Problem:
A previously healthy 56-year-old male presents with progressive neuropathy and declining mental status over the previous year. The patient initially developed numbness of his fingertips and the balls of his feet and began to lose motor control of his hands, which manifested as dropping objects or flinging them as he tried to pick them up. As symptoms progressed, he developed short-term memory loss and slowing of cognitive function. He states he began to "cut out meat" from his diet a few years ago for ethical reasons. Lab values are as follows.
Mean corpuscular volume (MCV)
103 fL (80-100 fL)
Serum Methylmalonic acid (MMA)
6434 nmol/L (0-400 nmol/L)
Plasma Homocysteine
31 μmol/L (5-15 μmol/L)
Q1. What vitamin deficiency or toxicity may be present?
Q2. From his history, what are two factors that led to your conclusion?
Q3. How do his lab values contribute to your diagnosis (include the reason why labs are abnormal)?
Q4. What recommendations would you make that are realistic for this patient to treat this deficiency?