87 year old non-diabetic man presented with progressive numbness and weakness in the lower limbs for 2 years and bilateral hand weakness for 6 months. Edema was noted in the legs and hands for 6 months. He was initially diagnosed with B12 deficiency (230 pg/ml), but the symptoms deteriorated while on monthly intramuscular B12 injections. He had H/O gout attacks and was started on colchicine about one year before. Exam showed 2+ pedal edema and erythema affecting the face, trunk and upper and lower limbs (see right). Muscle strength was 2/5 in the hand interossei and ankle dorsiflexors, and 4/5 in more proximal upper and lower limbs. Reflexes were diffusely absent. There was impaired proprioception at the toes and absent vibration at the ankles and fingertips. Pinprick was diminished up to knees and elbows. Lab-work was significant for: blood glucose 85 mg/dl, Ck 85 U/L, creatinine of 1.9 mg/dl, GFR of 30 ml/min. Paraneoplastic panel showed elevated titer of voltage gated potassium channels (0.12 nmol/L, normal <0.02). TSH: 7.32 mcU/ml (H). Click here for EMG and nerve conduction study. What is the differential diagnosis? (click here)
