Osteoglophonic dysplasia
Osteoglophonic dysplasia is a rare genetic condition characterized by abnormal bone growth, severe craniofacial abnormalities, and short stature.
Overview
The term osteoglophonic refers to bones having distinctive hollowed-out areas that appear as lesions or holes on x-ray images. These lesions typically affect the long bones of the arms and legs. In people with this condition, bones in the skull often fuse together too early, a process known as craniosynostosis, which can result in a flat head appearance.
Symptoms
Characteristic features of osteoglophonic dysplasia include:
- Craniofacial abnormalities: Prominent forehead, widely spaced and prominent eyes, low-set ears, flattened nasal bridge and mid-face, protruding jaw, and a high arch in the roof of the mouth.
- Dental issues: Clinical anodontia (teeth never emerge from the jaw) and hypertrophic gingiva (overgrown gums).
- Skeletal features: Hollowed lesions in long bones (often non-ossifying fibromas), short and bowed legs and arms, overlapping toes, and short, broad hands and fingers.
- Systemic issues: Failure to thrive in infants, episodes of increased body temperature and excessive sweating, pyloric stenosis, and inguinal hernia.
While intelligence is generally not affected, individuals may experience speech delays. Respiratory problems and difficulty eating or drinking may occur due to the extent of craniofacial abnormalities.
Causes
Osteoglophonic dysplasia is caused by "gain-of-function" variants in the FGFR1 gene. This gene provides instructions for making the fibroblast growth factor receptor 1 protein, which plays a major role in skeletal development, nervous system development, and the regulation of bone growth. The altered protein promotes premature skull fusion and disrupts bone growth in the limbs. It also increases the secretion of the hormone FGF23, leading to abnormal phosphate levels that further impair bone health.
Inheritance
This condition is inherited in an autosomal dominant pattern, meaning one copy of the altered gene in each cell is sufficient to cause the disorder. Most cases result from new mutations in the gene occurring during the formation of reproductive cells or in early embryonic development, though some individuals inherit the variant from an affected parent.