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Achondroplasia and nail-patella syndrome: the compound phenotype
  1. M J WRIGHT*,
  2. M C AIN*,
  3. M V CLOUGH,
  4. G A BELLUS§,
  5. O HURKO,
  1. *Greenberg Center for Skeletal Dysplasias, Johns Hopkins University, Baltimore, MD, USA
  2. †Institute of Genetic Medicine, Johns Hopkins University, Baltimore, MD, USA
  3. ‡Department of Orthopedic Surgery, Johns Hopkins University, Baltimore, MD, USA
  4. §Department of Dermatology, UCHSC, Denver, CO, USA
  5. ¶Department of Neurology, Johns Hopkins University, MD, USA
  1. Dr Wright, Department of Human Genetics, University of Newcastle upon Tyne, 19/20 Claremont Place, Newcastle upon Tyne NE2 4AA, UK, m.j.wright{at}

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Editor—Achondroplasia (MIM 100800) is one of the most common chondrodysplasias with a prevalence rate of around 1 in 26 000 live births.1 Inheritance is autosomal dominant, but in around 85% the phenotype is the result of a new mutation. Common features include disproportionate short stature with short limbs, particularly rhizomelic shortening, true megalencephaly with hydrocephalus in a minority, midface hypoplasia, a trident hand configuration, and joint hyperextensibility. Motor development delay is common owing in part to generalised mild hypotonia and in part to megalencephaly. Otitis media (OM) is a common complication with around 95% of subjects having an episode of OM at some time and over 80% requiring the insertion of PE tubes on at least one occasion. Neurological compromise can result from either stenosis of the foramen magnum usually presenting in childhood or stenosis of the thoracolumbar spine in adults. Hydrocephalus, thought to result from stenosis of the jugular foramina, requires the insertion of ventriculoperitoneal shunts in approximately 10% of cases; however, benign ventriculomegaly is a common finding. Bowing of the legs with proximal and distal tibial varus is common but is often asymptomatic. Cognitive function is normal.2 In 1994 specific mutations in theFGFR3 gene were found to cause achondroplasia.3 4

Nail-patella syndrome (MIM 161200) (NPS) is an autosomal dominant disorder characterised by dysplasia of the nails, hypoplastic or absent patellae, and dysplasia of the elbow, with nephropathy in around 30% of cases. Iliac horns are not always observed but are a pathognomonic radiographic sign when present. Cognitive function is again normal. Recently, loss of function mutations in theLMX1B gene were found in patients with nail-patella syndrome.5 6

We report the case of a child, born to unaffected parents, with phenotypic features of both achondroplasia and NPS. De novo heterozygous mutations were …

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