What do the letters in the acronym PUVA stand for?

The acronym PUVA represents the two main components used in this therapy: psoralen, a drug that sensitizes the skin, and UVA, which refers to ultraviolet A light.

How does psoralen function within PUVA therapy to aid in treating skin conditions?

Psoralens act as photosensitizing agents, significantly increasing the skin's sensitivity to ultraviolet A (UVA) light. This heightened sensitivity allows UVA radiation to be effective at lower doses, making it a potent treatment for conditions like psoriasis and vitiligo.

How does PUVA therapy relate to the broader category of photodynamic therapy?

While photodynamic therapy involves using light-sensitive compounds that become toxic upon light exposure to target diseased cells, PUVA therapy is often considered a distinct technique. Photodynamic therapy is a general method using nontoxic compounds that become toxic to specific cells when activated by light.

What are psoralens, and how are they obtained or administered for PUVA therapy?

Psoralens are naturally occurring or synthetically manufactured compounds that make the skin more sensitive to UV light. For PUVA therapy, they can be administered systemically by taking them as pills or applied topically, such as by soaking the skin in a psoralen solution.

Explain the mechanism by which PUVA therapy helps in treating vitiligo.

In the context of vitiligo, PUVA therapy enhances the sensitivity of melanocytes, the cells responsible for producing skin pigment, to UVA light. Melanocytes possess sensors that detect UV light, initiating the production of melanin, which provides skin color and protection.

What advantages do LED PUVA lamps offer over traditional fluorescent lamps in treatment?

LED PUVA lamps provide more intense light compared to fluorescent lamps. This allows for shorter treatment times, increases the therapy's effectiveness, and enables the use of a weaker concentration of psoralen.

How is the initial UV dosage determined for a patient undergoing PUVA therapy?

Physicians and physiotherapists typically select a starting UV dose based on the patient's individual skin type. This dose is then gradually increased during subsequent treatment sessions until the skin shows a response, commonly indicated by a slight pink coloration.

What is the purpose of testing a patient's skin before initiating PUVA treatments?

Testing a small area of the patient's skin after they have ingested psoralen helps determine the minimum phototoxic dose (MPD) or minimal erythema dose (MED). This allows clinicians to establish a precise starting dose for treatment, potentially optimizing effectiveness and reducing the number of sessions needed.

What is the minimum phototoxic dose (MPD) or minimal erythema dose (MED) in the context of PUVA therapy?

The minimum phototoxic dose (MPD) or minimal erythema dose (MED) is defined as the dose of UVA light that causes redness in the skin approximately 12 hours after a patient has taken psoralen. This measurement serves as a baseline for initiating PUVA treatment.

How does narrowband UVB therapy compare to PUVA therapy, particularly regarding patient convenience and drug use?

Narrowband UVB therapy is often preferred over PUVA for conditions like vitiligo because it does not require the use of psoralen and is generally easier to administer, especially over larger skin areas. Treatment frequency is similar, typically twice weekly in a clinic or daily at home.

Why might PUVA therapy be more effective than narrowband UVB therapy on the legs and hands?

PUVA therapy may be more effective on the legs and hands because UVA light penetrates deeper into the skin than UVB light. The melanocytes in the skin of the hands and legs are located deeper, and UVA's greater penetration can reach them more effectively, whereas narrowband UVB is largely blocked by the skin's uppermost layer.

What is melanin, and what is its function in the skin concerning UV exposure?

Melanin is a dark pigment produced by cells called melanocytes. Its primary function is to absorb UV light, acting as a natural protective shield for the body's cells located beneath the skin's surface.

How do melanocytes respond to UV light, and what is the outcome of this response?

Melanocytes have specific receptors that detect UV light. Upon detecting UV radiation, these cells are triggered to produce melanin, the pigment responsible for skin color. This process is a protective mechanism against UV damage.

What method exists for treating small, localized patches of vitiligo with psoralen to minimize side effects?

For small spots of vitiligo, psoralen can be applied directly onto the affected areas as drops. This localized application uses a very small amount of the drug, significantly reducing the risk of systemic side effects.

What are the common side effects reported by patients taking oral psoralen for PUVA therapy?

When psoralen is taken orally, particularly in doses around 10 mg, some patients may experience adverse effects such as nausea and itching.

What alternative PUVA treatment is suggested for patients experiencing side effects from oral psoralen?

PUVA bath therapy is recommended as a potential alternative for patients who suffer from side effects like nausea or itching after ingesting oral psoralen.

What is the primary long-term health concern associated with the prolonged use of oral PUVA therapy?

The long-term use of oral PUVA therapy has been associated with an increased risk of developing skin cancer.

Which specific type of skin cancer is identified as a significant complication of PUVA therapy for psoriasis?

Squamous cell skin cancer is noted as the most significant complication that can arise from PUVA therapy when it is used to treat psoriasis.

What two factors inherent to PUVA therapy contribute to genome instability and cancer risk?

The two carcinogenic components of PUVA therapy that negatively impact genome stability are the UVA light radiation itself and the psoralen's ability to intercalate, meaning insert itself, into the DNA structure.

What ancient Egyptian practice involved using plant juice and sunlight to treat vitiligo?

Around 2000 BC, ancient Egyptians treated vitiligo by applying the juice of the *Ammi majus* plant to the skin and then encouraging patients to expose the treated areas to sunlight.

What plant, historically used in the Nile Valley for vitiligo, contains compounds relevant to PUVA therapy?

The plant referred to as "aatrillal" in the Nile Valley during the 13th century, which was used to treat vitiligo, has been identified as *Ammi majus*. This plant contains significant amounts of psoralen derivatives.

Which specific psoralen derivatives found in *Ammi majus* are known for their photosensitizing effects?

The plant *Ammi majus* contains substantial quantities of bergapten and methoxsalen, both of which are psoralen derivatives recognized for their ability to increase skin sensitivity to light.

Who developed an early phototherapy machine for skin diseases using UV light, and in what era?

Niels Ryberg Finsen, working in Copenhagen, developed a substantial phototherapy machine in the 1890s designed to treat various skin diseases through the application of UV light.

What contribution did Gustave Trouvré make to phototherapy technology in 1900?

In 1900, French electrical engineer Gustave Trouvré created a miniaturized version of Finsen's phototherapy machine. His innovation involved a series of portable light radiators intended for healing skin conditions like lupus and epithelioma.

When did phototherapy machines utilizing chemically synthesized components become available?

Machines employing chemically synthesized forms of phototherapy have been accessible since the 1970s.

Who pioneered the modern development of PUVA therapy by using crystalline methoxsalen and sunlight?

Abdel Monem El Mofty, affiliated with Cairo University Medical School, initiated the development of modern PUVA therapy in the 1940s. He used crystalline methoxsalen (8-methoxypsoralen, also known as xanthotoxin) followed by exposure to sunlight to treat vitiligo.

What is the Medical Subject Headings (MeSH) code assigned to PUVA therapy?

The MeSH code for PUVA therapy is D011701.

What related dermatological treatments or conditions are mentioned in the 'See also' section of the article?

The 'See also' section lists Goeckerman therapy and PUVA lentigines, indicating related therapeutic approaches or conditions associated with PUVA treatment.

What is the fundamental principle of photodynamic therapy (PDT)?

Photodynamic therapy is based on the principle of using compounds that are initially non-toxic but become toxic when exposed to specific wavelengths of light. This light-activated toxicity is then used to selectively destroy targeted diseased cells, often malignant ones.

How does the depth of light penetration differ between UVA and UVB, and why is this significant for PUVA therapy?

UVA light penetrates deeper into the skin than UVB light. This difference is important because melanocytes, the pigment-producing cells, are located deeper in the skin, particularly on the hands and legs. UVA's deeper penetration makes PUVA potentially more effective for these areas compared to UVB, which is largely absorbed by the superficial skin layers.

What is the significance of melanin in protecting the skin from UV radiation?

Melanin is a pigment that absorbs UV light. By absorbing these harmful rays, melanin acts as a protective barrier, preventing the UV radiation from damaging the cells deeper within the skin.

Puva Therapy Wiki: Illuminating Skin Health: The Science of PUVA Therapy

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Overview

Photochemotherapy Defined

PUVA therapy is a specialized form of ultraviolet light treatment employed for various dermatological conditions. It combines the administration of a photosensitizing agent, psoralen, with exposure to ultraviolet A (UVA) light.^[1]^[2]^[3] This synergistic approach is particularly effective for conditions such as vitiligo, eczema, psoriasis, graft-versus-host disease, mycosis fungoides, large plaque parapsoriasis, and cutaneous T-cell lymphoma.

Mechanism of Action

Psoralens, whether ingested orally or applied topically, render the skin significantly more sensitive to UVA radiation. This heightened sensitivity allows UVA energy to exert its therapeutic effects at lower, safer doses. The interaction between psoralen and UVA light is crucial for its efficacy in treating conditions like psoriasis and vitiligo. In vitiligo, it stimulates melanocytes, the pigment-producing cells, to increase melanin synthesis in response to UVA exposure, thereby restoring skin color.

Distinction from Photodynamic Therapy

While PUVA therapy utilizes light-sensitive compounds and light exposure, it is often distinguished from photodynamic therapy (PDT). PDT is a broader category involving light-activated compounds that become toxic to targeted diseased cells. PUVA's specific mechanism, involving psoralen's interaction with DNA and its photosensitizing properties, sets it apart, although both are forms of light-based treatments.^[4]^[5]

Procedure

Psoralen Administration

Psoralens, available in both natural and synthetic forms, are administered to sensitize the skin. This can be achieved systemically via oral medication (pills) or topically by direct application, such as soaking the affected skin in a psoralen-containing solution. The choice of administration method often depends on the extent and location of the skin condition.

UVA Exposure and Dosing

Following psoralen administration, the patient's skin is exposed to UVA light. The intensity and duration of exposure are carefully calibrated. Modern PUVA lamps, such as those utilizing LEDs, offer more intense light, potentially reducing treatment time and allowing for weaker psoralen concentrations. Treatment doses are typically initiated based on the patient's skin type and gradually increased until a therapeutic response, often indicated by mild skin redness (erythema), is observed.

The initial UVA dose is determined by the patient's skin type and sensitivity. It is progressively increased, often by small increments (e.g., 10 seconds per session), until the skin exhibits a slight pinkness, signifying a phototoxic reaction. Once this response is achieved, the UVA dose is maintained consistently. Some clinics employ a pre-treatment test to determine the Minimum Phototoxic Dose (MPD) or Minimal Erythema Dose (MED) after psoralen ingestion, using this value as the baseline for subsequent treatment sessions.

Targeted Application

For localized patches of conditions like vitiligo, psoralen can be applied directly as drops onto the affected spots. This highly targeted approach minimizes systemic exposure and associated side effects. However, for more widespread conditions, oral psoralen or immersion therapy (like PUVA bath therapy) may be necessary.

Comparison with Narrowband UVB

UVB vs. PUVA

Narrowband ultraviolet B (UVB) phototherapy, particularly at 311 nanometers, has become a more common treatment for conditions like vitiligo, largely because it eliminates the need for psoralen and is generally easier to administer over larger body surface areas. However, PUVA therapy may retain an advantage for specific areas like the hands and legs.

Penetration Depth

The rationale for PUVA's potential superiority in certain regions lies in the differing penetration depths of UVA and UVB light. UVA penetrates deeper into the skin layers compared to UVB. Since the melanocytes responsible for skin pigmentation are located deeper in the dermis of the hands and legs, UVA's greater penetration may make PUVA more effective for treating pigmentary disorders in these areas. Narrowband UVB, conversely, is largely absorbed by the stratum corneum, the outermost skin layer.

Melanin Production

Melanin, the pigment that determines skin color, is produced by melanocytes. These cells possess receptors that detect UV light, triggering melanin synthesis. Melanin serves as a natural shield, protecting the underlying skin cells from UV-induced damage. The interplay between UV light, psoralen, and melanocyte stimulation is central to the therapeutic outcomes observed in PUVA therapy.

Side Effects and Complications

Acute Side Effects

When psoralen is administered orally for extensive skin areas, patients may experience acute side effects such as nausea and itching. For individuals sensitive to oral psoralen, alternative methods like PUVA bath therapy can be considered to mitigate these gastrointestinal and dermatological reactions.

Long-Term Risks

Prolonged or repeated use of oral PUVA therapy has been associated with an increased incidence of skin cancers, notably squamous cell carcinoma.^[7] This risk is attributed to the combined carcinogenic effects of UVA radiation and psoralen's interaction with DNA, which can lead to genomic instability.^{[citation needed]}

Carcinogenic Factors

The development of squamous cell skin cancer is considered the most significant complication of long-term PUVA therapy, particularly for psoriasis treatment. Both the non-ionizing radiation of UVA light and the psoralen molecule, which can intercalate into DNA, contribute to cellular damage and potentially increase the risk of malignant transformation. Careful monitoring and adherence to treatment protocols are essential to minimize these risks.

Historical Context

Ancient Origins

The therapeutic use of light-sensitive plants and sunlight dates back millennia. Ancient Egyptians, around 2000 BC, applied the juice of the plant Ammi majus to vitiligo patches, followed by sun exposure.^[8] Historical texts from the 13th century also describe similar treatments using a plant identified as A. majus, known to contain psoralen derivatives like bergapten and methoxsalen.^[9]

Early Phototherapy Devices

The foundation for modern phototherapy was laid in the late 19th century. Niels Ryberg Finsen developed early, bulky phototherapy apparatuses in the 1890s to treat skin diseases with UV light. By 1900, Gustave Trouvé had miniaturized these devices, creating portable light radiators for treating skin ailments.^[10]

The development of modern PUVA therapy gained momentum in the mid-20th century. In the 1940s, Abdel Monem El Mofty pioneered the use of crystalline methoxsalen (8-methoxypsoralen) combined with sunlight exposure for treating vitiligo. This clinical application marked a significant step toward the standardized PUVA protocols used today for various skin conditions. Chemically synthesized psoralen and advanced phototherapy equipment became widely available from the 1970s onwards.

External Resources

Dermatological Information

For further details on phototherapy and related skin treatments, consult resources from reputable dermatological organizations.

DermNet NZ: Phototherapy

Medication Information

Information regarding specific medications used in PUVA therapy, such as psoralen derivatives, can be found through pharmaceutical databases.

RxList: Oxsoralen-Ultra

Health Policy Guidelines

Guidelines on the medical necessity and coverage of light therapies for dermatologic conditions are often published by health insurance providers.

BCBSNC Medical Policy

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References

A full list of references for this article are available at the PUVA therapy Wikipedia page

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Important Notice Regarding Medical Information

This page has been generated by an Artificial Intelligence and is intended solely for informational and educational purposes. The content is derived from a snapshot of publicly available data and may not be entirely accurate, comprehensive, or current.

This content does not constitute medical advice. The information provided herein is not a substitute for professional medical consultation, diagnosis, or treatment. Always seek the advice of a qualified healthcare provider with any questions you may have regarding a medical condition or treatment. Never disregard professional medical advice or delay in seeking it because of information obtained from this resource.

The creators of this page are not liable for any errors or omissions, nor for any actions taken based on the information presented.

Illuminating Skin Health

💡 Dive in with Flashcard Learning! 💡

Overview ℹ️

☀️ Photochemotherapy Defined

🔬 Mechanism of Action

✨ Distinction from Photodynamic Therapy

Procedure ⚙️

💊 Psoralen Administration

💡 UVA Exposure and Dosing

💧 Targeted Application

Comparison with Narrowband UVB ⚖️

🆚 UVB vs. PUVA

⬆️ Penetration Depth

🎨 Melanin Production

Side Effects and Complications ⚠️

🤢 Acute Side Effects

📈 Long-Term Risks

🛡️ Carcinogenic Factors

Historical Context 📜

🏺 Ancient Origins

💡 Early Phototherapy Devices

Related Topics 🔗

🌿 Goeckerman Therapy

🌟 PUVA Lentigines

External Resources 🌐

📚 Dermatological Information

💊 Medication Information

🏥 Health Policy Guidelines

Teacher's Corner 🧑‍🏫

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References

📜 References

Feedback & Support 👍

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Disclaimer ⚠️

📜 Important Notice Regarding Medical Information

Dive in with Flashcard Learning!

Overview

Photochemotherapy Defined

Mechanism of Action

Distinction from Photodynamic Therapy

Procedure

Psoralen Administration

UVA Exposure and Dosing

Targeted Application

Comparison with Narrowband UVB

UVB vs. PUVA

Penetration Depth

Melanin Production

Side Effects and Complications

Acute Side Effects

Long-Term Risks

Carcinogenic Factors

Historical Context

Ancient Origins

Early Phototherapy Devices

Related Topics

Goeckerman Therapy

PUVA Lentigines

External Resources

Dermatological Information

Medication Information

Health Policy Guidelines

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Disclaimer

Important Notice Regarding Medical Information