Differential Diagnosis for a 6-week-old Girl with a Rash
- Single most likely diagnosis
- Erythema toxicum neonatorum: This condition is a common, benign rash that appears in the first few weeks of life, characterized by small, nonblanching, erythematous maculopapular spots, which matches the patient's presentation.
- Other Likely diagnoses
- Infantile hemangioma: Although less common, infantile hemangiomas can appear as small, red spots and may be distributed over the arms and legs.
- Mongolian spots: These are benign, flat congenital melanocytic lesions that can appear as blue or blue-gray spots, but may also present as erythematous macules, especially in lighter-skinned individuals.
- Seborrheic dermatitis: This condition can cause a rash on the skin, but it typically involves the scalp, face, and diaper area, which doesn't perfectly match the patient's presentation.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed)
- Congenital infections (e.g., congenital syphilis, congenital rubella): These conditions can cause rashes and have serious consequences if left untreated.
- Meningococcemia: This is a life-threatening infection that can cause a petechial or purpuric rash, which may resemble the patient's presentation.
- Leukemia cutis: Although extremely rare in infants, leukemia cutis can cause skin lesions that may appear as a rash.
- Rare diagnoses
- Blue rubber bleb nevus syndrome: A rare condition characterized by multiple venous malformations that can appear as blue or purple spots.
- Langerhans cell histiocytosis: A rare disorder that can cause skin lesions, among other symptoms.
- Congenital cytomegalovirus infection: A rare condition that can cause a rash, among other symptoms, in newborns.