O′Sullivan-McLeod综合征是一组长期缓慢进行性发展、表现为上肢远端无力和萎缩的下运动神经元综合征，临床较为罕见。由于对其认识不足，该综合征诊断率低，国内鲜见报道。表现与平山病类似，但在病程、治疗和预后上均有较大差别。本文报道一例具有典型临床表现的O′Sullivan-McLeod综合征，通过该病例提高临床医师的认识，不遗漏存在治疗可能性的患者，同时也避免昂贵且存在风险、却又并非必要的治疗手段，为患者提供更为准确的预后参考。.

Atypical motor neuron disease represents a rare heterogeneous group of neurodegenerative disorders with clinical, genetic and neuroimaging features distinct from those of the classic spinal or bulbar-onset amyotrophic lateral sclerosis (ALS). O'Sullivan-McLeod syndrome represents an extremely rare lower motor neuronopathy with early adult-onset distal amyotrophy and weakness in the upper limbs with asymmetrical involvement. To add to the few case series and epidemiological and genetic studies describing this variant syndrome, our team here presents a series of seven unrelated Brazilian patients with O'Sullivan-McLeod syndrome in a detailed review of their clinical, neuroimaging, laboratory and neurophysiological findings. A male-to-female ratio of 2.5 to 1 and a mean age at onset of 34.3years was observed, with a mean time delay of 6.6years between symptom-onset and a definitive diagnosis. A positive family history was observed in one case, yet whole-exome sequencing results were negative. Neuroimaging studies were unremarkable. All cases presented with chronic denervation restricted to cervical myotomes and normal sensory nerve conduction studies. This case series, one of the largest groups of patients with O'Sullivan-McLeod syndrome reported in the literature, confirms the sporadic nature of the condition and the difficulties faced in arriving at a definite diagnosis, and also expands the age limit in late adult-onset cases.

Hirayama's disease is a rare clinical variant of amyotrophic lateral sclerosis where distal muscles are involved more compared to proximal muscles and vice-versa occurs only in 10% cases and so it is differentiated from O'Sullivan McLeod syndrome which involves only small muscles of single limb. Here, we present a case of Hirayama's disease where disease achieved a plateau after 3 years with no further progression. His electrophysiological studies, and clinical picture, and magnetic resonance imaging findings were consistent with a diagnosis of Hirayama's disease.