Differential Diagnosis

• Single most likely diagnosis
  • Eczema (Atopic Dermatitis): The presence of white patches on the tummy and back, red pimple-like erythema, and the fact that the white patches become red when the area gets wet are consistent with eczema. The ring-like appearance could suggest a specific type like nummular eczema, but the overall presentation fits well with atopic dermatitis, especially given the age of the child and the introduction of solids, which can sometimes trigger or exacerbate eczema.
• Other Likely diagnoses
  • Contact Dermatitis: This could explain the red erythematous lesions, especially if they are localized to areas that come into contact with specific substances (e.g., certain soaps, lotions, or foods).
  • Seborrhoeic Dermatitis: The description of white patches and red rashes, particularly on the upper lips, could suggest seborrhoeic dermatitis, which is common in infants and can present with a red, greasy rash on the scalp, face, and torso.
  • Irritant Dermatitis: Given the child's age and the recent introduction of solids, irritant dermatitis due to stool or urine coming into contact with the skin could be a possibility, especially if diaper hygiene is not optimal.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Congenital Syphilis: Although less common, congenital syphilis can present with skin rashes, among other symptoms. It's crucial to consider this in the differential diagnosis due to its severe consequences if left untreated.
  • Meningococcemia: While the child appears well, the sudden onset of a rash, particularly one that could be described as pimple-like or petechial, necessitates consideration of meningococcemia, a life-threatening condition caused by Neisseria meningitidis.
• Rare diagnoses
  • Pityriasis Alba: A condition that presents with round, oval, or irregular patches of hypopigmentation, often with slight scaling, which could fit the description of the white patches. However, it typically doesn't have the acute onset of red rashes as described.
  • Lichen Sclerosus: A rare condition in children that can cause white, patchy skin that's thinner than normal, which might fit the description of the white patches. However, it's less likely given the acute presentation and the presence of red rashes.