We at Curious Cranium would like to wish everyone a Happy Doctors’ Day and would like to share with you guys an exceptional case today.
A 25-year-old male patient presents to the Ortho-OPD due to chronic bilateral lower extremity pain and joint stiffness. On examination is tenderness to palpation of the lower extremities—two hyperpigmented spots with ragged edges on the lumbar region. Past Hx is significant for multiple fractures. The X-ray of the lower extremity is shown below. Family history is negative. What is the diagnosis? What’s the mechanism behind the radiological finding?
Picture courtesy - Dr. Varun Lakhmani
Disclaimer: Permission to take the picture was taken from the patient…
This is a case of McCune-Albright Syndrome.
It is a rare genetic disorder characterized by polyostotic fibrous dysplasia, café-au-lait spots and endocrinopathy (presenting as precocious puberty, gigantism, cushing’s syndrome).
There is an activating mutation in GNAS1 on chromosome 20, leading to constitutive receptor signaling and inappropriate production of excess cAMP. McCune-Albright syndrome is not inherited. Instead, it is caused by a random mutation in the GNAS gene that occurs very early in development. As a result, some of the body’s cells have a normal version of the GNAS gene, while other cells have the mutated version.
Radiological findings - patchy areas of lytic bone lesions and sclerosis, more commonly in the metaphyseal and diaphyseal regions. Trabeculated lesions with a ground-glass appearance may be found.
Diagnosis – molecular testing for GNAS1 analysis.
DDx – Neurofibromatosis type I (has neurologic involvement and a family history of café-au-lait spots)
Tx – There are no specific treatments for McCune-Albright syndrome