Differential Diagnosis for the Presented Rash

The following differential diagnoses are considered for the 1-year and 8-month male patient presenting with a rash characterized by multiple small pinpoint spots of different sizes, a few millimeters in diameter, located on the chest, back, and cheeks, accompanied by itchiness but no erythema.

• Single Most Likely Diagnosis
  • Insect Bites: Given the description of the rash as itchy, pinpoint spots without erythema, and the lack of response to hydrocortisone and fucidin, insect bites are a plausible explanation. The distribution on exposed areas like the chest, back, and cheeks supports this diagnosis.
• Other Likely Diagnoses
  • Papular Urticaria: This condition is caused by an allergic reaction to insect bites and can present with itchy papules. It's a common condition in children and could explain the symptoms.
  • Folliculitis: Although the patient has been treated with fucidin (an antibiotic), folliculitis (inflammation of the hair follicles) could still be considered, especially if the rash is centered around hair follicles. However, the lack of response to antibiotics might suggest otherwise.
  • Pityriasis Rosea: This condition can start with a herald patch followed by a secondary eruption of smaller patches, typically on the trunk. However, the absence of a described herald patch and the pinpoint nature of the spots make this less likely.
• Do Not Miss Diagnoses
  • Scabies: Although scabies typically presents with severe itching and burrows, it's crucial not to miss this diagnosis due to its contagious nature and the potential for severe discomfort. The distribution and the fact that it's itchy raise scabies as a possibility, despite the lack of described burrows.
  • Meningococcemia: This is a life-threatening condition that can present with a petechial or purpuric rash. Although the description doesn't perfectly match, any rash in a child that could potentially be related to a serious infection like meningococcemia must be considered.
• Rare Diagnoses
  • Erythema Multiforme: This condition can present with target lesions and is often associated with infections or medications. The description provided doesn't perfectly align with erythema multiforme, but it's a consideration in the differential diagnosis of rashes.
  • Kawasaki Disease: Characterized by fever, rash, mucous membrane changes, and lymphadenopathy, Kawasaki disease is a rare but important diagnosis to consider in children with rash and systemic symptoms. However, the provided description lacks key features of Kawasaki disease.

Given the information, a fungal infection is less likely based on the description provided, but it cannot be entirely ruled out without further examination or diagnostic tests. The patient's lack of response to hydrocortisone and fucidin suggests that further diagnostic workup or consultation with a dermatologist may be necessary to establish a definitive diagnosis.