Kennedy disease misdiagnosed as polymyositis: a case report

BACKGROUND: Polymyositis is an immune-mediated myopathy with clinical features of proximal muscle weakness. Dysphagia and neck flexor weakness can develop along with respiratory muscle weakness as the disease progresses. Kennedy disease or X-linked spinobulbar muscular atrophy is a rare X-linked recessive disorder with clinical features of slowly progressive atrophy and weakness of limb and bulbar muscles. These two disorders may have overlapping clinical manifestations. CASE PRESENTATION: We present the case of a 52-year-old Filipino man with chronic weakness involving his proximal muscle groups who carried the diagnosis of polymyositis and was refractory to multiple immunomodulatory therapies. Further neurologic examination and history taking along with selective serologic and electrodiagnostic studies instead confirmed the diagnosis of Kennedy disease. CONCLUSIONS: Distinction between polymyositis and Kennedy disease may be difficult given the potential overlapping clinical manifestations. However, with careful neurological history taking, examination, and selective serologic plus electrodiagnostic investigations the correct diagnosis may be made, thus sparing the patient ineffective therapy. One must always be sure of the diagnosis of polymyositis before it’s classified as refractory.