Transient Neonatal Pustulosis: This condition is characterized by the presence of sterile pustules or blisters on a newborn's skin, often containing eosinophils and sometimes melanin pigment. It typically resolves on its own within the first week of life, making it a likely diagnosis for a single blister with melanin pigment in a newborn.

Milia: These are small, white bumps on a newborn's skin that can sometimes appear as blisters. While they are usually white, the presence of melanin could be considered if the blister has a pigmented appearance.
Erythema Toxicum Neonatorum: A common condition in newborns, characterized by small, yellow or white bumps or blisters on a red base. The presence of melanin pigment could be a variant presentation.
Sucking Blister: Newborns may develop blisters on their skin due to sucking, which could potentially contain melanin if the blister becomes pigmented over time.

Congenital Infections (e.g., Herpes Simplex, Varicella): Although less likely, these infections can present with blisters and are critical to diagnose early due to their potential severity and need for prompt treatment.
Epidermolysis Bullosa: A group of genetic conditions that result in blistering of the skin. Early diagnosis is crucial for management and genetic counseling.

Incontinentia Pigmenti: A rare genetic disorder that can cause blisters in newborns, followed by other skin changes, including hyperpigmentation.
Congenital Melanocytic Nevus: While not typically presenting as a blister, a congenital melanocytic nevus could potentially appear as a pigmented lesion that might be mistaken for a blister.
Bullous Congenital Eruptions (e.g., Bullous Ichthyosiform Erythroderma): Rare genetic conditions that can cause blistering and skin changes, often with an onset at birth or shortly after.