Overview

Transient neonatal pustular melanosis (TNPM) is a benign condition that typically resolves itself over time and affects newborns. Infants with this condition present with pus-filled bumps known as pustules on the skin, and when these pustules rupture, brown spots are formed, known as macules. Although most macules tend to fade after two weeks, some macules become hyperpigmented and can be visible for months.¹ Neonates (newborn children) who are more commonly affected by this condition are typically dark-skinned and are African or African American.² This condition has been shown in many different studies to affect black newborns more than white newborns, as

well as those of Asian or Hispanic descent.³ Some studies have concluded that pustular skin conditions are more common in those of African descent; however, this is due to erythema toxicum neonatorum (ETN), which is another skin condition, not TNPM.⁴ It is therefore important to establish whether there is a link between ethnicity and TNPM prevalence. Although most studies suggest that those of African descent are more likely to present with TNPM, it is also necessary to understand why this is the case. This article is going to investigate the relationship between race, ethnicity and TNPM prevalence in certain populations. This investigation of TNPM prevalence in different ethnic groups will entail elucidating why there is a difference in TNPM prevalence depending on race. Future directions regarding TNPM research and clinical implications will also be explored.

Transient Neonatal Pustular Melanosis (TNPM)

TNPM has specific presentation and characteristics that make this condition distinguishable from similar diseases. There are certain lesion types that TNPM-affected individuals present with. 

Firstly, those affected have visible pustules that rupture and leave brown spots behind that are referred to as macules. These macules are not pigmented in many other conditions, thus, they are indicative of TNPM.⁵ Infants with this condition also present with collarettes, which are skin lesions which lead to skin overhanging due to keratin being loose. This occurs when pustules rupture and are present alongside macules in those with TNPM.⁶ 

As aforementioned, most TNPM instances occur either immediately or shortly after birth (within 6 months of a child being born), and this condition is typically resolved within a few weeks. This can, however, take longer depending on whether the macules undergo hyperpigmentation.⁷ TNPM is caused by a few different factors. Currently, the aetiology and pathophysiology of this condition are not well understood, and there are still questions surrounding the exact mechanism of this disease.⁸ Genetics may play a role in the presentation of pustules, as pustular psoriasis is known to be caused by six genetic variants that lead to some individuals being genetically predisposed to pustule formation.⁹ 

It is also well documented that a mutation in the IL36RN gene leads to individuals presenting with pustular psoriasis thus, there needs to be more genetic analysis to elucidate the link between genetics and TNPM presentation.¹⁰ Melanocytes are also closely linked to TNPM presentation. In congenital dermal melanocytosis, the sheath that protects the melanocytes in the skin is destroyed to an extent and as well as, melanocytes proliferate. Melanocytes are the cells within the skin that form melanin. These mechanisms are largely determined by genetic factors and have been linked to TNPM, as the macules are brown. TNPM is also linked to inflammatory factors, as polymorphonuclear neutrophils are present in the pustules. These are white blood cells that lead to inflammation. Neutrophils also lead to tissue damage through various different mechanisms.¹¹ 

Racial and ethnic variations in TNPM Prevalence

TNPM has been shown to have differing prevalence due to age and ethnicity. Many studies have demonstrated that the prevalence of TNPM is high in those of African and African American descent in comparison to other ethnic groups.¹² It has been shown that pigmentation is linked to the prevalence of skin conditions, as TNPM has a particularly high prevalence in those with dark skin who are African and African American.¹³ TNPM disproportionately affects black neonates when compared to other ethnic groups, such as Caucasians.¹⁴ 

This disease is also rare amongst people who are from Asia; however, these ethnic groups must still be aware of this condition, as it is still possible. It is important to note that some studies suggest that some Asians are likely to get this condition due to some being darker in colour however, the general consensus is that Asian, Caucasian and Hispanic individuals are less likely to present with this condition.¹⁵ 

The reason that those with African ancestry may be more susceptible to TNPM is due to melanin being linked to lesion presentation, and many lesions contain melanin, thus, individuals with higher melanin may be more susceptible to TNPM.¹⁶ It has also been suggested that genetics may play a role, as other neonatal skin conditions are due to an autosomal dominant inheritance pattern.¹⁷ Some mutations that are implicated in skin conditions, such as those in the aforementioned IL36RN gene, are more common in those from Africa. 

It has therefore been postulated that genetics has a role to play in the prevalence of TNPM amongst different ethnic groups.¹⁸ There have been conflicting results regarding this gene, but a genetic mechanism likely influences the prevalence of this condition.

Clinical implications and diagnosis

There are ways to diagnose this condition; however, this disease has fairly large implications regarding healthcare globally. It is essential to properly recognise instances of TNPM and not confuse these cases with other conditions. This is due to many skin conditions leading to pustule formation, some of which may have severe and life-threatening consequences. The onset and resolution periods are useful in confirming whether a skin condition is indeed TNPM.¹⁹ Other conditions which result in pustulosis (pustule formation) include ETN, neonatal acne and infantile acropustulosis, as well as others. Tests such as the Tzanck smear as well as gram staining, allow for these conditions to be differentiated. This is particularly useful when bacterial infections lead to similar symptoms.²⁰ It is important to reassure the parents when infants present with TNPM ass although this condition resolves itself, it can be a stressful period. This is more of an issue when the symptoms last for longer than usual, as this may be indicative of further issues or complications.²¹ 

Research gaps and future directions

In the future, those affected, as well as the families of those affected, would benefit from further research into this condition. Population studies with large sample sizes that have differing variables will allow for more information to be studied regarding this condition. For example, the effect of seasons on TNPM presentation and how the immune system is linked to TNPM prevalence.²² Studying the link between genetics and TNPM is also useful, as it is likely that genetics are responsible for the different TNPM prevalence values in each ethnic group.⁹ Studying genetics will allow more mechanisms to be elucidated. As aforementioned, more studies would allow the effect of the environment to be established, such as the weather, alongside other environmental factors.²² 

Summary

In summary, TNPM is generally more prevalent in people of African or African American descent and less prevalent in Asian, Caucasian, and Hispanic individuals. This may be due to genetic factors and certain genes leading to an increased likelihood of pustule formation. As well as this, melanin and melanocytes are linked to the presentation of TNPM, which explains the observed racial trends to an extent. It is important that healthcare providers are aware of these trends, as this will allow diagnosis to improve for infants with skin disorders. It is crucial not to confuse TNPM with other conditions such as ETN. By further researching dermatology and neonatology, this will allow more trends to be established regarding TNPM prevalence. Through increased genetic testing and more studies, it can be identified why certain trends exist and this will lead to this condition being less prevalent in the future and allow more efficient usage of healthcare resources. The parents of those affected will also be more at ease in the near future.