Coinheritance of Noonan syndrome and Becker muscular dystrophy

We describe for the first time a case of a 9-year old boy with co-existence of dystrophinopathy and Noonan syndrome (NS). Although the patient has a severe muscular clinical phenotype, consistent with Duchenne muscular dystrophy (DMD), the diagnosis of Becker muscular dystrophy (BMD) was proposed based on family history (brother with BMD) and confirmed by muscle immunohistochemistry, and molecular study shown an in-frame DMD gene mutation. The patient also fulfilled the clinical criteria of NS and he harbors a hotspot mutation on PTPN11 gene. This genetic combination may be an explanation for the variability of clinical expression in the family.