Differential Diagnosis for a 3-year-old with Mouth Ulcer and Hand Ulcer after Chicken Pox

Single Most Likely Diagnosis

• Chicken Pox Complications or Secondary Infections: Given the recent history of chicken pox, it's plausible that the ulcers are a result of secondary bacterial infections, which are common complications following varicella infections. The timing (unwell since 15 days) fits with the typical timeframe for such complications to arise.

Other Likely Diagnoses

• Herpetic Gingivostomatitis: This condition, caused by the herpes simplex virus, can lead to mouth ulcers and could potentially spread to the hands, especially in young children who may not have good hygiene practices. The recent illness could be unrelated or a trigger.
• Hand, Foot, and Mouth Disease (HFMD): Although HFMD typically presents with lesions on the hands and feet, and sometimes in the mouth, it's a possibility, especially if the child has been exposed to other children with the disease. The recent chicken pox could be a coincidence.
• Impetigo: A highly contagious skin infection that can cause sores or ulcers on the hands and potentially around the mouth if the infection spreads. This could be a secondary infection following the chicken pox.

Do Not Miss Diagnoses

• Eczema Herpeticum: A serious condition that occurs when the herpes simplex virus infects the skin of individuals with atopic dermatitis (eczema). It requires prompt treatment to prevent serious complications.
• Staphylococcal Scalded Skin Syndrome (SSSS): A condition caused by staphylococcal toxins that can lead to widespread skin lesions and ulcers. It's more common in children and can be life-threatening if not treated promptly.
• Steven-Johnson Syndrome (SJS) or Toxic Epidermal Necrolysis (TEN): Although rare, these are severe skin conditions usually triggered by medications or infections. They can present with skin ulcers and detachment and are medical emergencies.

Rare Diagnoses

• Autoimmune Disorders (e.g., Pemphigus or Epidermolysis Bullosa): These conditions can cause blistering of the skin and mucous membranes but are rare in children and would typically have other distinguishing features.
• Infectious Diseases (e.g., Tuberculosis or Syphilis): Certain infectious diseases can cause ulcers, but these would be unusual in this context without other specific risk factors or symptoms.
• Nutritional Deficiencies: Deficiencies like vitamin B12 or iron deficiency can cause mouth ulcers, but hand ulcers would be less common, and there would likely be other signs of malnutrition.