Differential Diagnosis for Mild Redness of Tip of Penis in a 7-Month-Old

Single Most Likely Diagnosis

• Irritant Dermatitis: This is likely due to the exposure of the penis to irritants such as urine, feces, or soap, leading to mild inflammation and redness. The age of the child and the absence of other symptoms support this diagnosis.

Other Likely Diagnoses

• Eczema (Atopic Dermatitis): Although less common in this specific location, eczema can cause redness and inflammation. A family history of atopic diseases might increase the likelihood.
• Contact Dermatitis: Similar to irritant dermatitis but caused by an allergic reaction to substances like certain soaps, diapers, or creams.
• Balanitis: An inflammation of the glans penis, which can be caused by poor hygiene, infection, or an allergic reaction. It's more common in uncircumcised males due to the potential for smegma accumulation.

Do Not Miss Diagnoses

• Urinary Tract Infection (UTI): Although the child is asymptomatic aside from the redness, UTIs can present subtly in infants and are crucial to diagnose early to prevent long-term kidney damage.
• Sexually Transmitted Infections (STIs): While highly unlikely in a 7-month-old, considering non-accidental injury is essential in any case of genital symptoms in infants.
• Circumcision Complications: If the child is recently circumcised, complications such as infection or meatal stenosis could present with redness.

Rare Diagnoses

• Psoriasis: Although rare in infants, psoriasis can cause red, scaly patches on the skin, including the genital area.
• Lichen Sclerosus: A rare condition that can cause thinning and patchy skin changes, often in the genital area, and can be seen in children.
• Zinc Deficiency: Can lead to skin lesions and might cause redness in the genital area among other symptoms.

Each of these diagnoses should be considered with the child's full medical history, physical examination, and potentially further diagnostic tests to determine the cause of the redness.