Joseph and Campbell described a family with hereditary vitamin B12 deficiency. The nine-year-old proband developed progressive ataxia, leg weakness, learning difficulty, and fatigue. Prior to referral he was incorrectly diagnosed with Friedreich ataxia based in part on peripheral nerve conduction velocities and electromyography findings of a sensorimotor axonal neuropathy. However, gene testing did not confirm the diagnosis, and his fatigue, cognitive symptoms, and rapid progression would be atypical of Friedreich ataxia.
Discovery of a macrocytic anemia led to the diagnosis of vitamin B12 deficiency, and genetic testing identified a mutation of the CUBN gene, one of two genes responsible for the cobalamin-intrinsic factor receptor complex in the terminal ileum. Two asymptomatic younger siblings were also affected.
All three children began monthly vitamin B12 injections. The proband improved dramatically, but his symptoms did not completely resolve, while his brothers remain asymptomatic.
The important lesson is that early treatment of vitamin deficiencies usually prevents permanent neurological impairment, while delayed treatment may not.
Pediatrics in Review is an educational journal published by the American Academy of Pediatrics.
Joseph FD, Campbell DR, Cohn S, Roach ES. A child with falls, fatigue, and dementia. Pediatr Rev 2022;43:466-468.