This message is posted to help the community understand the diagnostic odyssey faced by Ryan B, a young man who was diagnosed with muscular dystrophy long before genetic testing was reliable enough to identify the specific cause of his muscle weakness. With today’s fast-breaking PR announcements, promising medical advances to treat many forms of muscular dystrophy are being discussed at a dizzying pace. It is challenging for families to sort through the hype and excitement to determine which breakthroughs are most relevant. As this story shares, it is important for patients and their families to look critically at these opportunities and to really understand what hoped-for advances in Duchenne/Becker can mean for each individual.
Ryan is a 25 year-old male with a previously unconfirmed diagnosis of Duchenne muscular dystrophy. His diagnostic journey began with a muscle biopsy in 1989, following a high CPK and history of proximal muscle weakness. The muscle biopsy did not test the dystrophin protein, and instead noted tissue changes visible by electron microscopy that were associated with Duchenne muscular dystrophy. These tissue changes are not specific to Duchenne muscular dystrophy, and therefore, are not diagnostic. Molecular genetic (DNA) testing in 1994, tested 17 of the 79 exons of the dystrophin gene plus the promoter for deletions, however, no deletions were found.
A couple of years ago, Ryan had a series of mesenchymal stem cell transplants in Puerto Rico, reportedly using two unrelated umbilical cord donors and cells from his sister. Following Ryan’s investigational therapy treatments, another muscle biopsy was performed in 2009. This time the dystrophin protein was tested, and the dystrophin protein was found to be normal. Based on the information available, one wonders, was the diagnosis ever Duchenne? And if so, did the therapy provide benefit? Because dystrophin was not previously tested, there are no pre-treatment dystrophin levels to compare to the post-treatment level. Stated another way, it cannot be determined whether there was an increase in dystrophin protein as a result of the transplants or whether the amount of dystrophin protein was always normal.
In order to address the question of diagnosis, DuchenneConnect helped guide Ryan and his family through diagnostic testing. For Ryan, testing was two-fold: To investigate whether the diagnosis was Duchenne, comprehensive molecular (DNA) testing was suggested because it had not been performed earlier. To investigate whether another form of muscular dystrophy might be the cause of Ryan’s symptoms, staining of the 2009 muscle biopsy (the only muscle tissue available) was suggested for other muscular-dystrophy related proteins.
Ryan’s comprehensive molecular testing began with testing all exons for deletions and duplications. No deletion or duplication was found, and therefore gene sequence analysis was obtained, the second step in the genetic test pathway for Duchenne. Given Ryan’s history of investigational stem cell transplants, an additional step (comparative loci analysis) was taken to verify that the lab was testing Ryan’s DNA, using markers in his DNA compared to his family members, rather than DNA originating from the donor stem cells. No dystrophin gene mutation was identified using comprehensive testing, and no donor DNA was present from Ryan’s stem cell transplants (meaning the lab was looking at Ryan’s DNA, not the donors’ DNA). As all testing for dystrophin was normal, our attention turned to testing for other forms of muscular dystrophy.
Immunostaining of the muscle tissue was performed to test other muscular dystrophy-related proteins. Dystrophin again appeared to be normal. The results for two proteins suggested other causes of muscular dystrophy, rather than Duchenne: The alpha-dystroglycan protein appeared reduced, as was the collagen VI protein. Reduced staining of the alpha-dystroglycan protein is associated with dystroglycanopathy forms of muscular dystrophy such as limb-girdle muscular dystrophy. Reduced staining of the collagen VI protein is associated with Ullrich congenital muscular dystrophy.
The next step to confirm Ryan’s diagnosis involves referral to a neurologist experienced in muscular dystrophy to correlated Ryan’s physical symptoms with the protein staining results. Ullrich congenital muscular dystrophy often involves severe weakness noted soon after birth. Most people are not able to walk independently and develop contractures of joints (knee, elbow, e.g.) that further restrict movement. Skin changes are often noticed as well. For these reasons, Ullrich congenital muscular dystrophy may not resemble Duchenne. There are many forms of limb-girdle muscular dystrophy, some of which very closely resemble Duchenne muscular dystrophy, in contrast to Ullrich. Limb-girdle muscular dystrophy type 2I, for example, has variable ages of onset of proximal muscle weakness, calf hypertrophy and may have a strongly Duchenne-like course of disease. Further molecular (DNA) genetic testing is available to test for mutations in genes that cause limb-girdle muscular dystrophy as well as Ullrich congenital muscular dystrophy.
At the time of this blog post, Ryan has been referred to neurologists who specialize in diagnosis and care of limb-girdle muscular dystrophy to explore additional genetic tests and shed light on this puzzling diagnostic journey.