Transient neonatal pustular melanosis (TNPM) is a harmless skin condition affecting newborns. Bumps are visible on the skin of TNPM infants, which are known as pustules that are quite significantly noticeable at birth. These bumps are usually pus-filled and can potentially rupture, causing white-encircled dark spots on the skin that fade over time. TNPM is benign (not cancerous) in nature, and the bumps do not itch or scar. The condition has the potential to subside without treatment.

Clinical features

The key clinical feature of this condition is the presence of pustules, which occur on an unaffected base, which is non-erythematous.¹

• The commonly affected body areas include the forehead, posterior ears, neck, chin, back, upper chest, thighs, buttocks, abdomen, palms, and soles
• The pustules have been present since birth and evolve without the development of new lesions
• Lesions can either have a single or clustered occurrence
• The pigmented macules can demonstrate a collarette of scales
• The pustules may leave behind an area of hyperpigmentation that fades within months
• There are no systemic symptoms, meaning symptoms affecting the entire body, associated with the condition, or laboratory abnormalities

Commonly affected locations

The lesions of TNPM begin as 2-3 mm vesiculo-pustules (blisters) that are without a surrounding erythema (redness). These blisters are prone to rupture easily, leaving behind pigmented macules (spots). Blisters have a resolution time of 48 hours; however, the remaining dark spots will take weeks to months to fade. Lesions may occur as solitary or clustered. TNPM may occur on any part of the newborn's body, with the typical locations being the forehead, chin, behind the ears, neck, and back. Palms and soles may even be affected in rare cases. The cause of the disease is not clear yet. With respect to ethnicity, TNPM is more prevalent in black infants as compared to white infants, with higher prevalence in infants delivered at term than those delivered pre-term. There is no disparity between genders. TNPM can be diagnosed by clinical examination and does not require any special testing. However, if vesicular fluid is examined under a microscope, numerous neutrophils (a type of white blood cell) can be observed.TNPM is self-limiting and resolves without consequence; therefore, no treatment is necessary. 

Rare or unusual locations

An unusual case has been discussed by Michelle Marie Boffa and colleagues, which reported predominance of vesiculobullous, with a notable absence of simple pustules. Additionally, there was a presentation of patches of desquamation over the back, with a large patch over the buttocks, and some annular desquamated lesions over the scalp.²

Diagnosis

Although the diagnosis is based on clinical presentation, in cases of diagnostic uncertainty, screening for other pathologies requiring urgent medical attention is suggested. Investigations can include a blood film, peripheral blood count, and culture, accompanied by pustular fluid gram staining, viral PCR (polymerase chain reaction) tests, microscopy and blood culture. In TNPM, these investigations should all be normal and not yield any organisms after 48 hours. Abundant polynuclear neutrophils and occasional eosinophils can be observed in a cytological examination of pustular fluid.  A skin biopsy isn’t usually necessary; however, if performed, this would demonstrate subcorneal or intraepidermal pustules or vesicles.²

Summary

• Transient neonatal pustular melanosis (TNPM) is a harmless skin condition affecting newborns. Infants with TNPM demonstrate bumps on the skin known as pustules that are quite significantly noticeable at birth
• The lesions of TNPM are present since birth, beginning as 2-3 mm vesiculo-pustules (blisters) that do not have a surrounding erythema (redness)
• Rare or unusual locations include presentation of patches of desquamation over the back, with a large patch over the buttocks, and some annular desquamated lesions over the scalp

FAQs

Where do TNPM lesions appear most commonly?

They typically have an occurrence on the face, trunk, and extremities

Can TNPM lesions have an appearance on the palms and soles?

Yes, TNPM may also involve the palms and soles, unlike many other neonatal rashes

Are mucous membranes affected in TNPM?

No, mucous membranes are not affected in this disease

Are the lesions widespread or localised?

The lesions in this disease are often generalised, with pustules that are scattered and accompanied by hyperpigmented macules, but have the most frequent occurrence on the face, back, chest, and limbs

Do lesions favour flexural or pressure areas?

No, TNPM does not demonstrate a preference for such areas

Which areas are most frequently affected by TNPM lesions?

The face, trunk, and extremities are the most common sites

Can TNPM lesions appear on the palms and soles?

Yes. TNPM is a neonatal pustular eruption that involves palms and soles, which helps distinguish it from other similar rashes

Which areas are usually spared?

Mucous membranes and, in most cases, the scalp are typically spared

Do lesions look different depending on the site (face vs trunk vs limbs)?

No. The characteristic appearance with the same sequence of events is the same across all locations

Do lesions cluster in specific regions?

Lesions are often scattered, instead of being clustered, though multiple pustules may occur in close proximity on the trunk and extremities

How can distribution assist in differential diagnosis?

• TNPM: Involves face, trunk, limbs, palms, soles; mucosa spared
• Congenital infections (e.g., HSV, Candida): May involve mucosa, clustered vesicles, systemic signs
• Erythema toxicum neonatorum (ETN): Spares palms and soles

Do TNPM lesions recur at the same site?

No, following the healing of a pustule, it leaves a hyperpigmented macule that resolves spontaneously over weeks to months without recurrence at that spot