Background
Pseudolymphoma is not a specific disease but rather an inflammatory response to known or unknown stimuli that results in a lymphomatous-appearing but benign accumulation of inflammatory cells.[1] In cutaneous pseudolymphoma, resemblance to lymphoma is usually most apparent histologically, but some examples may also mimic lymphoma clinically. When known, the inciting agent should be included within the diagnosis of cutaneous pseudolymphoma. The term pseudolymphoma without modification should be reserved for idiopathic cases.
Localized, nodular pseudolymphomas are more common and typically mimic B-cell lymphoma (for further discussion, see Lymphocytoma Cutis). A variety of specific diseases are sometimes referred to as pseudolymphomas simply because they may resemble lymphoma. These disorders often show broad patches and plaques and often mimic cutaneous T-cell lymphoma. Examples include actinic reticuloid, lymphomatoid contact dermatitis, and lymphomatoid drug eruptions.[2] Note the images below.
Pseudolymphomatous drug eruption due to captopril, marked by erythematous to purple papules, patches, and plaques. 
This erythrodermic pseudolymphoma (T-cell pattern) typifies drug-induced pseudolymphoma, which is most often secondary to anticonvulsant therapy. Pathophysiology
In persons with pseudolymphoma, lymphocytes and other inflammatory cells are recruited to the skin in response to known or unknown stimuli. Most cases are idiopathic. Cases of cutaneous pseudolymphoma with known etiology include reactions to tattoo dyes, jewelry (especially gold), insect bites, medications,[3] folliculitis, trauma, infections, vaccinations,[4] and contactants. A discrete subset of pseudolymphoma, borrelial lymphocytoma, primarily occurs in Europe in areas endemic for the tick Ixodes ricinus. Borrelial lymphocytoma is a response to infection by Borrelia burgdorferi subsp afzelius conferred by a tick bite. Another subset of pseudolymphoma is the result of an unusual systemic response to medications, typically anticonvulsants (see Drug-Induced Pseudolymphoma Syndrome).
Epidemiology
Frequency
International
No frequency data are available for cutaneous pseudolymphoma; the condition is uncommon but not rare.
Mortality/Morbidity
Pseudolymphoma is not associated with mortality. Localized variants rarely result in morbidity other than minor pain or pruritus. Rare cases of cutaneous pseudolymphoma have been described in which the pseudolymphoma has evolved into cutaneous lymphoma.
Race
Although 90% of reported patients with pseudolymphoma are white, racial predilection has not been established.
Sex
In reported cases of localized pseudolymphoma, the female-to-male ratio is approximately 2:1. No significant epidemiologic data are available regarding entities in the T-cell pattern pseudolymphoma spectrum.
Age
Individuals of any age may be affected, but localized, nodular pseudolymphoma is most common in early life. The mean age of onset is 34 years. Two thirds of patients are younger than 40 years at the time of biopsy. Approximately 8% of cases involve patients younger than 18 years. Borrelial pseudolymphoma is more common in children than in adults.
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Braun RP, French LE, Feldmann R, Chavaz P, Saurat JH. Cutaneous pseudolymphoma, lymphomatoid contact dermatitis type, as an unusual cause of symmetrical upper eyelid nodules. Br J Dermatol. Aug 2000;143(2):411-4. [Medline].
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