Prurigo Pigmentosa (Nagashima disease)

What is Prurigo Pigmentosa (Nagashima disease)?

Prurigo pigmentosa, also known as Nagashima disease or “keto rash,” is a rare skin condition first identified by Nagashima and his team in 1971. This rare skin condition typically, but not only, affects young women from East Asia. It appears as a symmetrical outbreak of itchy skin bumps on the neck, chest, and back. These bumps usually merge together into a net-like pattern, which comes and goes, resulting in darkened skin that could be concerning for aesthetic reasons.

Prurigo pigmentosa can happen due to certain metabolic changes, for instance, those that occur when one is on a ketogenic diet, which is gaining popularity recently. This text examines the suspected cause, the biological process, how doctors study the case, and how they manage this condition. It also emphasises the importance of teamwork among healthcare professionals to improve the outcomes for patients facing this rare skin condition.

What Causes Prurigo Pigmentosa (Nagashima disease)?

The cause of a skin condition called prurigo pigmentosa is still uncertain. Some theories suggest that it might be triggered by changes in your metabolism, changes in your diet, hormonal shifts, or infections.

Interestingly, there seems to be a link between prurigo pigmentosa and certain diets or lifestyle changes. For instance, it has been associated with a state called ketoacidosis, or periods of fasting, calorie reduction, and restricting carbs in your diet, like in a keto diet. There are cases where the onset of prurigo pigmentosa has coincided with high levels of ketone bodies (a type of substance produced when the body burns fat for energy) in your blood. Once the level of ketones in urine return to normal, the skin condition seems to get better, but more research is needed to fully understand this link.

Additionally, there have been cases of prurigo pigmentosa happening during pregnancy. It’s also been reported to occur after receiving a COVID-19 vaccine. Some other studies suggest that there might be an association between prurigo pigmentosa and specific immune system components known as human leukocyte antigens.

Risk Factors and Frequency for Prurigo Pigmentosa (Nagashima disease)

Prurigo pigmentosa is a skin condition that was first seen in a Japanese woman. Since then, cases have been reported all over the world, including Europe and the United States, among others. Even though it’s most often found in patients of East Asian descent, researchers believe this might be because many healthcare providers outside of East Asia aren’t familiar with the condition, leading to many cases being misdiagnosed or overlooked. This issue affects how we understand the prevalence of the disease. Prurigo pigmentosa usually affects young women in late adolescence or early adulthood.

Signs and Symptoms of Prurigo Pigmentosa (Nagashima disease)

Prurigo pigmentosa is a skin condition that is identified by itchy, red bumps, small blisters, and larger blisters in a symmetrical, net-like pattern. This usually occurs on the back, upper chest, and neck. Over time, these small red bumps develop into dark patches or plaques. Rarely, the forehead, arms, or stomach may be affected and it’s unlikely that the condition will involve the body’s moist linings, such as the inside of the mouth. The condition may reappear in the same places where it has previously occurred. Some people might exhibit one-sided, line-like, blister-like, or skin-shedding lesions, but these are infrequent cases.

• Itchy, red bumps
• Small blisters, and larger blisters arranged in a net-like shape
• Usually affects the back, upper chest, and neck
• Bumps might develop into dark patches or plaques
• Rarely affects the forehead, arms or stomach
• Seldom involves bodily linings like the mouth’s inside
• May reoccur in the previously affected areas
• Occasionally presents with one-sided, line-like, blister-like, or skin-peeling lesions

Testing for Prurigo Pigmentosa (Nagashima disease)

In order to better understand the risk of developing a skin condition called prurigo pigmentosa, doctors may sometimes recommend specific laboratory tests. These tests aren’t just for diagnosing the condition, but also for ruling out other possible underlying health issues.

There’s a range of laboratory tests that could help identify if someone is suffering from a state known as ketoacidosis, which is often found in people with this condition. These tests may include the following:

• Serum electrolytes: This is a test to check the balance of minerals like sodium, potassium, and calcium in your blood. These minerals help with various vital body functions including heart rhythm, muscle contraction, and brain function.
• Serum glucose: This test measures the amount of sugar, or glucose, in your blood. High blood glucose levels may indicate conditions like diabetes.
• Serum insulin: This test measures the level of insulin, a hormone that regulates blood sugar levels, in your blood. Too little or too much insulin could indicate a metabolic problem.
• Serum ketones, including beta-hydroxybutyrate: This test checks for the presence of substances called ketones in your blood. Your body produces ketones when it burns fat for energy, and high levels could suggest a problem with how your body is metabolizing food.
• Urinalysis: This is a type of test performed on a urine sample. It can help detect a wide range of disorders, such as urinary tract infections, kidney disease, and diabetes.
• HbA1c: Also known as the haemoglobin A1c or glycated haemoglobin test, this procedure measures your average blood sugar level for the past few months. It’s commonly used to diagnose type 1 and type 2 diabetes.

Treatment Options for Prurigo Pigmentosa (Nagashima disease)

Prurigo pigmentosa, a skin condition, often gets better on its own. However, some people might need medical treatment to help it clear up. It’s also crucial to identify and manage any underlying health conditions that might contribute to the disease.

Doctors usually treat prurigo pigmentosa with oral tetracycline or macrolide antibiotics. Minocycline is commonly used as the first line of treatment. These types of antibiotics help by reducing inflammation and controlling the body’s immune response. In some instances, a medication called dapsone might also be used. It works similarly by controlling the immune response, specifically by inhibiting the activity of certain white blood cells (neutrophils).

Alongside these oral medicines, topical treatments such as corticosteroids or calcineurin inhibitors can be applied directly to the skin. These are typically used to help alleviate itching associated with prurigo pigmentosa. However, the benefits of topical dapsone and minocycline are not extensively proven.

Colchicine, another medication that controls the immune response, has also shown potential in treating prurigo pigmentosa. Dietary modification can benefit certain people, particularly those following a ketogenic diet or coming from regions where diets inducing a state of ketosis are prevalent.

For ongoing skin color changes (hyperpigmentation) due to prurigo pigmentosa, a range of treatments are available though results can vary from person to person. These treatments include using topical agents on the skin, laser therapy, chemical peels, microdermabrasion, light treatments, and UV-B phototherapy. One study showed improvement in hyperpigmentation with a specific type of laser therapy. Hydroquinone, retinoids, and corticosteroids are the most commonly used topical treatments for such skin changes.

Other supportive measures like protecting your skin from the sun may help lessen the visible effects of prurigo pigmentosa. Be mindful that increased sun exposure can worsen existing skin pigmentation.

What else can Prurigo Pigmentosa (Nagashima disease) be?

Prurigo pigmentosa is often misdiagnosed. It can be easily confused with other skin conditions, including confluent and reticulated papillomatosis, atopic dermatitis, and contact dermatitis. Even dermatitis herpetiformis, a condition that can look similar, doesn’t usually show the same results under a biopsy. Cutaneous lupus erythematosus is another condition that might look like prurigo pigmentosa, even though it doesn’t show certain features like ballooning, spongiosis, or a certain type of inflammation in the upper layer of the skin.

However, other conditions that could be mistaken for prurigo pigmentosa include the following:

• Lichen planus pigmentosus
• Dermatitis herpetiformis
• Bullous lichen planus
• Acanthosis nigricans
• Tinea versicolor
• Terra firma-forme dermatosis
• Pityriasis lichenoides et varioliformis acuta (Mucha-Habermann disease)
• Darier disease
• Dowling-Degos disease
• Galli-Galli disease
• Primary cutaneous amyloidosis
• Erythema ab igne

What to expect with Prurigo Pigmentosa (Nagashima disease)

Prurigo pigmentosa, in most cases, has a good outcome and doesn’t lead to serious health issues. However, some people might have a lingering issue with skin discoloration, which could last for a long time and may affect their appearance. Getting treated early can help reduce the risk of this lasting discoloration.

Possible Complications When Diagnosed with Prurigo Pigmentosa (Nagashima disease)

Prurigo pigmentosa is a type of skin condition that causes inflammation. It doesn’t have any known medical complications.

Preventing Prurigo Pigmentosa (Nagashima disease)

Prurigo pigmentosa is a skin condition that patients need to be well-informed about. This includes understanding common symptoms like skin rashes, acknowledging that it’s a repeating condition, and knowing about certain factors that can make symptoms worse. The potential triggers that can worsen this skin condition include fasting and diets with restricted carbohydrates. Another important factor is controlling diabetes if you have it, as it can help prevent the return of the skin condition. It’s also crucial to know that the skin lesions that appear with this condition aren’t contagious and won’t spread to others.