Introduction

Silver et al₁ in 1953 and Russell₂ in 1954 described two series of children with low birth weight, asymmetry, growth retardation and characteristic facies. The term Silver- Russell syndrome (SRS) has been adopted since the 1970's and over 400 cases have been reported worldwide, although strict diagnostic criteria do not exist probably reflecting the heterogeneous etiology of the condition₃. Growth failure is the main abnormality and management is aimed at addressing this. We report the case of a young girl with SRS who also developed Perthes'disease of the left hip five years later.

Case Report

A three year old Caucasian girl was referred to the growth clinic in her local hospital because of post natal growth below the 0.4^th centile. Her birth weight was 2.1kg at 37 weeks. There were no problems in pregnancy or the neonatal period. On examination, obvious findings included a triangular face and small chin, overcrowding of the teeth in her lower jaw, clinodactyly of both little fingers and 2.5cm shortening of the right lower limb and a small right foot. There were no feeding difficulties in infancy or excessive sweating. Head circumference was normal, no café au lait spots were present and no learning difficulties were apparent. There were no other systemic abnormalities. A clinical diagnosis of SRS was made and chromosome analysis undertaken, which was normal (46XX). She was managed with a right shoe raise and nutritional support and continued to grow parallel and below the 0.4^th centile. On a routine review, now aged eight, she was noted to be limping on her left leg which had developed over several months and the limb length discrepancy was now only 2cm. Orthopaedic examination revealed 10° fixed flexion deformity of the left hip and moderate restriction of range of motion. Trendelenberg's test was positive bilaterally. Thigh foot angle and trans-malleolar axis were equal. Plain radiographs of the pelvis showed Perthes' disease suggesting involvement of the left femoral head and collapsed lateral pillar with slight extrusion of the epiphysis (figures 1,2). This was entirely new in comparison to a previous pelvic radiograph 3 years previously (which was normal). A hip Arthrogram was now performed confirming severe total head involvement (figures 3 a,b,c). However as the femoral head was still well contained within the acetabulum, a trial of conservative management was agreed at an Orthopaedic case conference at Great Ormond Street Children's hospital in London. This approach resulted in a progressive improvement in the range of motion and symptomatic improvement in the left hip over the next few months. Periodic follow up has demonstrated continued clinical and radiological improvement without operative intervention.

Figure 1

Figures 1 and 2; Anteroposterior and ‘frogs legs' views showing obvious Perthes disease affecting the left hip

Figure 2

Figure 3

Figures 3 (a,b,c) Left hip arthrograms in abduction and external rotation, abduction and adduction showing signs of Perthes

Figure 4

Figure 5

Discussion

Silver Russell syndrome is a congenital syndrome of unknown aetiology, usually sporadic and has equal sex incidence. Various patterns of inheritance and chromosomal abnormalities have been suggested, most commonly involving chromosomes 7 and 17₃. Approximately 10% of patients have uniparental disomy (UPD) of chromosome 7, which was not present in this child. It has been suggested that diagnosis should include at least 3 of the following ‘major' criteria₄: Low birth weight (? 2 standard deviations), poor postnatal growth, preservation of Occipitofrontal circumference, classic facies and general asymmetry. The child in our case has all 5 of these. Other criteria include feeding difficulties and fasting hypoglycaemia in infancy, clinodactyly of the fifth finger, genital anomalies and learning difficulties in one third₅. Management comprises a multidisciplinary approach aimed at optimizing growth with appropriate nutritional support and use of growth hormone in some. Appropriate use of occupational therapy and physical therapy also needs to be made. Overall prognosis is good, especially in this case as no learning difficulties are present. The objective in this case was to prevent severe degenerative osteoarthritis in the future and followed traditional lines for Perthes disease with success.

Legg, Calve and Perthes independently described the condition which now bears their names in 1910₆. It most commonly presents in boys aged 4-9 with unilateral limp and reduced range of hip motion and is more common in caucasians. Aetiology is unknown but predisposing factors include slipped upper femoral epiphysis, trauma, steroids, sickle crisis and developmental dysplasia of the hip (DDH)₇. The pathophysiology is widely accepted as avascular necrosis of the femoral head due to compromise of the blood supply to the proximal femoral epiphysis and plain radiology confirms the diagnosis. Treatment goals are to reduce load bearing on the femoral head and maintain it within the acetabulum. There is little consensus on the optimum treatment strategy, the options being conservative or surgical. However, it is recognized that age at presentation over 8 is associated with a worse prognosis making surgery more likely and immediate prognosis depends on the extent of deformity before treatment₈,₉,₁₀. The long term risk is of secondary osteoarthritis.

In this case Perthes disease developed several years after Silver-Russell syndrome was diagnosed raising the issue of a potentially rare association or pure coincidence. The genetic basis to Perthes disease is multifactorial and does not follow classical mendelian inheritance. Delayed skeletal maturity is a well recognized feature in Silver-Russell syndrome and is strongly associated with Perthes. Biomechanically, limb length discrepancy can result in abnormal weight bearing on one leg, potentiating stress on the femoral head. However, neither Perthes nor delayed skeletal maturity appears more common in cases of sporadic hemihypertrophy₁₁,₁₂. Indeed, isolated hemihypertrophy has been linked to neoplasia₁₃. Therefore development of Perthes for this child may have been due to a combination of excessive weight bearing on the affected leg and delayed skeletal maturity, with or without a genetic predisposition.

Correspondence to

Mr. Vishal Kakar Address: 137 South Mossley hill road Liverpool L19 9BQ United Kingdom E-mail: vkakar2000@hotmail.com Telephone: +44 151 4940942 Fax: +44 151 4940942