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Two sibs who are double heterozygotes for achondroplasia and pseudoachondroplastic dysplasia
C G Woods1, J G Rogers, V Mayne
1Victorian Clinical Genetics Service, Murdoch Institute, Royal Children's Hospital, Parkville, Melbourne, Australia.
Insights
This study details a family with two rare skeletal dysplasias: achondroplasia and pseudoachondroplastic dysplasia. The combined genetic conditions in children led to severe complications, including brain stem compression.
Area of Science:
- Medical Genetics
- Skeletal Dysplasias
- Pediatric Orthopedics
Background:
- Achondroplasia and pseudoachondroplastic dysplasia are distinct genetic skeletal disorders.
- Understanding the inheritance patterns and phenotypic expressions of these conditions is crucial.
Observation:
- A family presented with two siblings exhibiting features of both achondroplasia and pseudoachondroplastic dysplasia.
- The parents were heterozygous for each condition, with the mother having achondroplasia and the father having pseudoachondroplastic dysplasia.
Findings:
- Children initially presented with achondroplasia but developed features of pseudoachondroplastic dysplasia by 1.5 years.
- Radiographic and clinical evaluations revealed synergistic effects of both conditions, leading to poorer growth than expected for achondroplasia alone.
- Magnetic Resonance Imaging (MRI) confirmed brain stem compression at the foramen magnum in both affected siblings.
Implications:
- This case highlights the potential for severe complications, such as brain stem compression, in individuals with compound heterozygosity for achondroplasia and pseudoachondroplastic dysplasia.
- Active screening for brain stem compression is recommended in such patients.
Abstract:
We report a family in which two sibs have both achondroplasia and pseudoachondroplastic dysplasia. The mother has achondroplasia and the father has pseudoachondroplastic dysplasia, which he had inherited from his father. Both children appeared typical of achondroplasia at birth. By 1 1/2 years they had developed a fixed lumbar kyphosis with gibbus and had additional x ray changes unusual for just achondroplasia and suggestive of pseudoachondroplastic dysplasia. Subsequently both children have shown characteristic features of both conditions and have grown less well than expected for achondroplasia. Radiographs show the striking synergistic effects of the two conditions. MRI in both sibs confirmed brain stem compression at the foramen magnum. This may be an important complication and should be actively sought in any double heterozygote.