Fast Five Quiz: Spinal Muscular Atrophy Clinical Presentation

Stephen L. Nelson, Jr, MD, PhD


February 01, 2021

Davidenkow syndrome is a form of scapuloperoneal SMA that is characterized by distal sensory loss and fasciculations, weakness of the pectoral girdle and distal leg muscles, and talipes equinovarus. Both autosomal dominant and autosomal recessive forms have been described. The clinical course is slow in the autosomal dominant form; the course of the autosomal recessive form is unknown.

Patients with X-lined recessive bulbospinal muscular atrophy (Kennedy disease) have bulbar weakness, gynecomastia, and lower motor neuron weakness that begins between the ages of 20 and 40 years. Muscles cramps frequently precede weakness, and facial and perioral fasciculations are seen in more than 90% of patients. Increased rates of type 2 diabetes, infertility, and hand tremor are associated with Kennedy disease.

Oculopharyngeal SMA is typically seen in people of French-Canadian descent. It is characterized by bulbar and cranial-nerve weakness; myopathic weakness of the limbs ensues. The pattern of inheritance is autosomal dominant with variable penetrance. The disease appears in most patients in the fourth to fifth decades of life, and it is slowly progressive.

Scapulohumeral SMA is an autosomal dominant disorder that is characterized by the onset of scapulohumeral weakness and atrophy between the fourth and sixth decades of life. The disease progresses rapidly, and death from respiratory failure occurs within 3 years.

Learn more about the clinical presentation of SMA variants.

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