Correct!
1. Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis (ALS) is characterized by combined upper motor neuron and lower motor neuron signs. While this patient’s ascending symmetric weakness could be consistent with lower motor neuron findings, he lacks any upper motor neuron findings like hyperreflexia, spasticity, or fasciculations.
Magnetic resonance imaging of his brain was unremarkable as was analysis of his cerebral spinal fluid. A small 1 X 1 cm mildly indurated area on his left forearm was found (Figure 3). Upon further questioning without family in the room, patient admitted to recent subcutaneous injection of black tar heroin.
Figure 3. Panel A: Photograph of the area of induration on the left forearm. Panel B: close up of the area.
Given his ongoing drug use, which diagnosis is most likely? (Click on the correct answer to proceed to the fourth and final panel)