Differential Diagnosis for the 18-Month-Old Female Patient
- Single Most Likely Diagnosis
- Varicella (Chickenpox): The presence of a diffuse vesiculopustular rash with lesions at various stages of evolution, fever, and the development of cellulitis as a complication are highly suggestive of varicella. The rash's characteristic progression from vesicles to pustules and then to crusted lesions is a hallmark of this infection.
- Other Likely Diagnoses
- Impetigo: While primarily a superficial skin infection, impetigo can present with vesiculopustular lesions and can be secondary to a viral infection. However, it doesn't fully explain the systemic symptoms like fever and the widespread nature of the rash.
- Eczema Herpeticum: This is a disseminated herpes simplex virus infection that can occur in patients with atopic dermatitis, presenting with widespread vesiculopustular lesions. However, the absence of mouth lesions and the specific description of the rash make it less likely.
- Do Not Miss Diagnoses
- Staphylococcal Scalded Skin Syndrome (SSSS): Although less likely given the description, SSSS is a serious condition caused by staphylococcal toxins that can present with widespread skin lesions and fever. It's crucial to consider this diagnosis due to its potential severity and the need for specific treatment.
- Toxic Epidermal Necrolysis (TEN): A severe skin condition usually triggered by medications, TEN can present with widespread skin lesions and detachment. It's a medical emergency and, although unlikely given the context, should be considered due to its high mortality rate.
- Rare Diagnoses
- Enteroviral Infections: Certain enteroviruses can cause rash and fever, but the specific pattern of lesions and the presence of cellulitis as a complication make this a less likely diagnosis.
- Zoster (Shingles): Uncommon in this age group without a history of varicella or immunocompromise, zoster typically presents with a dermatomal rash, which doesn't fit the patient's diffuse rash description.