Introduction

Nodular acne is a severe form of acne that causes hard nodules (small, firm lumps or knots) to develop under the surface of the skin, appearing as red bumps on the skin.¹ The nodules are large and can be very painful, lasting for weeks or months.¹ Once infected with bacteria such as Cutibacterium acnes (C. acnes), the nodules can become inflamed and aggravated.¹ Nodular acne requires specialist care and treatment from a dermatologist. Otherwise, the acne can lead to severe and permanent scarring.¹

It is important to understand the symptoms of nodular acne to provide early treatment to reduce the risk of scarring.¹ Recognising the signs of nodular acne can prompt individuals to seek medical attention as soon as possible to improve the outcome of treatment and to reduce unwanted permanent scarring that could affect one's quality of life and impact one's mental health.

Aetiology and pathophysiology

Nodular Acne can be caused by a combination of factors such as:

1. Changes to hormone levels
2. Increased production of sebum
3. Bacteria infection
4. Genetics

1. Hormonal fluctuation

Changes in the level of hormones in the body can cause nodular acne to develop.² During puberty, the body transitions from a child into an adult, which is controlled by hormones like androgen.² High levels of androgen can cause the skin to produce an excess amount of oil, leading to the clogging of pores.^1,2 

Hormones affect teenagers and young adults, especially men as they produce more androgen.¹ Individuals who are pregnant, menstruating or experiencing menopause also experience hormonal fluctuation and are at risk of developing nodular acne. 

2. Overproduction of sebum

Sebum is an oil produced by the sebaceous glands, whose main role is to prevent the skin from dehydration.³ It is made of a mixture of wax, cholesterol, fatty acids and esters of glycerol. There is an increase in sebum levels associated with individuals with acne compared to those without as sebum can block pores within the face, leading to the formation of acne.^1,3 

An excess in sebum production can be caused by dietary intake, with more sebum being produced when the diet is high in dietary fat and carbohydrates.³ Changing your diet to include more fish and seafood can lower the risk of developing acne.³ 

3. Bacterial infection

Nodular acne is a severe form of inflammatory acne caused by bacterial infection. It is caused by Cutibacterium acnes (C. acnes), which is a common bacteria found on the skin within the hair follicles and the sebaceous glands.⁴ The bacterium can become trapped inside the pores,¹ triggering an immune response that causes inflammation to occur at the affected site.⁴ This causes the nodules to form under the skin where the bacteria is trapped, alongside dead skin and sebum, causing nodular acne to form. 

4. Genetics

Genetics is an important factor that can contribute to the formation of nodular acne. You are three times more likely to develop nodular acne if there is a family history of nodular acne compared to individuals without any family history of nodular acne.⁴ Genetics is involved in which inflammatory response is triggered when the pores are blocked and responsible for the severity of acne.⁴

Clinical presentation

The clinical presentation of nodular acne includes:

1. Nodules: Firm, small lumps are found under the surface of the skin, and they can be painful. They are over 5 mm in diameter and width, and the depth can be deeper than 5 mm, depending on where the inflammation has occurred. It can even reach the subcutaneous tissues, within the dermis or on top of the skin⁵
2. Nodular acne distribution also varies depending on the gender of the individual. In males, nodular acne can be present on the skin, chest, or back, and this varies in females, where nodule acne is usually found around the chin and jawline.¹ Nodular acne can appear as a singular acne or there could be several spots that appear together¹

Symptoms of nodular acne

The symptoms of nodular acne can be separated into primary and secondary symptoms.

Primary symptoms

• Pain and tenderness around the site of nodule and sensitivity when the nodules are touched¹
• Raised lumps that are red or skin coloured
• Pain and swelling around the nodules

Secondary symptoms

• Dark spots and hyperpigmentation after inflammation
• Scarring of the nodules

Diagnosis

Differential diagnosis

Differential diagnosis is a term used to describe other conditions that have similar symptoms and clinical presentations such as nodules, small bumps under the skin, inflamed skin lesions and painful spots. Nodular acne has similar symptoms to and can sometimes be mistaken for:⁵ 

• Epidermal Cyst (sebaceous cyst) – small round bumps under the skin with a blackhead at the centre of the filled with pus that can leak 
• Lipoma – a non-cancerous lump that forms under the skin due to overgrowth of fat cells. It appears as a dome-shaped soft bump under the skin that is around 5cm wide 
• Warts – a type of skin growth caused by the human papilloma virus (HPV) which causes keratin to form on the top layer of the skin, leading to the appearance of warts
• Xanthoma – lipid deposits that appear as yellow patches or nodules on the skin 
• Basal Cell Carcinoma – the most common type of skin cancer and they appear as shiny skin-coloured bumps that are present under the skin 
• Acrochordon (Skin Tags) – occurs when the body produces extra cells on the skin's top layer, causing bumps to form which are painful and itchy due to friction against clothes 

Diagnostic criteria

To diagnose nodular acne, a clinical examination will need to be carried out by a dermatologist who will examine the skin and ask questions about the symptoms and family history of acne.¹ As mentioned above, an individual is more likely to develop nodular acne if severe acne is present in the immediate family. The examination is mostly visual, focusing on the appearance of nodules and symptoms, and there is no laboratory testing required for diagnosis.

The dermatologist may ask questions such as:¹

1. How painful are the spots?
2. When did they appear and the location of the nodules?
3. Does anyone in your family have a history of severe acne?
4. Did you have any previous acne treatment? If so, how effective were they?
5. Do you take any medication?

Impact on quality of life

Nodular acne can significantly impact an affected individual’s quality of life and self-esteem. Due to the potential for severe and permanent scarring, individuals may struggle with body image, affecting mental health, which can contribute to anxiety and depression. Alongside physical scarring, nodular acne is a painful type of acne, and chronic pain can interfere with daily activities, further reducing overall quality of life. 

Summary

Nodular acne is a severe form of acne that causes hard nodules to form under the surface of the skin, appearing as red bumps on the skin.¹ The nodules are large and can be very painful, lasting for weeks or months and can lead to severe and permanent scarring.¹ It is caused by a combination of changes in hormones (especially androgen), an increased level of sebum, bacterial infection and genetics. These all contribute to inflammation within the hair follicles and pores beneath the skin, leading to the formation of nodules in the affected area and causing painful red bumps under the skin. 

Nodular acne is often characterised by a raised red lump that is painful and tender when touched. Permanent scarring is also another symptom of nodular acne, which could have a lasting impact on an affected individual, interfering with their quality of life. 

Nodular acne can significantly impact an individual’s mental health and well-being as the permanent scarring can affect their self-esteem and lead to body image issues. Hence, it is important to understand and recognise the symptoms of nodular acne to provide the best treatment as fast as possible. Seeking dermatologist-directed care can help manage and treat nodular acne effectively to reduce scarring and prevent future complications, ultimately improving quality of life.