CARP Skin Condition All you need to know

Confluent and Reticulated Papillomatosis CARP Skin Condition or CRP , is an asymptomatic skin condition that is associated with hyperpigmented papules and plaques around the neck, armpits, and trunk.

It is also called Gougerot-Carteaud syndrome, as it was first described by two French dermatologists named Gougerot and Carteaud, in 1927.

CARP is one of the diseases that are caused by abnormal keratinization of the skin. Others include tinea versicolor, Acanthosis Nigricans, Darier disease, and some genetic disorders.

However, a unique characteristic of CARP is the peripheral, net-like configuration of the plaques, and their distinct location in the trunk, axilla, and neck.

CARP Skin condition symptoms

The following are clinical symptoms of CARP that are should be present before diagnosing this disease;

  • Skin lesions above the trunk

Papules of CARP come together in plaques or patches. The arrangement of the papules in the plaques is; confluent in the center and reticulated towards the periphery.

  • Hyperkeratosis

Hyperkeratosis is an unusual thickness in the outermost layer of the skin, which is the stratum corneum.

  • Papillomatosis

This is a protrusion of papillae from the second layer of the skin, onto the surface of the skin. It makes the skin look rough.

  • Hyperpigmentation

The patches in CARP are dark or brown colored. This is due to

Causes of CARP on the skin

CARP on the skin is generally caused by dysregulation of skin cell turnover. However, to find the specific cause one would need to find the cause of the dysregulation in the first place.

Although it has not been made clear, researchers have made several hypotheses that might be the causes of this condition. These hypotheses are;

●    Dietza Infection

During a 2005 research about the cause of CARP, a new actinomycete was obtained from CARP on a patient’s skin. This implied that the skin condition is caused by a bacterial infection.

The bacteria, in this case, is a gram-positive aerobe that is both non-acid and non-alcohol fast. With these characteristics, this bacteria was believed to be the primary cause of the dysregulation of skin cell turnover.

●    Hormonal Imbalance

Some patients of CARP have a past or present history of insulin resistance which was caused either by obesity or diabetes. To confirm this, researchers noticed that when these patients lost weight and maintained healthy blood glucose levels, CARP was relieved accordingly.

The theory is that high insulin levels increase the chances of binding several growth factors including insulin growth-factor 1 fibroblast growth factor. This binding leads to the proliferation of epidermal cells with low rates of apoptosis.

However, not all patients of CARP skin condition are obese or with diabetes, which makes this theory restricted for some people.

●    Genetics

While some cases might be individual problems, others could be generational problems. There are two known ways whereby skin functioning can be manipulated by genetics.

In the first scenario, CARP skin condition could be caused by the activation of K16, a gene that is linked to keratin disorders like palmoplantar keratoderma. In other scenarios, the patient has four copies of the 15q chromosome which is a genetic defect that has a role in the dyspigmentation of the skin.

●    External agents

Researchers also propose that CARP skin condition could also be caused by external agents like Ultra Violet rays from the sun. The hypothesis is that UV rays can stimulate one temporary action in the skin, like temporary epidermal hyperplasia that is accompanied by melanin synthesis.

This, however, has not been proven experimentally and as such, is still a hypothesis.

CARP Skin condition vs Acanthosis Nigricans

CARP and Acanthosis Nigricans (AN) are very similar skin conditions that are most times mistaken for each other. The major differences between CARP and AN are the places they are found and their epidermal histology.

Lesions from CARP skin condition are mostly located on the trunk amongst other places. In comparison, lesions of AN are mostly seen in the axilla than in other places. Also, AN is mostly seen in obese people compared to CARP.

The histological changes of the epidermis in AN are more intense compared to CARP. The former shows great degrees of melanocytic pigmentation and pigmentation while the latter shows little or mild changes.

CARP Skin condition vs Tinea Versicolor

This is another similar skin condition to CARP but their differences are in a wide range of things. Unlike CARP which is associated with hyperpigmented lesions, Tinea versicolor comes with hypopigmented lesions that are mostly noticed during summer.

Also, lesions of tinea versicolor do not have a rough surface like those of CARP skin condition. Instead, they are collections of scaly macules and patches that might feel flaky or scaly.

Also, TN is a fungal infection and can be cured by applying topical antifungal creams, unlike CARP skin condtion which has several hypothetical causes and is not cured with just antifungal creams.

CARP Skin condition vs Darier disease

Darier disease is a genetic skin condition that is characterized by greasy and wart-like lesions, unlike CARP skin condition which has hyperpigmented lesions.

The physical difference between both conditions is that lesions of Darier disease do not have the reticulated pattern as those of CARP. They have an overlying greasy scale instead.

Also, darier disease is mostly caused by family history. Unlike CARP, the darier disease can be cured with oral retinoids within 3 months.

How to treat CARP skin condition

The most recent treatment for CARP skin condition is taking 50mg to 100mg of oral minocycline twice a day for 6 weeks. There is no clear understanding of how minocycline works but it is believed that its anti-inflammatory properties help in treating this skin condition.

For some people, the duration of treatment might be longer than 6 weeks, it might extend to 2 or 5 months. This depends on how long it took before a diagnosis was given. If the diagnosis was given early enough, the condition would be treated faster than if the opposite was the case.

Alongside minocycline, topical retinoids are also applied to the patches to aid the treatment. These topical ointments are strictly for external use.

The treatment methods mentioned above give the most consistent results. Other medications that could be used include;

  • The use of Keratolytics
  • Vitamin A (either intramuscular or topical forms)
  • Sodium thiosulphate
  • Ammoniated mercury
  • Thyroid extract
  • Antimycotics
  • Calcipotriene

Although some of these medications might show positive results, it is imperative to consult your doctor before taking any medication. It is also important that you only take medications that are prescribed by your doctor to prevent other complications.


Confluent and Reticulated Papillomatosis is a skin condition that can be gotten by direct and indirect contact with a carrier. Although the condition is quite popular, it is often misdiagnosed with similar conditions like Acanthosis Nigricans, Tinea Versicolor, and Darier disease.

The differences between these conditions are discussed in this article including their different treatment methods. As the causes of CARP skin condition vary, it might be difficult to get a quick diagnosis.

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