The hyperpigmentation (darkening) of her abdominal skin is pathognomonic (strongly suggestive) of yeast (Malassezia) infection often seen as a complication of allergic dermatitis in my patients. The reddish tinge to her haircoat can also indicate yeast but also porphyrin staining. Porphyrin is a dye found in saliva and tears.
When addressing this infection any underlying cause (allergies, endocrinopathy (hormonal disorder such as hypothyroidism), or keratinization defect (as seen with seborrhea) must be identified and corrected.
For mild cases, topical therapy alone is often effective. Maggieshould be bathed every 2-3 days with shampoo that contains 2% ketoconazole, 1% ketoconazole/2% chlorhexidine, 2% miconazole, 2% to 4% chlorhexidine, or 1% selenium disulfide. Shampoos that have two active ingredients provide better efficacy. Treatment should be continued until the lesions resolve and follow-up skin cytology (microscopic exam of a small sample of herskin surface) reveals no organisms (~4 weeks).
The treatment of choice for moderate to severe cases is ketoconazole or fluconazole at 10 mg/kg (5 mg/lb) orally with food every 24 hours. Treatment should be continued as stated above.
Alternatively, treatment with terbinafine at 5-10 mg/kg orally daily or itraconazole (Sporanox) at 5-10 mg/kg daily for a month may be effective.
The prognosis is good if the underlying cause can be identified and corrected. Otherwise, regular once- or twice-weekly antiyeast shampoo baths may be needed to prevent relapse.
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