Rapidly Expanding Pustular Lesion in a 12-Month-Old Infant

Case at a Glance

A 12-month-old female infant presented with a rapidly enlarging pustular lesion on the lower extremity, initially concerning for molluscum contagiosum but diagnosed as an infected pustule with risk of progression to furunculosis.

Patient's Story

The mother of a 12-month-old female infant noticed a new bump on her daughter's leg. The lesion was asymptomatic and did not appear to cause discomfort to the child. The mother reported that the lesion had visibly increased in size within hours of initial discovery, and noted the presence of a dark center within the pustule. She was unable to identify any similar insect bites or skin conditions through online research.

Initial Assessment

Physical examination revealed a solitary pustular lesion on the lower extremity with central dark material. The lesion demonstrated rapid expansion over several hours. The infant appeared otherwise well with no systemic symptoms. Initial differential diagnosis included molluscum contagiosum, insect bite reaction, or bacterial skin infection.

The Diagnostic Journey

Based on the clinical presentation of rapid expansion, pustular appearance, and central dark material, the lesion was identified as an infected pustule rather than molluscum contagiosum. The rapid growth pattern and morphology were inconsistent with typical molluscum lesions, which are typically flesh-colored papules with central umbilication.

Final Diagnosis

Infected pustule with concern for potential progression to furunculosis (boil)

Treatment Plan

Conservative management was initiated with warm compress therapy to promote drainage. Parents were advised to apply topical antibiotic ointment if drainage occurred. Close monitoring was recommended due to the infant's age and risk of bacterial spread into deeper tissues. Parents were counseled on when to seek immediate medical attention if signs of cellulitis or systemic infection developed.

Outcome and Follow-up

The family was provided with specific instructions for home care and monitoring. Given the rapid progression noted within hours and the patient's young age, urgent medical evaluation was recommended if the lesion continued to expand or if signs of surrounding cellulitis developed. The importance of preventing bacterial spread through proper hygiene measures was emphasized.