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Key Features

Essentials of Diagnosis

  • Localized or generalized erythematous scaling plaques

  • Sometimes associated with pruritus, lymphadenopathy

  • Distinctive histology

General Considerations

  • A cutaneous T cell lymphoma that begins on the skin and may remain there for years or decades (so-called mycosis fungoides)

  • Certain medications (including selective serotonin reuptake inhibitors) and photoallergy may produce eruptions clinically and histologically identical to those of mycosis fungoides, so this possibility must always be considered

  • Lymph node enlargement may be due to benign expansion of the node (dermatopathic lymphadenopathy) or by specific involvement with mycosis fungoides

Clinical Findings

Symptoms and Signs

  • Localized or generalized erythematous patches or plaques, usually on the trunk

  • Plaques are almost always over 5 cm in diameter

  • Pruritus is a frequent complaint and can be severe

  • The lesions often begin as nondescript or nondiagnostic patches, and it is not unusual for the patient to have skin lesions for more than a decade before the diagnosis can be confirmed

  • Follicular involvement with hair loss is characteristic of mycosis fungoides

  • In more advanced cases, tumors appear

  • Local or diffuse lymph node enlargement may be due to

    • Benign expansion of the node (dermatopathic lymphadenopathy)

    • Involvement with mycosis fungoides

Differential Diagnosis

  • Psoriasis

  • Drug eruption

  • Photoallergy

  • Atopic dermatitis (eczema)

  • Syphilis

  • Tinea corporis (body ringworm)


Laboratory Tests

  • Circulating malignant T cells (Sézary cells) can be detected in the blood (T cell gene rearrangement test)

  • Eosinophilia may be present

Diagnostic Procedures

  • Diagnosis is based on skin biopsy though numerous biopsies may be required before the diagnosis can be confirmed



  • The treatment is complex

  • Skin-directed therapies are used initially, including

    • Topical corticosteroids

    • Topical mechlorethamine

    • Bexarotene gel

    • UV phototherapy

  • If the disease progresses, the following may be used:

    • PUVA plus retinoids

    • PUVA plus interferon

    • Extracorporeal photophoresis

    • Bexarotene

    • Histone deacetylase inhibitors (romidepsin or vorinostat)

    • Targeted immunomodulators (brentuximab, mogamulizumab)

    • Total skin electron beam



  • Overly aggressive treatment may lead to complications and premature demise


  • Usually slowly progressive (over decades)

  • Prognosis is better in patients with patch or plaque stage disease and worse in patients with erythroderma, tumors, and lymphadenopathy

  • Survival is not reduced in patients with limited patch disease

  • Elderly patients with limited patch and plaque stage disease commonly die of other causes

When to Refer

  • All patients with suspected or proven diagnosis



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