Oral Thrush (Candidiasis): This is a common condition in infants, characterized by white patches on the tongue and mucous membranes. The absence of redness or feeding difficulties supports this diagnosis, as oral thrush typically doesn't cause significant inflammation or discomfort in infants.

Milk Tongue (Lingual Lipase-Related Lesions): These are benign white bumps that can appear on an infant's tongue due to the enzymatic activity of lipase in milk. They are harmless and resolve on their own.
Fordyce Spots: These are small, white or yellowish bumps on the lips, tongue, or inside of the cheeks. They are caused by the abnormal presence of sebaceous glands in the mucous membranes and are generally harmless.

Herpes Simplex Virus (HSV) Infection: Although less likely given the absence of redness or systemic symptoms, HSV can cause oral lesions. It's crucial to consider this diagnosis due to its potential severity and the need for antiviral treatment.
Congenital Syphilis: This condition can cause a variety of oral manifestations, including mucous patches or snail track ulcers, though these are less common. Given the potential severity of untreated syphilis, it's essential to rule out this diagnosis.

Darier's Disease: A rare genetic disorder that can cause white or yellowish papules on the mucous membranes, among other symptoms. It's an unlikely diagnosis in a 7-week-old infant presenting with isolated oral findings.
White Sponge Nevus: A rare, benign condition affecting the mucous membranes, characterized by white, spongy lesions. It is usually present from birth or appears in early childhood.