of the cranial base (Fig. 1b). These findings led to the diagnosis of OS CS. In retrospect, striations of the proximal humeri had already been visible on chest X-rays that had been taken at 7 months of age. The striations had not been clearly visible at 2 and 4 months of age, however (Fig. 2). At 12 years of age, complete left facial paralysis occurred, but improved following treatment with a non-steroidal anti-inflammatory agent. The patient complained of chronic lower extremity pain, especially of the hips and the knees, but had never sustained any fractures. Fig. 2. a d: Radiographs performed to assess the patient s respiratory status at various intervals, showing absence of visible abnormality of the humerus at 2 months (a). At 4 months (b), minimal, non-specific sclerosis is evident. Definite linear striations are seen at 7 months (c) and 3.6 years (d).

3 10 Ward et al. At her most recent clinical evaluation (age 14.5 years), the patient was fully mobile with normal intellectual development. The height and weight are presented in Table I. The head circumference was 62.5 cm (5 cm above the 98th centile). There was turricephaly with bifrontal bossing. The ears were small and low-set. Bilateral pre-auricular sinuses were present. Mild, left-sided facial paralysis was still evident. The palate was high-arched with significant dental crowding. The laryngotracheomalacia of childhood had resolved, and pubertal development was normal (Tanner stage 3). Her most significant complaint was headaches, which were only partially responsive to anti-inflammatory medication. Because of the persistent headaches, the patient underwent intracranial pressure monitoring, which showed no abnormality. At 14.5 years of age, a series of investigations were undertaken in order to fully characterize her skeletal phenotype and to investigate her chronic limb pain and headaches. RESULTS A biochemical evaluation of bone and mineral metabolism including serum levels of total calcium, inorganic phosphate, alkaline phosphatase, tartrate-resistant acid phosphatase (TRAP), osteocalcin, parathyroid hormone, 1,25-dihydroxyvitamin D and 25-hydroxyvitamin D levels as well as urinary excretion of calcium, cyclic adenosine-monophosphate and N- terminal telopeptide of collagen type I did not reveal any abnormality. Longitudinal striations were visible in the metaphyseal and diaphyseal regions of long bones (Fig. 1a) and fan-like TABLE I. Anthropometry and Bone Densitometry Results Parameter Result Z score Height (cm) Weight (kg) abmd (g/cm 2 ) Total body Head Upper limbs Trunk Pelvis Lower limbs abmd, areal bone mineral density. striations were evident in the ilial wings. Mild curvatures of the thoracic (dextroconvex 118) and lumbar (levoconvex 158) spine were present. There was marked craniofacial sclerosis, particularly at the skull base (Fig. 1b), which was evident at seven weeks of age. Cerebral computed tomography showed no evidence of cranial nerve entrapment despite the marked cranial sclerosis. Bone densitometry demonstrated an elevated abmd of the total body (Table I). However, abmd varied considerably between skeletal regions. There was marked elevation of skull abmd. Results for the trunk and pelvis were also elevated considering the short stature of the patient, while upper and lower limb abmd appeared to be adequate (Table I). Qualitative evaluation of the iliac bone biopsy specimen revealed increased trabecular thickness (Fig. 3a,b) and a Fig. 3. a, b: Qualitative histomorphometry at the iliac crest showing increased trabecular thickness in the patient (a) compared to an age-matched control (b). c, d: Iliac crest specimen showing a preserved pattern of lamellation under birefringent light in the proposita (c), similar to the age-matched control (d).

4 TABLE II. Iliac Bone Histomorphometry Parameter Patient Reference ranges a Structural parameters Cortical width (mm) 1, Bone volume/tissue volume (%) Trabecular thickness (mm) Trabecular Number (/mm) Formation parameters Osteoid thickness (mm) Osteoid surface/bone surface (%) Mineralizing surface/bone surface (%) Mineral apposition rate (mm/day) Bone formation rate/bone surface (mm 3 /mm 2 /year) Resorption parameters Eroded surface/bone surface (%) Osteoclast surface/bone surface (%) a Values are means and SD, according to normative data by Glorieux et al. [2000]. Bone Histology in Osteopathia Striata 11 normal pattern of birefringence under polarized light (Fig. 3c,d). Tetracycline labels were distinctly visible (not shown). Quantitative histomorphometry (Table II) showed normal cortical width. However, trabecular bone volume was markedly elevated, due to increased trabecular thickness. Histomorphometric parameters of bone formation and resorption were within normal limits. Qualitative evaluation of the cranial biopsy (Fig. 4a,b) showed layers of periosteal bone covering a compact cortical compartment with tightly packed haversian canals. The periosteal bone layers were much more evident in the proposita than in a control sample (Fig. 4c,d). There was no evidence of woven bone in the skull bone sample. Given the osteosclerosis in this patient, we evaluated osteoclast differentiation and function in vitro. Patient and control peripheral blood mononuclear cells were similarly able to form TRAP-positive multi-nucleated osteoclasts that produced resorption lacunae over the bone surface. Fig. 4. a, b: Cranial specimen showing compact cortical bone in the proposita with tightly packed Haversian canals (a) compared to an 8-year-old boy with a normal metabolic bone status (b). c, d: Cranial specimen showing successive layering of periosteal apposition (c) that is more evident compared to the control specimen (d).

5 12 Ward et al. DISCUSSION The girl described here had typical features of OS CS associated with multiple developmental anomalies. Most features of her disease have been previously associated with this skeletal dysplasia [Winter et al., 1980; Konig et al., 1996]. However, the anal stenosis found in our patient appears to be rarely associated with OS CS, as only one similar case has been published [Savarirayan et al., 1997]. Also, unusual macrosomia was noted in our patient at birth, which did not persist post-natally. A similar growth pattern has been previously described in a girl with sporadic OS CS [Kondoh et al., 2001]. Our patient s most troubling clinical feature was cranial stenosis, which has led to unilateral facial nerve paralysis and headaches. Medical imaging and intracranial monitoring have ruled out cranial nerve entrapment and hydrocephalus as causative factors. It is possible, however, that vascular entrapment is at play. As to the skeletal phenotype, bone densitometry confirmed the presence of marked cranial osteosclerosis in our patient. Elevated bone density was also found in the pelvis and trunk, but not in the upper and lower extremities. As such, there was evidence of variability in the bone density distribution. Organization of the bone matrix appeared to be normal, since the normal lamellar pattern was preserved in both iliac and cranial bone. Thus, in contrast to the report of Nakamura et al. [1998], there was no evidence of woven bone. The cranial specimen, however, showed a large number of periosteal bone layers that covered a compact cortical compartment, suggesting that the marked cranial sclerosis may have resulted from the periosteal apposition of successive bone layers. Quantitative analyses of the iliac sample revealed an increased amount of trabecular bone, which is in accordance with the elevated bone density reading and confirms previous histological reports [Hurt, 1953; Winter et al., 1980; Nakamura et al., 1998]. Nevertheless, histomorphometric indicators of bone metabolism were within normal limits. Biochemical studies also revealed a normal profile for parameters of bone and mineral metabolism, similar to previous reports [Whyte et al., 1978]. Finally, our osteoclast differentiation studies showed that peripheral blood osteoclast precursors of this patient formed functional osteoclasts in vitro. Thus, neither clinical nor in vitro studies of bone metabolism provide a clue as to why bone mass is increased in most skeletal areas of our patient. However, it must be acknowledged that small changes in bone remodeling balance can lead to large changes in bone mass [Parfitt et al., 2000]. Subtle alterations in bone metabolism may not have been detectable with the methods used. This adolescent girl with sporadic OS CS had generalized osteosclerosis with relative sparing of the limbs. Biochemical, histomorphometric, and in vitro osteoclast assays did not reveal any abnormality that could explain the osteosclerosis. Cranial histology points to exuberant periosteal bone formation as a potential cause of the cranial sclerosis. ACKNOWLEDGMENTS We thank Victoria Shalhoub (Amgen, California, USA) for performing the in vitro osteoclast studies, and the following individuals at the Shriners Hospital for Children, Montréal, Québec, Canada: Mark Lepik and Guylain Bedard for artwork and figures, Guy Charette for processing of the bone histology specimens, and Josée Depot for the biochemical studies and histomorphometric analyses. REFERENCES Bailey DA, Faulkner RA, McKay HA Growth, physical activity, and bone mineral acquisition. 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