Identifying DMD
Recognizing the signs
DMD is a rare and fatal neuromuscular disorder that primarily affects males.1 Patients with DMD begin experiencing muscle degeneration at birth and may show signs as early as 4 months.2,3
Some Early Signs to look for:
*Timing is approximate.
Early Diagnosis Is Crucial in DMD
Patients with DMD begin experiencing muscle degeneration at birth.2
While the first signs of DMD may appear as early as 4 months, the average age at diagnosis is between 4 and 5 years.3,4
A delay in diagnosis means some motor skills have already begun deteriorating.5
Why It Matters
Diagnosing DMD earlier will enable patients to access management options, clinical trials, and support networks earlier. It will also allow families to receive genetic counseling, which will help with carrier screening and family planning.3,4
If your patient has developmental delays, checking creatine kinase (CK) levels can help determine if a neuromuscular disorder is present.7
The National Task Force for Early Identification of Childhood Neuromuscular Disorders, the AAP,† and the AAFP‡ recommend early CK testing.3,7,8
†American Academy of Pediatrics.
‡American Academy of Family Physicians.
You Can Help Identify DMD With a Creatine Kinase (CK) Test
You Can Help Identify DMD With a Creatine Kinase (CK) Test
A CK test is a quick and often inexpensive tool4 that can potentially prevent other unnecessary testing.4
The CK test is the first step in determining whether a neuromuscular condition is causing developmental delays and muscle weakness.8
The CK test measures the amount of CK in the blood. CK is an enzyme that is found in skeletal muscle, cardiac muscle, and the brain.9 It is released from muscle cells into the blood during muscle injury.10 Elevated levels almost always indicate skeletal muscle damage and can be observed as early as at birth.4,7
Although the normal range of CK levels varies with age and gender, CK levels in DMD are typically elevated 50- to 200-fold above normal levels, as shown in the table below.4
Confirming the Diagnosis With Genetic Testing
If CK is elevated, the neuromuscular specialist will order genetic testing to determine whether DMD is the cause of your patient’s symptoms.13 A genetic test can be used to confirm that your patient has a DMD genetic mutation and to identify the specific type of mutation.10 Types of genetic tests that can be used include, but are not limited to, the following:
- Multiplex ligation-dependent probe amplification (MLPA) or array-based comparative genomic hybridization (aCGH)
These tests can identify large-scale mutations in the DMD gene, which are found in ~80% of patients. For the remaining ~20% of patients, additional genetic testing may be needed. - Next-generation sequencing (NGS)
Identifies both large- and small-scale mutations in the DMD gene. Typically, no further genetic testing is required.
In rare cases, genetic testing may be inconclusive. In these situations, the specialist may recommend a muscle biopsy to detect the presence of dystrophin.10
Decode Duchenne is a program of the patient advocacy group, Parent Project Muscular Dystrophy, that offers free genetic testing for eligible patients.
REFERENCES
1. Mendell JR, Shilling C, Leslie ND, et al. Evidence-based path to newborn screening for Duchenne muscular dystrophy. Ann Neurol. 2012;71:304-313. 2. Chen Y-W, Nagaraju K, Bakay M, et al. Early onset of inflammation and later involvement of TGF in Duchenne muscular dystrophy. Neurol. 2005;65:826–834. 3. Lurio JG, Peay HL, Mathews KD. Recognition and management of motor delay and muscle weakness in children. Am Fam Physician. 2015;91:38-44. 4. Ciafaloni E, Fox DJ, Pandya S, et al. Delayed diagnosis in Duchenne muscular dystrophy: data from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet). J Pediatr. 2009;155:380-385. 5. van Ruiten HJA, Straub V, Bushby K, Guglieri M. Improving recognition of Duchenne muscular dystrophy: a retrospective case note review. Arch Dis Child. 2014;99(12):1074-1077. 6. Glascoe FP, Dworkin PH. The role of parents in the detection of developmental and behavioral problems. Pediatrics. 1995;95:829-836. 7. National Task Force for Early Identification of Childhood Neuromuscular Disorders website. Accessed on May 4, 2021. https://childmuscleweakness.org/know-the-signs/signs-of-weakness-by-age-for-primary-care 8. Noritz GH, Murphy NA. Motor delays: early identification and evaluation. Pediatrics. 2013;131:e2016-e2027. 9. Baird MF, Graham SM, Baker JS, Bickerstaff GF. Creatine-kinase- and exercise-related muscle damage implications for muscle performance and recovery. J Nutr Metab. 2012;2012:960363. 10. Aartsma-Rus A, Ginjaar lB, Bushby K. The importance of genetic diagnosis for Duchenne muscular dystrophy. J Med Genet. 2016;53:145-151. 11. Andropoulos DB. Appendix B: Pediatric normal laboratory values. In: Gregory GA, Andropoulos DB, eds. Gregory’s Pediatric Anesthesia. 5th ed. Wiley Online Library. Accessed on September 28, 2021. https://onlinelibrary.wiley.com/doi/abs/10.1002/9781444345186.app2 12. Centers for Medicare and Medicaid Services website. Billing and coding serum phosphorus. October 5, 2021. Available at: https://www.cms.gov/medicare-coverage-database/view/article.aspx?articleId=57650 13. Birnkrant DJ, Bushby K, Bann CM, et al; for the DMD Care Considerations Working Group. Diagnosis and management of Duchenne muscular dystrophy, part 1: diagnosis, and neuromuscular, rehabilitation, endocrine, and gastrointestinal and nutritional management. Lancet Neurol. 2018;17:251-267.