Neonatal Pustular Melanosis

Transient neonatal pustular melanosis is a benign, self-limited condition of unknown etiology.[1, 2, 3, 4] Historically, the disorder was lumped together with vesicular and bullous lesions and called pemphigus neonatorum. It was not described as a separate entity until 1976, although it may have been recognized as early as 1961 and published under the name of lentiginosis neonatorum. Note the image below.

Ruptured pustules and vesicles with remaining characteristic collarette of scale and brown hyperpigmented macules. Courtesy of Anthony J. Mancini, MD.

The etiology is unknown. Some reports have described cases that evolved into erythema toxicum neonatorum[5] ; however, in the author’s opinion, the disorders may coexist and are clinically distinct entities.

US frequency

Few reports of large numbers of screened infants are available; however, incidence has been reported to be as much as 2.2% in white infants and 4.4% in black infants.

Race

Transient neonatal pustular melanosis is common in black infants. It can be observed in all racial groups, especially those with darker constitutive pigmentation, Latinos, South Asians, and those of Mediterranean extraction.

Age

The eruption is almost always present at birth but the clinical appearance or stage may vary.

Neonatal pustular melanosis is a completely benign condition that is not known to cause any long-term sequelae.[6] The prognosis is excellent. Postinflammatory pigmented macules resolve in 2-4 months.

If pustules continue to erupt, other diagnoses should be considered.

Term or near-term infants are born with this condition. Pustules are usually uniformly sized and wipe off easily in the delivery suite.

The primary lesions in neonatal pustular melanosis progress through three stages of development. Initially, they appear as rather uniform round 2- to 4-mm nonerythematous pustules. They are not clear vesicles; rather, they contain milky, purulent exudate. The pustules rupture easily. They are frequently missed because they are superficial and are usually wiped off easily in the delivery suite when the newborn is cleansed of vernix. Pustules on the thicker areas of skin such as the knees or palms may persist for several days.[7, 8]

Next, a delicate collarette of thin white scale is left around the perimeter of each denuded pustule. Near-term infants, especially those delivered by cesarean delivery, may exhibit just the unbroken pustules, and term infants may have only macules remaining, usually with the telltale collarette of flaking epidermis.

Lastly, within hours of exposure to the terrestrial environment, the central pigmented brown macule becomes apparent. The macules are round, have smooth and distinct borders, and are frequently confused for freckles. They may be profuse or sparse and typically are found under the chin and on the neck, upper chest, back, and buttocks. Occasionally, the palms, soles, and scalp are affected.

When considering suspected neonatal pustular melanosis, the following should also be considered:

• Erythema toxicum neonatorum: These lesions are small papules on an erythematous base, contain predominantly eosinophils, and do not heal with postinflammatory hyperpigmentation.

• Congenital cutaneous candidiasis: The pustules are usually very inflamed and contain organisms on laboratory smear or biopsy.

• Impetigo: Pustules are inflamed and contain organisms on laboratory smear and culture.

• Congenital Langerhans cell histiocytosis: Widely distributed papules and pustules form adherent crusts, not frecklelike macules.

• Congenital varicella: Pustules are larger, numerous, generalized, and widely dispersed in the setting of an ill neonate with unstable vital signs.

• Miliaria: This characterized by clear vesicles (crystallina) or pustules (pustulosa) that erupt in a setting of hyperthermia.

• Herpes simplex: Lesions begin as vesicles, become turbid, and develop into pustules. The vesicles are grouped or clustered and contain multinucleated giant cells.

• Milia: This is characterized by firm, white, superficial, pin-head–sized papulelike cysts filled with keratin debris.

• Acropustulosis: The pustules predominate on the palms and soles and are not present at birth.

If the appearance is typical of transient neonatal pustular melanosis, no further workup is indicated. If appearance is not typical, potassium hydroxide preparation, Gram stain, and Wright-Giemsa stain can support other diagnoses in the differential. In atypical cases, pustules can be cultured for bacteria and clustering of pustules should prompt polymerase chain reaction to identify possible herpes simplex.

Wright-Giemsa stain of pustule contents demonstrates a predominance of neutrophils. Few, if any eosinophils are present. The brown macules are not true freckles or lentigines. Skin biopsy shows pigment incontinence characteristic of postinflammatory hyperpigmentation. The diagnosis of Langherhans cell histiocytosis can only be made by skin biopsy.

No treatment is indicated. Reassure parents that neonatal pustular melanosis is a benign finding and that it disappears.

Drug therapy currently is not a component of the standard of care for this condition.