0521779407-07 CUNY1086/Karliner 0 521 77940 7 June 4, 2007 21:10
Folic Acid/Cobalamin (Vitamin B12) Deficiency 575Folic Acid/Cobalamin (Vitamin B12) Deficiency..............
ASOK C. ANTONY, MD
history & physical
■Three-stage approach:
Recognize megaloblastic/neuropathologic manifestations of
folate/cobalamin deficiency.
Distinguish between isolated folate, cobalamin or combined defi-
ciency.
Define underlying disease/mechanism.
■Clinical manifestations of Folate/cobalamin deficiency are similar
(with notable exceptions).
■History and physical examination depend on etiology of deficiency.
Cobalamin deficiency develops insidiously (∼5–10 years to man-
ifest clinically); folate deficiency manifests within 6 months of
onset.
■Clinical Presentations: Pancytopenia with megaloblastic marrow;
congestive heart failure; beefy-red tongue; melanin pigmentation,
premature graying; infertility/sterility
Neuropsychiatric presentation (subacute combined degeneration
involving posterior, pyramidal, spinocerebellar, and spinothalamic
tracts and secondarily peripheral nerves) unique to cobalamin defi-
ciency. Dorsal tract involved earliest in >70% with paresthesias/ataxia,
diminished vibration (256 cps) and proprioception sense. Neuropathic
involvement of legs precedes arms. Clinical findings can include posi-
tive Romberg’s and Lhermitte’s sign, loss of sphincter and bowel control,
cranial nerve palsy, optic neuritis, and cortical dysfunction (dementia,
psychoses, mood disturbances).
Note: In the USA, cobalamin deficiency-related neurologic impair-
ment is often not associated with hematologic manifestations, and vice
versa. In developing countries, however, cobalamin deficiency can pre-
sent with florid pancytopenia, mild hepatosplenomegaly, fever, and thr-
ombocytopenia, with the neuropsychiatric syndrome manifesting later.
■Cobalamin Deficiency: General Mechanisms
➣Nutritional
➣Inadequate dissociation food-cobalamin complex
➣Absent intrinsic factor (IF) secretion or interaction with cobal-
amin