Differentials
Dermatitis
SIGNS / SYMPTOMS
Causes include atopic dermatitis, contact dermatitis, seborrheic dermatitis, drug eruptions, Hartnup disease, lupus erythematosus, porphyria cutanea tarda, and pemphigus.
The dermatitis of pellagra is a symmetrical, bilateral and well-defined erythematous rash on exposed areas of skin sensitive to sunlight, similar in appearance to sunburn.[81]
INVESTIGATIONS
Allergy/patch testing: may reveal reactivity to allergens in atopic and contact dermatitis.
Serum IgE levels: elevated in atopic dermatitis.
Neutral aminoaciduria: >5 times the upper limit of normal range in Hartnup disease.
Antinuclear antibodies: positive in lupus erythematosus, but not specific for the condition.
Anti-double-stranded DNA and anti-Smith antibodies: may be positive in lupus erythematosus, and highly specific for the condition.
Plasma and urinary total porphyrins: elevated in porphyria cutanea tarda.
Skin biopsy: characteristic changes in the epidermal, dermal, and basal cells present in pemphigus.
Urinary metabolites of niacin (N-methyl-nicotinamide and 40% to 60% as N-methyl-2-pyridone-5-carboxamide): normal levels.
Diarrhea
SIGNS / SYMPTOMS
Characterized by the frequent evacuation of liquid stool, accompanied by an excess loss of fluid and electrolytes, especially sodium and potassium. Diarrhea can be osmotic, secretory, exudative, malabsorptive, or medication-induced.
Absence of dermatitic cutaneous lesions.
INVESTIGATIONS
Stool exam: may be positive for parasites, infection, or malabsorption.
Urinary metabolites of niacin (N-methyl-nicotinamide and 40% to 60% as N-methyl-2-pyridone-5-carboxamide): normal levels.
Dementia
SIGNS / SYMPTOMS
Loss of memory and other intellectual functions due to chronic progressive degenerative disease of the brain such as Alzheimer disease.
Absence of dermatitic cutaneous lesions.
INVESTIGATIONS
Neuropsychiatric testing (including mental state exam): may show evidence of dementia.
Urinary metabolites of niacin (N-methyl-nicotinamide and 40% to 60% as N-methyl-2-pyridone-5-carboxamide): normal levels.
Riboflavin (vitamin B2) deficiency
SIGNS / SYMPTOMS
Diet deficient in vitamin B2 causes similar symptoms to vitamin B3 deficiency. Clinical features include sore, burning lips and tongue; cheilosis and angular stomatitis; glossitis and magenta/purple tongue; seborrheic dermatitis of nasolabial folds, scrotum, and vulva; photophobia; and anemia.
INVESTIGATIONS
Percentage of flavin adenine dinucleotide needed to activate RBC enzyme glutathionine reductase: percentage stimulation index >40% indicates riboflavin deficiency.
Riboflavin coefficient: elevated.
Urinary metabolites of niacin (N-methyl-nicotinamide and 40% to 60% as N-methyl-2-pyridone-5-carboxamide): normal levels.
Pyridoxine (vitamin B6) deficiency
SIGNS / SYMPTOMS
Diet deficient in vitamin B6, consumption of Kombucha tea, or history of a medication known to interfere with vitamin B6 metabolism such as isoniazid or 5-fluorouracil.
Causes similar symptoms to vitamin B3 deficiency. Clinical features include weakness, cheilosis, glossitis, stomatitis, and peripheral neuropathy.
INVESTIGATIONS
Serum pyridoxal-5-phosphate: low.
Urinary metabolites of niacin (N-methyl-nicotinamide and 40% to 60% as N-methyl-2-pyridone-5-carboxamide): normal levels.
Peripheral neuropathy
SIGNS / SYMPTOMS
Nutritional polyneuropathies: for example, vitamin B12 deficiency.
Neuropathic signs of pellagra are difficult to distinguish from other types of polyneuropathy.
INVESTIGATIONS
Serum cyanocobalamin: low in vitamin B12 deficiency.
CBC: macrocytic anemia in vitamin B12 deficiency.
Urinary metabolites of niacin (N-methyl-nicotinamide and 40% to 60% as N-methyl-2-pyridone-5-carboxamide): normal levels.
Depression
SIGNS / SYMPTOMS
Diagnosed clinically if >5 symptoms are present over a 2-week period and represent a change from previous functioning. Symptoms include: anhedonia, changes in libido, weight changes, sleep disturbance, low energy, depressed mood, excessive guilt or feelings of worthlessness, suicidal thoughts, and poor concentration or indecisiveness.
Absence of dermatitic cutaneous lesions.
INVESTIGATIONS
Clinical diagnosis with no differentiating tests.
Urinary metabolites of niacin (N-methyl-nicotinamide and 40% to 60% as N-methyl-2-pyridone-5-carboxamide): normal levels.
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