Sunday, July 10, 2016

Study group discussion: A case of vitamin deficiency

Here's a vignette that I found on USMLE forums:

A 20-year-old male patient is admitted to the hospital 6 months ago following a motorcycle accident resulting in a severe closed head injury. The man has experienced recurrent fungal skin infections resistant to treatment for 1 month and severe vomiting over the last 2 days. Review of the patient's records shows he was well before the injury. He now suffers severe permanent cognitive impairment and requires continuous high-dose phenytoin therapy to manage chronic debilitating tonic-clonic seizures. The patient is resting comfortably in no apparent distress. He is unable to converse coherently. Vital signs are normal. Physical exam is striking for nearly total alopecia. A periorofacial erythematous macular rash is present along with severe seborrheic dermatitis and several truncal ringlike lesions consistent with tinea corpus infection.

Select the most likely vitamin deficiency.
Answer Choices:
A. Vitamin A deficiency
B. Vitamin B12 deficiency
C. Vitamin C deficiency
D. Vitamin D deficiency
E. Vitamin E deficiency
F. Thiamine deficiency
G. Pyridoxine deficiency
H. Folate deficiency
I. Biotin deficiency

The answer is Biotin deficiency.

Symptoms of biotin deficiency develop within 3-5 weeks of the onset of deficient biotin intake. The most common cutaneous findings include the following:
Dry skin
Seborrheic dermatitis
Fungal infections
Rashes, including erythematous periorofacial macular rash
Fine and brittle hair
Hair loss or total alopecia
Approximately 1-2 weeks later, neurologic symptoms begin to develop. The most common neurologic findings include the following:
Mild depression, which may progress to profound lassitude and, eventually, to somnolence
Changes in mental status
Generalized muscular pains (myalgias)
Hyperesthesias and paresthesias
Intestinal tract symptoms also develop and most commonly include the following:
Nausea, occasionally severe

Causes of biotin deficiency include the following:

Eating raw egg whites
Some mistakenly believe that raw egg-white consumption is the only cause of biotin deficiency. Nonetheless, a diet that contains raw egg whites quickly and almost invariably leads to biotin deficiency.

Anticonvulsant therapy
Prolonged use of certain drugs, especially phenytoin, primidone, and carbamazepine, may lead to biotin deficiency; however, valproic acid therapy does not cause this condition. Some anticonvulsants inhibit biotin transport across the intestinal mucosa. Evidence suggests that these anticonvulsants accelerate biotin catabolism. Therefore, supplemental biotin, in addition to the usual minimum daily requirements, has been suggested for patients who are treated with anticonvulsants that have been linked to biotin deficiency.

Total parenteral nutrition without biotin supplementation
Several cases of biotin deficiency in patients receiving prolonged total parenteral nutrition (TPN) therapy without added biotin have been reported. Therefore, all patients receiving TPN must also receive biotin at the recommended daily dose, especially if TPN therapy is expected to last more than 1 week. All hospital pharmacies currently include biotin in TPN preparations.

Prolonged oral antibiotic therapy
Prolonged use of oral antibiotics has been associated with biotin deficiency. Alterations in the intestinal flora caused by the prolonged administration of antibiotics are presumed to be the basis for biotin deficiency.

Genetic mutation
Mikati et al reported a case of partial biotinidase deficiency (plasma biotinidase level of 1.3 nm/min/mL) in a 7-month-old boy. The boy presented with perinatal distress followed by developmental delay, hypotonia, seizures, and infantile spasms without alopecia or dermatitis. The child's neurologic symptoms abated following biotin supplementation and antiepileptic drug therapy. DNA mutational analysis revealed that the child was homozygous for a novel E64K mutation and that his mother and father were heterozygous for the novel E64K mutation. We now report 140 known mutations in the biotinidase gene (BTD) that cause biotinidase deficiency.

Ketogenic diet (high-protein, low-fat)
In a mouse model, a ketogenic diet exaggerated biotin deficiency.

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