Clinical Reasoning: A 16-year-old girl with subacute weakness and sensory loss.

SECTION 1 A previously healthy 16-year-old girl developed numbness and tingling in the lower extremities that progressed over a 10-week period to the upper limbs. Two weeks prior to admission, she also developed weakness in her arms and legs, to the point of needing help getting dressed and support for walking. She denied sphincter or systemic symptoms. During the previous year, she had complained of intermittent shooting pains and tingling down her arms. Her psychiatric history was relevant for obsessive-compulsive traits and depression, and family history included autoimmune diseases in 2 sisters, an uncle, and 2 grandparents. Upon examination, higher mental functions and cranial nerves were intact. The patient had upper limb predominant quadriparesis. Muscle strength was 4/5 proximally and 3/5 distally in upper limbs and 4/5 throughout the lower limbs. Temperature and vibration sensations were mildly reduced in the upper limbs and moderately reduced in the lower limbs. Tone was increased in all limbs, and deep tendon reflexes (DTRs) were 31 in upper limbs and 41 in lower limbs. Hoffmann sign and extensor plantar responses were present bilaterally. Romberg sign was positive and the patient could not walk without support due to a combination of motor and sensory changes.