What are the other Names for this Condition? (Also known as/Synonyms)

• Keto Rash
• Nagashima Disease
• PP (Prurigo Pigmentosa)

What is Prurigo Pigmentosa? (Definition/Background Information)

• Prurigo Pigmentosa (PP) is an uncommon condition that is characterized by inflammatory red skin rashes with reticulated (mesh-like) pattern of darkly pigmented areas. The condition is more common in young Asian women
• Prurigo Pigmentosa is associated with a metabolic state called ketosis, which develops when there is an abnormally increased level of ketones in the body tissues, which occurs from disorders, such as poorly-controlled diabetes, or from strictly adhering to a low-carbohydrate “weight loss” diet called ketogenic diet
• No significant complications of Prurigo Pigmentosa are generally observed. The condition is known to resolve by undertaking suitable treatment of the underlying cause. The skin rashes improve and the hyperpigmented (dark) skin patches are known to fade away over time

Who gets Prurigo Pigmentosa? (Age and Sex Distribution)

• Prurigo Pigmentosa may be observed in individuals of a wide age group. However, many cases are reported in teenagers and young adults
• Both males and females are affected; more women than men are affected in a 2:1 ratio
• Worldwide, there is no racial or ethnic preference observed. But a higher incidence of the condition is reported among Asians

What are the Risk Factors for Prurigo Pigmentosa? (Predisposing Factors)

The risk factors for Prurigo Pigmentosa may include:

• Anorexia nervosa
• Atopy - genetic susceptibility to allergies
• Fasting for a long period
• Ketogenic diets
• Post-bariatric surgery
• Pregnancy
• Sjogren syndrome
• Uncontrolled diabetes

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Prurigo Pigmentosa? (Etiology)

Prurigo Pigmentosa is associated with the metabolic condition ketosis, which may arise from factors such as a strict keto diet, diabetes, eating disorders, and fasting.

• However, the exact cause-effect relationship between ketosis and Prurigo Pigmentosa is not well understood
• Experts have also proposed explanations associating Prurigo Pigmentosa with several forms of allergic and irritant contact dermatitis, although these remain currently inconclusive

What are the Signs and Symptoms of Prurigo Pigmentosa?

The signs and symptoms of Prurigo Pigmentosa may vary from one individual to another and may be mild or severe. It may include:

• Presence or itchy red rashes that appear as raised spots (papules)
• These inflamed red spots coalesce/merge to form a reticulate (mesh-like) pattern
• The reticulate pattern is often symmetrical in appearance
• Once, the inflammation resolves, dark pigmented patches outlining the reticulated pattern is noted
• Most of the rashes form on the chest, upper back, abdomen, and base of the spine. Occasionally, they may be present on the arms, legs, or face
• The hair, nails, and mucosal surfaces, such as the oral cavity and anogenital regions, are not generally affected

How is Prurigo Pigmentosa Diagnosed?

A diagnosis of Prurigo Pigmentosa may involve the following exams and procedures:

• Physical examination of the individual and medical history evaluation is important
• Dermoscopy: Dermoscopy is a diagnostic tool where a dermatologist examines the skin using a special magnified lens
• Wood’s lamp examination: In this procedure, the healthcare provider examines the skin using ultraviolet light. It is performed to examine the change in skin pigmentation
• Skin biopsy: A skin tissue biopsy is performed and sent to a laboratory for a pathological examination. The pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Prurigo Pigmentosa?

The possible complications due to Prurigo Pigmentosa include:

• Emotional stress due to cosmetic issues
• Recurrence of the condition following treatment
• Treatment complications

How is Prurigo Pigmentosa Treated?

The treatment measures available for Prurigo Pigmentosa include:

• Treating the underlying causative condition
• Consuming adequate amounts of carbohydrate if the individual was earlier on a keto diet
• Symptomatic treatment may be considered for the skin lesions using doxycycline or erythromycin antibiotics, which are known to be beneficial
• The hyperpigmented (dark) patches are known to slowly fade and resolve over time
• Topical or oral corticosteroids are known to be ineffective in treating Prurigo Pigmentosa

Regular follow up visits with the healthcare provider is important and recommended.

How can Prurigo Pigmentosa be Prevented?

Prurigo Pigmentosa may be prevented by considering the following steps:

• Avoid prolonged fasting
• Check with a dietitian or healthcare provider before following a ketogenic diet
• Undertake suitable treatments for any underlying condition that may predispose one to Prurigo Pigmentosa
• Keep diabetes under control through suitable lifestyle changes such as proper diet and physical exercise

What is the Prognosis of Prurigo Pigmentosa? (Outcomes/Resolutions)

The prognosis of Prurigo Pigmentosa is generally good with adequate treatment of the underlying condition. The rashes and pigmented patches are known to resolve with suitable treatment.

Additional and Relevant Useful Information for Prurigo Pigmentosa:

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/healthy-living/skin-disorders/