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Dermatology Diagnosis

Keys To Differentiating Violaceous Discoloration On The Lower Legs And Feet

A 73-year-old male with well-controlled hypertension and diabetes mellitus presented with six months of an asymptomatic purple discoloration on the lower legs and feet. He denied any history of new medications or nonsteroidal anti-inflammatory drug (NSAID) use. The patient also noted no illicit drug use. 

The patient worked as a house painter and admitted to spending hours on his feet daily. He would also rest his shins against metal scaffolding when standing for prolonged periods of time. The patient denied any history of congestive heart failure or lower extremity swelling, and did not wear compression stockings. There was no pertinent surgical history. He denied fevers, chills, arthralgias, pruritus or pain associated with the lesions. The patient denied the use of any over-the-counter or prescription treatments prior to presentation. 

On physical exam, there were multiple non-blanchable petechiae along with dark reddish-brown macules coalescing into patches on the bilateral shins (see first photo above), lateral ankles and feet (see second photo above). There was 1+ pitting edema of the lower extremities bilaterally. There were no erosions or ulcerations on exam. The patient had bilateral dorsalis pedis and posterior tibial pulses. 

Key Questions To Consider 

1. What is included in the differential diagnosis? 

2. What is the most likely diagnosis of this patient’s rash? 

3. What are the key characteristics of this condition? 

4. What are the treatment recommendations for this condition? 

Answering The Key Diagnostic Questions 

1. The differential diagnosis would include cutaneous T-cell lymphoma, progressive pigmented purpuric dermatosis, lichen planus, stasis dermatitis, leukocytoclastic vasculitis and scurvy. 

2. Progressive pigmented purpuric dermatosis (Schamberg’s disease) 

3. The key characteristics were pinpoint, non-blanching petechiae and red-brown macules coalescing into patches in dependent areas of the lower extremities. 

4. First-line treatment options include leg elevation and compression garments. One may use midpotency topical steroids if the patient is symptomatic. Other treatment options include psoralen and UV-A (PUVA) therapy, narrow-band UV-B (nbUVB) therapy, pentoxifylline, cyclosporine, and rutoside with ascorbic acid.

Keys To The Differential Diagnosis 

The differential diagnosis includes cutaneous T-cell lymphoma, progressive pigmented purpuric dermatosis, lichen planus, stasis dermatitis, leukocytoclastic vasculitis and scurvy. 

Cutaneous T-cell lymphoma has a variety of clinical subtypes and presentations, but most often presents as asymptomatic, erythematous, atrophic and scaly plaques in photo-protected areas. An early and unusual presentation consists of a purpuric eruption similar to pigmented purpuric dermatosis. Key differences include widespread cutaneous involvement and pruritus lasting more than one year.1 Alternatively, pigmented purpuric dermatosis usually presents on the lower extremities with a possible history of lower extremity swelling or prolonged standing. 

It is important to note that cases of pigmented purpuric dermatosis may precede a diagnosis of cutaneous T-cell lymphoma so monitoring patients with long-standing lesions is key.2-4 Histologically, the two conditions can present with clonal lymphocytic populations and a vacuolar interface dermatitis. However, Pautrier microabscesses and lymphocyte extravasation into the epidermis align more with cutaneous T-cell lymphoma than pigmented purpuric dermatosis. 

Lichen planus typically presents as purple, polygonal, pruritic, planar papules on the extremities with an overlying white reticular pattern referred to as Wickham striae. Patients may also have mucosal and nail involvement.5 While these lesions are often on the extremities, they are usually raised and very pruritic. Alternatively, pigmented purpuric dermatosis may be pruritic but is often asymptomatic and flat. Additionally, Wickham striae are pathognomonic for lichen planus. Histopathology between the two entities may appear similar but pigmented purpuric dermatosis involves a diffuse lymphocytic infiltrate surrounding capillaries with extravasation of red blood cells, and lichen planus consists of a lymphocytic interface with wedge-shaped hypergranulosis, “saw tooth” rete ridges and Max Joseph spaces.5 

Venous stasis dermatitis is another consideration when dealing with a lower extremity violaceous eruption. Similar to pigmented purpuric dermatosis, venous insufficiency and swelling are contributing factors. Lesions may occur on the shins but are more common on the medial malleolus. Erythematous and hyperpigmented patches are more typical than violaceous to golden-brown lesions.6 Furthermore, patients may present with erosions or ulcerations, which does not occur in cases of pigmented purpuric dermatosis. 

The histopathology of stasis dermatitis will demonstrate a lobular proliferation of blood vessels in the superficial dermis, extravasated red blood cells and variable pigment incontinence with hemosiderin-laden macrophages depending on the stage of disease.7 Variable epidermal changes such as hyperplasia, spongiosis and parakeratosis may also be present.7 

Another differential diagnosis is the broad category of cutaneous leukocytoclastic vasculitis. The hallmark clinical findings are palpable purpuric lesions though some lesions may not be palpable and necrosis may also be evident.8 Similar to pigmented purpuric dermatosis, these lesions are often on the lower extremities but are more likely to be widespread. Other organs can be involved aside from the skin. Thus, a more comprehensive workup is necessary in comparison to the workup for pigmented purpuric dermatosis. Patients may also have a temporal relationship to a new medication, illicit drug use or a recent illness although idiopathic variants are the most common. 

Histopathology also distinguishes the two entities as vasculitic lesions. Histopathology will demonstrate small, medium or large vessel compromise with fibrinoid necrosis of the vessel wall and surrounding neutrophilic leukocytoclasia and karyorrhexis.8 

Lastly, scurvy is a less common but important diagnosis to consider with lower extremity purpuric lesions. Distinguishing historical and clinical findings include the patient’s diet (often limited), perifollicular-based lesions and corkscrew hairs. Histopathology is also less inflammatory and consists more of a corkscrew-shaped hair follicle with hyperkeratosis and follicular plugging.9 

What Are Pigmented Purpuric Dermatoses? 

Pigmented purpuric dermatosis encompasses a difficult to treat group of vascular disorders that are chronic and have a variety of presentations. Lesions are more commonly asymptomatic and may involve petechial, pigmented or red-brown macules or patches that often present on the lower extremities.10 This broad category of dermatoses consists of five main subtypes: progressive pigmented purpuric dermatosis (Schamberg’s disease), purpura annularis telangiectodes (Majocchi’s disease), lichen aureus, pigmented purpuric dermatosis of Gougerot-Blum and eczematid-like purpura of Doucas-Kapetanakis.11 See “Pertinent Characteristics Of The Subgroups Of Pigmented Purpuric Dermatoses” above. 

The exact cause of pigmented purpuric dermatosis is unknown. One theory suggests gradual alteration of epitheliotropic T-cells. Capillary dilation and fragility are also possible causes. Although the exact mechanism is unknown, factors associated with pigmented purpuric dermatosis include venous hypertension, prolonged standing, hypertension, diabetes, thyroid disease, venous stasis, strenuous exercise and medications (i.e. statins, beta-blockers, NSAIDs, and aspirin).11,12 

Histopathological findings include epidermal changes (hyperkeratosis, parakeratosis, or acanthosis), perivascular lymphocytic infiltration, dermal hemosiderin deposition, endothelial swelling, spongiosis, exocytosis (erythrocyte and lymphocyte), and lichenoid lymphocytic infiltration.10 Lymphocytic vasculitis may also be present.10,11 

Current Treatment Options For Pigmented Purpuric Dermatoses 

Progressive pigmented purpuric dermatosis and pigmented purpuric dermatosis in general are difficult to treat. Spontaneous resolution after months may occur but recurrences are frequent.1,13 Current treatments focus on treating symptoms (i.e. pruritus) if present but no single therapy or combination treatment demonstrates superiority in the literature.11 

Topical medium- and high-potency corticosteroids are first-line therapy and help reduce itch, resulting in clearance of lesions in some cases.12 Topical calcineurin inhibitors are also beneficial and may be better for long-term use in recurrent cases due to a better safety profile compared to topical corticosteroids.12 Phototherapy is another useful alternative for those who do not respond to steroid therapy. Both psoralen UV-A (PUVA) and narrow-band UV-B (nbUVB) have documented success in the literature in as little as seven (PUVA) and 24 (nbUVB) treatment sessions.12,14 

Oral therapies include pentoxifylline 400 mg as a monotherapy two to three times daily for two to three months, or in combination with prostacyclins or oral corticosteroids. High doses of vitamin C (500 mg daily or twice daily) combined with 50 mg of rutoside/rutin (a flavonoid glycoside) daily strengthens vascular endothelial function and reduces vascular permeability.12 Other less studied therapies include oral griseofulvin, colchicine, methotrexate and cyclosporin.12 

Final Notes 

A thorough history and physical exam are key to differentiate the above diagnoses. With regard to pigmented purpuric dermatosis, it is imperative that clinicians identify if there is venous hypertension or prolonged standing, and determine if the patient recently took any new medications, including NSAIDs. 

Although this condition can be hard to treat, one should reassure the patient and take a conservative approach. Despite the rarity and lack of clear evidence connecting pigmented purpuric dermatosis to cutaneous T-cell lymphoma, clinicians can routinely monitor these patients and only adopt a high index of suspicion in cases of diffuse lesion distribution and abnormal histology.  

Dr. Ashack is an Assistant Professor at the Michigan State University College of Human Medicine and is in private practice in Grand Rapids, Mich. 

Dermatology Diagnosis
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By Kurt A. Ashack, MHS, MD
References

1. Riyaz N, Sasidharanpillai S, Abdul Latheef EN, Davul H. Ashraf F. Pigmented purpuric dermatosis or mycosis fungoides: a diagnostic dilemma. Indian Dermatol Online J. 2016;7:183-185. 

2. Ladrigan MK, Poligone B. The spectrum of pigmented purpuric dermatosis and mycosis fungoides: atypical T-cell dyscrasia. Cutis. 2014;94(6):297-300. 

3. Barnhill RL, Braverman IM. Progression of pigmented purpura-like eruptions to mycosis fungoides: report of three cases. J Am Acad Dermatol. 1988;19(1 Pt 1):25-31. 

4. Georgala S, Katoulis AC, Symeonidou S, Georgala C, Vayopoulos G. Persistent pigmented purpuric eruption associated with mycosis fungoides: a case report and review of the literature. J Eur Acad Dermatol Venereol. 2001;15(1):62-64. 

5. Tziotzios C, Lee JYW, Brier T, et al. Lichen planus and lichenoid dermatoses: Clinical overview and molecular basis. J Am Acad Dermatol. 2018;79(5):789-804. 

6. Sundaresan S, Migden MR, Silapunt S. Stasis dermatitis: pathophysiology, evaluation, and management. Am J Clin Dermatol. 2017;18(3):383-390. 

7. Weaver J, Billings SD. Initial presentation of stasis dermatitis mimicking solitary lesions: a previously unrecognized clinical scenario. J Am Acad Dermatol. 2009;61(6):1028-1032. 

8. Frumholtz L, Laurent-Roussel S, Lipsker D, Terrier B. Cutaneous vasculitis: review on diagnosis and clinicopathologic correlations. Clin Rev Allergy Immunol. 2020. Online ahead of print. Available at: https://neuro.unboundmedicine. com/medline/citation/32378145/Cutaneous_ Vasculitis:_Review_on_Diagnosis_and_Clinicopathologic_Correlations. Published May 6, 2020. Accessed August 31, 2020. 

9. Lipner S. A classic case of scurvy. Lancet. 2018;392(10145):431. 

10. Huang YK, Lin CK, Wu YH. The pathological spectrum and clinical correlation of pigmented purpuric dermatosis-A retrospective review of 107 cases. J Cutan Pathol. 2018;45(5):325-332. 

11. Kim DH, Seo SH, Ahn HH, Kye YC, Choi JE. Characteristics and clinical manifestations of pigmented purpuric dermatosis. Ann Dermatol. 2015;27(4):404-410. 

12. Martinez Pallas I, Conejero Del Mazo R, Lezcano Biosca V. Pigmented purpuric dermatosis: a review of the literature. Actas Dermosifiliogr. 2020;111(3):196-204. 

13. Sharma L , Gupta S. Clinicoepidemiological study of pigmented purpuric dermatoses. Indian Dermatol Online J. 2012;3:17-20. 

14. Coulombe J, Jean SE, Hatami A, et al. Pigmented purpuric dermatosis: clinicopathologic characterization in a pediatric series. Pediatr Dermatol. 2015;32(3):358-362. 

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