Rare Dermatologic Cases: Cutaneous Prototecosis and Neutrophilic Figurative Erythema of Infancy

Conclusions

• Early biopsy and fungal/algal stains are important when a facial dermatitis or pruritic eruption is atypical and does not respond to steroid or rosacea treatment.
• Cutaneous protothecosis should be considered in chronic scaly facial eruptions, especially because it can closely mimic rosacea or nonspecific dermatitis and is often diagnosed late.
• Protothecosis is an uncommon environmental infection caused by achlorophyllous algae, most often Prototheca wickerhamii, and histology showing morula- or soccer-ball-like sporangia is diagnostic.
• Because protothecosis can be associated with immunosuppression or dissemination, patients should be evaluated for underlying immunodeficiency and systemic spread rather than assuming disease is only local.
• Localized cutaneous protothecosis is usually treated with oral azoles, most often itraconazole, while amphotericin B or other antifungals may be needed for refractory or disseminated disease and treatment may take weeks to months.
• Prognosis for localized cutaneous protothecosis is generally good, but disseminated disease and some species such as P. zopfii have worse outcomes.
• Neutrophilic figurate erythema of infancy is a rare, benign, self-limited variant of annular erythema of infancy that usually presents in early infancy with waxing and waning annular plaques.
• NFEI is characterized histologically by a dense neutrophil-rich infiltrate without true vasculitis, which makes it an important mimic of vasculitis, neonatal lupus, and other neutrophilic dermatoses.
• The main management of NFEI is reassurance and clinical follow-up rather than systemic therapy, since lesions usually resolve spontaneously without scarring.
• When evaluating NFEI, serious mimics should be excluded with appropriate workup such as ANA testing and CBC, but the condition itself is typically not associated with significant systemic symptoms.