30: Parapsoriasis and Pityriasis Lichenoides

Question 1

What are the clinical features of parapsoriasis?

Answer 1

• Cutaneous Findings: Oval or irregularly shaped patches or very thin plaques that are asymptomatic or mildly pruritic. Most lesions are larger than 5 cm, often measuring more than 10 cm in diameter. Found mainly on the ‘bathing trunk’ and flexural areas. Light red-brown or salmon pink, covered with small and scanty scales, may appear finely wrinkled (cigarette paper wrinkling).

Types of Parapsoriasis: Poikiloderma (Atrophy + mottled pigmentation + telangiectasia), Retiform Parapsoriasis (Extensive eruption of scaly macules and papules in a net-like pattern), Small Plaque Parapsoriasis (Round or oval discrete patches, mainly on the trunk, less than 5 cm in diameter, asymptomatic), Digitate Dermatosis (More than 5 cm finger-shaped lesions with yellowish or fawn-colored appearance).

Question 2

What is the epidemiology of parapsoriasis?

Answer 2

• Affects middle-aged and older people, with peak incidence in the fifth decade. Lesions arise in childhood and may be associated with pityriasis lichenoides. Male preponderance: 3:1. Occurs in all racial groups and geographic regions.

Question 3

What complications can arise from large plaque parapsoriasis (LPP) and small plaque parapsoriasis (SPP)?

Answer 3

• LPP and SPP can occasionally develop impetiginization secondary to excoriations. Increased risk for cardiovascular disease such as acute myocardial infarction and stroke. Increased risk for subsequent hematologic and nonhematologic malignancies and increased mortality.

Question 4

What is the etiology and pathogenesis of large plaque parapsoriasis (LPP)?

Answer 4

• Some cases of LPP are a monoclonal proliferation of SALT T cells that can traffic between the skin and extracutaneous sites. Mycosis Fungoides (MF) is associated with SALT, and trafficking of MF tumor cells has been detected in early stage LPP. Structural and numerical chromosomal abnormalities are found in peripheral blood mononuclear cells in LPP.

Question 5

What is the disease spectrum associated with parapsoriasis?

Answer 5

• The parapsoriasis group of diseases includes: LPP, MF, Large Cell Lymphoma. A unifying feature is that they appear to be cutaneous T-cell lymphoproliferative disorders. There is an increasing gradient of T-cell clonal density due to mutations, leading to LPP progression to MF. Clonal Dermatitis: A model where MF becomes the final common pathway for the clonal evolution of neoplastic T cells from polyclonal SALT T-cell populations.

Question 6

What are the clinical features of parapsoriasis, particularly in terms of lesion characteristics and distribution?

Answer 6

• Lesion Shape: Oval or irregularly shaped patches or very thin plaques.
• Symptoms: Asymptomatic or mildly pruritic.
• Size: Most lesions are larger than 5 cm, often measuring more than 10 cm in diameter.
• Location: Primarily found on the ‘bathing trunk’ and flexural areas.
• Appearance: Light red-brown or salmon pink, covered with small and scanty scales, may exhibit ‘cigarette paper’ wrinkling (epidermal atrophy).

Question 7

A patient with parapsoriasis has lesions with atrophy, mottled pigmentation, and telangiectasia. What is this condition called, and what are its components?

Answer 7

This condition is called poikiloderma or poikiloderma atrophicans vasculare. Its components are atrophy, mottled pigmentation, and telangiectasia.

Question 8

A patient with parapsoriasis has lesions that are less than 5 cm in diameter and covered with fine, moderately adherent scales. What is the diagnosis, and what is the general health impact of this condition?

Answer 8

The diagnosis is small plaque parapsoriasis (SPP). The general health of the patient is unaffected.

Question 9

A patient with parapsoriasis has lesions in a net-like or zebra-stripe pattern that eventually become poikilodermatous. What is this rare condition called?

Answer 9

This rare condition is called retiform parapsoriasis.

Question 10

A 45-year-old male presents with oval patches on his trunk that are asymptomatic and measure over 10 cm in diameter. The lesions are salmon pink with scanty scales. What is the most likely diagnosis, and what are the characteristic features of this condition?

Answer 10

The most likely diagnosis is large plaque parapsoriasis (LPP). Characteristic features include oval or irregularly shaped patches larger than 5 cm, often over 10 cm, found mainly on the trunk and flexural areas. The lesions are light red-brown or salmon pink with scanty scales and may appear finely wrinkled (‘cigarette paper’ wrinkling).

Question 11

A patient presents with poikilodermatous lesions and a history of digitate dermatosis. What is the likely diagnosis, and what are the distinguishing features of digitate dermatosis?

Answer 11

The likely diagnosis is large plaque parapsoriasis (LPP). Digitate dermatosis is characterized by finger-shaped lesions more than 5 cm in size, yellowish or fawn-colored, following lines of cleavage of the skin, giving the appearance of a ‘hug that left fingerprints.’

Question 12

A patient with suspected large plaque parapsoriasis (LPP) has lesions with poikilodermatous features. What are the components of poikiloderma, and how do they manifest in LPP?

Answer 12

The components of poikiloderma are atrophy, mottled pigmentation, and telangiectasia. In LPP, these features manifest as poikilodermatous lesions.

Question 13

A patient with parapsoriasis has lesions that are finger-shaped and follow the lines of cleavage of the skin. What is the clinical term for this presentation, and what is its significance?

Answer 13

The clinical term for this presentation is digitate dermatosis. It is significant as a distinctive feature of large plaque parapsoriasis (LPP).

Question 14

A patient with suspected large plaque parapsoriasis (LPP) has lesions that are asymptomatic and covered with scanty scales. What is the typical color of these lesions, and how does it aid in diagnosis?

Answer 14

The typical color of LPP lesions is light red-brown or salmon pink. This aids in diagnosis by distinguishing LPP from other dermatological conditions.

Question 15

A patient with parapsoriasis has lesions that are poikilodermatous and associated with an increased risk of hematologic malignancies. What is the clinical significance of this finding?

Answer 15

The clinical significance is that poikilodermatous lesions in parapsoriasis, particularly large plaque parapsoriasis (LPP), may indicate an increased risk of progression to mycosis fungoides (MF) or other hematologic malignancies.

Question 16

A patient with large plaque parapsoriasis (LPP) is found to have structural chromosomal abnormalities in peripheral blood mononuclear cells. What does this suggest about the disease’s pathogenesis?

Answer 16

This suggests that LPP may involve monoclonal proliferation of SALT T cells with chromosomal abnormalities, indicating a potential progression to mycosis fungoides (MF).

Question 17

A patient with parapsoriasis has lesions that follow the lines of cleavage of the skin. What is this specific presentation called, and in which type of parapsoriasis is it seen?

Answer 17

This presentation is called digitate dermatosis, seen in large plaque parapsoriasis (LPP).

Question 18

A patient with parapsoriasis has lesions that are asymptomatic and covered with fine, moderately adherent scales. What is the most likely diagnosis, and what is the typical distribution of these lesions?

Answer 18

The most likely diagnosis is small plaque parapsoriasis (SPP). The lesions are typically distributed on the trunk.

Question 19

What are the histopathological features of early LPP lesions?

Answer 19

Early LPP lesions are characterized by: - Mild acanthosis - Slight hyperkeratosis with spotty parakeratosis - Dermal lymphocytic infiltrate that tends to be perivascular and scattered.

Question 20

How does advanced LPP differ from early LPP in terms of histopathology?

Answer 20

Advanced LPP is characterized by: - Interface infiltrate with definite epidermotropism - Scattered lymphocytes, sometimes in groups, associated with mild spongiosis - Poikilodermatous lesions showing atrophic epidermis, dilated blood vessels, and melanophages.

Question 21

What are the distinguishing features of SPP compared to MF?

Answer 21

SPP is characterized by: - Mild spongiotic dermatitis with focal areas of hyperkeratosis, parakeratosis, scale crust, and exocytosis - Mild superficial perivascular lymphohistiocytic infiltrate and dermal edema - No progression of histologic features over time, predominantly CD4+ T-cell infiltrate.

Question 22

What are the key differences between SPP and psoriasis?

Answer 22

Key differences include: - SPP lacks the auspitz sign, micaceous scale, nail pits, and typical psoriatic lesions on the scalp, elbows, and knees - SPP does not present with herald patches as seen in pityriasis rosea.

Question 23

What clinical features are associated with LPP?

Answer 23

LPP is associated with: - Thicker, small plaques - Asymmetric distribution and irregular shape of lesions - Lesions that are less discrete and often poikilodermatous.

Question 24

What are the distinguishing histopathological features of early LPP lesions compared to advanced LPP lesions?

Answer 24

Early LPP lesions: - Mildly acanthotic and slightly hyperkeratotic with spotty parakeratosis. - Dermal lymphocytic infiltrate tends to be perivascular and scattered.

Advanced LPP lesions: - Interface infiltrate with definite epidermotropism. - Invading lymphocytes may be scattered singly or in groups, sometimes associated with mild spongiosis. - Poikilodermatous lesions show atrophic epidermis, dilated blood vessels, and melanophages.

Question 25

How can one differentiate between SPP and MF based on clinical presentation?

Answer 25

- **SPP**: Mild spongiotic dermatitis with focal areas of hyperkeratosis, parakeratosis, scale crust, and exocytosis. Dermis shows mild superficial perivascular lymphohistiocytic infiltrate and dermal edema. No progression of histologic features over time. Predominantly CD4+ T-cell infiltrate. - **MF**: Well-developed, moderate to thick, small plaques. Features incompatible with SPP, may show poikilodermatous features not seen in SPP.

Question 26

What are the key clinical features that differentiate SPP from psoriasis?

Answer 26

- **SPP**: No auspitz sign, micaceous scale, or nail pits. Typical lesions do not involve the scalp, elbows, and knees. - **Psoriasis**: Presence of auspitz sign, micaceous scale, and nail pits. Involves typical psoriatic lesions in the scalp, elbows, and knees.

Question 27

What are the common immunological findings in both LPP and MF?

Answer 27

- Predominance of **CD4+ T-cell subsets**. Frequent **CD7 antigen deficiency**. Widespread epidermal expression of **Class II human leukocyte antigen D-related (HLA-DR)**.

Question 28

A patient with suspected large plaque parapsoriasis (LPP) undergoes a biopsy. What histological features would support the diagnosis?

Answer 28

Histological features of LPP include mildly acanthotic and slightly hyperkeratotic epidermis with spotty parakeratosis in early lesions, and interface infiltrate with definite epidermotropism in advanced lesions.

Question 29

A patient with suspected mycosis fungoides (MF) has a predominance of CD4+ T-cell subsets and CD7 antigen deficiency. What other histological feature is commonly seen in both LPP and MF?

Answer 29

Both LPP and MF commonly show widespread epidermal expression of Class II human leukocyte antigen D-related (HLA-DR).

Question 30

A patient with small plaque parapsoriasis (SPP) is concerned about progression to mycosis fungoides (MF). What clinical and pathological features would help differentiate SPP from MF?

Answer 30

SPP lesions are not thicker than patches or very thin plaques, while MF may present with well-developed, moderate to thick plaques. Pathologically, SPP shows mild spongiotic dermatitis with focal hyperkeratosis and parakeratosis, while MF may show epidermotropism and CD7 antigen deficiency.

Question 31

A patient with suspected mycosis fungoides (MF) presents with patch lesions. What scoring system is used to confirm MF, and what score indicates unequivocal MF?

Answer 31

A scoring system is used where patients presenting with patch lesions scoring 4 points or more are diagnosed with unequivocal MF.

Question 32

A patient with parapsoriasis has lesions that are larger, asymmetrically distributed, and irregularly shaped. What type of parapsoriasis is this, and how does it differ from small plaque parapsoriasis (SPP)?

Answer 32

This is large plaque parapsoriasis (LPP). It differs from SPP in that LPP lesions are larger, asymmetrically distributed, and irregularly shaped, while SPP lesions are smaller and more discrete.

Question 33

A patient with pityriasis lichenoides has lesions that coexist with papulovesicular patches favoring the lower extremities. What differential diagnosis should be considered?

Answer 33

The differential diagnosis should include nummular dermatitis, which presents with papulovesicular coin-shaped patches favoring the lower extremities.

Question 34

A patient with suspected mycosis fungoides (MF) has a biopsy showing CD4+ T-cell subsets and widespread epidermal expression of HLA-DR. What does this indicate about the disease's immunopathology?

Answer 34

This indicates that MF involves a predominance of CD4+ T-cell subsets and widespread epidermal expression of Class II human leukocyte antigen D-related (HLA-DR), reflecting an immune-mediated pathogenesis.

Question 35

What does a biopsy showing CD4+ T-cell subsets and widespread epidermal expression of HLA-DR indicate in suspected mycosis fungoides (MF)?

Answer 35

It indicates that MF involves a predominance of CD4+ T-cell subsets and widespread epidermal expression of Class II human leukocyte antigen D-related (HLA-DR), reflecting an immune-mediated pathogenesis.

Question 36

What histological findings would confirm the diagnosis of small plaque parapsoriasis (SPP)?

Answer 36

Histological findings in SPP include mild spongiotic dermatitis with focal areas of hyperkeratosis, parakeratosis, scale crust, and exocytosis, with a mild superficial perivascular lymphohistiocytic infiltrate.

Question 37

What other histological features might be present in advanced lesions of mycosis fungoides (MF)?

Answer 37

Advanced lesions may show atrophic epidermis, dilated blood vessels, melanophages, and a predominance of CD4+ T-cell subsets with CD7 antigen deficiency.

Question 38

What are the management strategies for patients with Small-Plaque Parapsoriasis (SPP)?

Answer 38

- Patients should be reassured and may forego treatment. - The disease may be treated with: - Emollients - Topical tar preparations - Topical corticosteroids - BBUVB or NBUVB - Patients should initially be examined every 3 to 6 months and subsequently every year.

Question 39

What treatment is recommended for patients with Large-Plaque Parapsoriasis (LPP)?

Answer 39

- Requires more aggressive therapy: - High-potency topical corticosteroids with phototherapy (broadband UVB, narrowband UVB, low-dose UVA, or PUVA). - Goal of treatment: suppress the disorder to prevent possible progression to overt MF. - Localized lesions may respond to excimer laser (308 nm). - Patients should be examined every 3 months initially and every 6 months to 1 year subsequently. - Repeated multiple biopsies of suspicious lesions should be performed.

Question 40

What is the epidemiology of Pityriasis Lichenoides?

Answer 40

- Affects all racial and ethnic groups in all geographic regions. - More common in children and young adults. - Seasonal variation in onset favoring fall and winter. - Male predominance of 1.5:1 to 3:1. - PLC is 3 to 6 times more common than PLEVA.

Question 41

What are the clinical features of Pityriasis Lichenoides?

Answer 41

- **Cutaneous Findings**: - PLC and PLEVA exist on a clinicopathologic continuum; patients may exhibit a mixture of acute and chronic lesions. | Type | Description | |------|-------------| | PLC | Recurrent crops of erythematous scaly papules that spontaneously regress over several weeks to months. | | PLEVA | Recurrent crops of erythematous papules that develop crusts, vesicles, pustules, or erosions before spontaneously regressing within weeks. | | PLUH/FUMHD | Purpuric papulonodules with central ulcers up to a few centimeters in diameter. | - Lesions tend to concentrate on the trunk and proximal extremities, but can occur anywhere on the skin or mucous membranes.

Question 42

What are the potential complications associated with Pityriasis Lichenoides?

Answer 42

- All forms can result in postinflammatory hypopigmentation or hyperpigmentation. - Chronic lesions rarely lead to scars. - Acute lesions result in deeper dermal injury, often leaving varioliform (smallpox-like) scars. - Lesions in various stages of evolution impart a polymorphous appearance characteristic of pityriasis lichenoides.

Question 43

What is the prognosis for a patient with small plaque parapsoriasis (SPP) treated with topical corticosteroids and phototherapy?

Answer 43

The prognosis is generally good, and the disease may not require treatment. Patients should initially be examined every 3 to 6 months and subsequently every year.

Question 44

What forms of pityriasis lichenoides are most likely to result in postinflammatory hypopigmentation?

Answer 44

All forms of pityriasis lichenoides can result in postinflammatory hypopigmentation or hyperpigmentation.

Question 45

How does pityriasis lichenoides chronica (PLC) differ from its acute counterpart?

Answer 45

PLC lesions are scaly papules that regress over weeks to months, while PLEVA lesions develop crusts, vesicles, pustules, or erosions and regress within weeks.

Question 46

What is the goal of treatment for patients with large plaque parapsoriasis (LPP)?

Answer 46

The goal of treatment is to suppress the disorder and prevent progression to overt mycosis fungoides (MF).

Question 47

What is the characteristic appearance of pityriasis lichenoides due to lesions in various stages of evolution?

Answer 47

The characteristic appearance is polymorphous due to lesions in various stages of evolution. Acute lesions may result in deeper dermal injury and resolve with varioliform (smallpox-like) scars.

Question 48

What does seasonal variation in lesion onset suggest about the epidemiology of pityriasis lichenoides?

Answer 48

It suggests that pityriasis lichenoides has a seasonal variation in onset, which is more common in fall and winter.

Question 49

What form of pityriasis lichenoides resolves within weeks, and how does it differ from the chronic form?

Answer 49

This is pityriasis lichenoides et varioliformis acuta (PLEVA). It differs from the chronic form, pityriasis lichenoides chronica (PLC), in that PLEVA lesions resolve within weeks, while PLC lesions regress over weeks to months.

Question 50

What is the most common complication associated with PLEVA?

Answer 50

Secondary infection is the most common complication associated with PLEVA, which can lead to high fever, malaise, myalgia, arthralgia, gastrointestinal, and central nervous system symptoms, and may be fatal.

Question 51

What are the clinical features of PLC and PLEVA?

Answer 51

PLC and PLEVA are largely considered clinically benign disorders without significant linkage to lymphomas or other malignancies.

Question 52

What are the potential viral associations with PLEVA?

Answer 52

PLEVA may be associated with Toxoplasma gondii, Epstein-Barr virus, cytomegalovirus, varicella-zoster virus, parvovirus B19, human herpesvirus-8, and HIV.

Question 53

What is the predominant T-cell type found in PLC?

Answer 53

In PLC, CD4+ T cells predominate and express FoxP3, suggesting a regulatory T-cell phenotype, with dominant T-cell clonality in a minority of patients.

Question 54

What is the hallmark of lymphomatoid papulosis?

Answer 54

The hallmark of lymphomatoid papulosis is the presence of large CD30+ atypical lymphoid cells, which are typically CD4+ and often lack 1 or more mature T-cell antigens such as CD2, CD3, and CD5.

Question 55

What is the typical clinical course of PLEVA?

Answer 55

PLEVA typically has a variable clinical course characterized by recurrent crops of lesions that spontaneously resolve within a few months, but can persist for years.

Question 56

What is the mainstay of traditional therapy for PLEVA?

Answer 56

The mainstay of traditional therapy for PLEVA has been a combination of topical corticosteroids and phototherapy, with tetracyclines, erythromycin, and azithromycin used primarily for their anti-inflammatory effects.

Question 57

What are the common complications associated with PLEVA and PLC?

Answer 57

- **PLEVA**: High fever, malaise, myalgia, arthralgia, gastrointestinal, and central nervous system symptoms. May be fatal. - **PLC**: Low-grade fever, malaise, headache, and arthralgia. Both are largely considered clinically benign disorders without significant linkage to lymphomas or other malignancies.

Question 58

What are the key differences in the etiology and pathogenesis of PLC and PLEVA?

Answer 58

- **PLC**: - CD4+ T cells predominate, expressing FoxP3, suggestive of a regulatory T-cell phenotype. - Dominant T-cell clonality in a minority of patients. - **PLEVA**: - CD8+ T cells expressing cytotoxic proteins (TIA-1) and granzyme B predominate. - Dominant T-cell clonality in half of patients.

Question 59

How does the clinical course and prognosis of PLEVA compare to that of PLC?

Answer 59

- **PLEVA**: Typically has a shorter duration and is characterized by recurrent crops of lesions that may spontaneously resolve within a few months. - **PLC**: May persist for years and has a variable clinical course.

Question 60

What are the main management strategies for PLC and PLEVA?

Answer 60

- **Topical corticosteroids** and **phototherapy** are the mainstay of treatment. - **Antibiotics** (e.g., tetracyclines, erythromycin, azithromycin) are used for their anti-inflammatory effects. - **Photodynamic therapy** has been successfully used for PLC. - More severe individual lesions may require more systemic therapy.

Question 61

What does a reduction in CD1a+ antigen-presenting dendritic cells in the epidermis suggest about the pathogenesis of pityriasis lichenoides?

Answer 61

This finding suggests a reduction in Langerhans cells within the central epidermis of lesions, which may play a role in the pathogenesis of pityriasis lichenoides.

Question 62

What are the hallmark features of lymphomatoid papulosis, and how does it relate to pityriasis lichenoides?

Answer 62

The hallmark features are large CD30+ atypical lymphoid cells, typically CD4+ and often lacking mature T-cell antigens. Lymphomatoid papulosis and pityriasis lichenoides both exhibit dominant T-cell clonality and spontaneous resolution of papular lesions.

Question 63

What is the primary purpose of tetracycline treatment for a patient with pityriasis lichenoides?

Answer 63

The primary purpose of tetracycline treatment is for its anti-inflammatory effects.

Question 64

What does it suggest if pityriasis lichenoides and lymphomatoid papulosis coexist in the same patient?

Answer 64

This suggests that pityriasis lichenoides and lymphomatoid papulosis can coexist in the same patient, either concurrently or serially, and both exhibit dominant T-cell clonality.

Question 65

What is the likely complication for a patient with pityriasis lichenoides who develops high fever, myalgia, and central nervous system symptoms?

Answer 65

The likely complication is febrile ulceronecrotic Mucha-Habermann disease (FUMHD), a severe form of PLEVA. It may be fatal and is characterized by high fever, malaise, myalgia, arthralgia, and systemic symptoms.

Question 66

What condition is suggested by a biopsy showing CD8+ T cells expressing cytotoxic proteins (TIA-1 and granzyme B)?

Answer 66

This suggests pityriasis lichenoides et varioliformis acuta (PLEVA). Its pathogenesis involves a variably clonal cytotoxic memory T-cell lymphoproliferative response to one or more foreign antigens.

Question 67

What does dominant T-cell clonality in pityriasis lichenoides suggest about the disease's pathogenesis?

Answer 67

Dominant T-cell clonality suggests a clonal cytotoxic memory T-cell lymphoproliferative response, which may indicate a potential progression to lymphomatoid papulosis or other lymphoproliferative disorders.

Question 68

What is the primary mechanism of action for erythromycin in the treatment of pityriasis lichenoides?

Answer 68

The primary mechanism of action for erythromycin in pityriasis lichenoides is its anti-inflammatory effect.

Question 69

What does the presence of CD8+ T cells expressing cytotoxic proteins in pityriasis lichenoides suggest about the disease's immunopathology?

Answer 69

This suggests that pityriasis lichenoides involves a cytotoxic T-cell response, with CD8+ T cells expressing cytotoxic proteins such as TIA-1 and granzyme B.

Question 70

For which form of pityriasis lichenoides is photodynamic therapy most effective?

Answer 70

Photodynamic therapy has been used successfully for pityriasis lichenoides chronica (PLC).

Question 71

What is the clinical significance of large CD30+ atypical lymphoid cells in lymphomatoid papulosis?

Answer 71

Large CD30+ atypical lymphoid cells are a hallmark of lymphomatoid papulosis.

Question 72

What is the clinical significance of large CD30+ atypical lymphoid cells in lymphomatoid papulosis?

Answer 72

Large CD30+ atypical lymphoid cells are a hallmark of lymphomatoid papulosis. Despite their atypical appearance, the disease often resolves spontaneously and is considered clinically benign.