To investigate the clinical features, mutation of the GNAS1 and pathogenesis of progressive osseous heteroplasia (POH).
The typical clinical, pathological and radiographic features of a boy with POH were collected and summarized following family survey. The GNAS1 gene sequence of all family members were amplified by polymerase chain reaction (PCR) and the products were sequenced directly to identify the mutations. A literature review and long-term follow up were also conducted.
The patient was an 11-year-old boy who had the onset in infancy, which indicates a chronic progressive cause of disease. The clinical features include the unsmooth local skin of the right shank where spread many rigid rice-like or irregular slabby uplifts, slabby bone-like sclerosis on the left lower mandible, left masticatory muscles, in lateral subcutaneous site of left hip joint and deep tissue, accompanied by gradually progressive difficulty in opening mouth. Histopathology showed that there were loosened hyperplasia of fibroblast and interstitial edema with punctiformed ossification. Radiographs showed flocculence hyperdense image in the subcutaneous tissues and muscles around left lower mandible, and the left masticatory muscles were obviously involved. The 3-dimensional computed tomography showed dislocations of the left temporomandibular joint. Sheeted hyperdense image with inequable density could be noted in lateral muscles of the left hip. And lamellar hyperdense image parallel to the long axis of the bone could be seen in the subcutaneous dorsum of the left foot and achilles tendon. Macro-thumb and of brachydactylia of the hands and feet were not present. The level of calcium, phosphorus and alkaline phosphatase in the blood were normal. Brother of same father but different mothers was free of the disease and no patient of the same disease was found in maternal line and paternal lines. A mutated allele in exon 7 and a polymorphism in exon 5 were found in GNAS1 gene in both of the patient and his father.
There is possibility/likelihood/probability that Chinese children could develop POH. Translocated dermal ossification began in infancy and shows a progressive cause in childhood. The disease is characterized by the heterotopic ossification of the skin, deep tissue, muscles and facial surface tissues. The location of the mutation in this study was different from that reported in abroad studies although exist in the same exons.