Polycythaemia rubra vera
• Itching or paraesthesiae, typically after a hot shower or bath.
• Erythromelalgia: attacks of burning pain in legs, often worse in bed, when the patient is
unable to tolerate heat under bedclothes. Skin is erythematous but cool, and the legs may
be swollen. Raised platelets. Aspirin is helpful. Resolves when polycythaemia controlled.
Essential thrombocythaemia
• Livedo reticularis and/or retiform purpura with painful leg ulcers secondary to
vasculopathy.
• Erythromelalgia.
Leukaemias and lymphomas
• Neutrophilic dermatoses: Sweet syndrome and pyoderma gangrenosum.
• Interstitial granulomatous dermatitis.
• Cutaneous lymphoma, Sézary syndrome, and leukaemia cutis.
• Adverse reactions in skin and nails secondary to chemotherapy.
• Paraneoplastic pemphigus (rare). Seen most often in chronic lymphocytic lymphoma,
non-Hodgkin lymphoma, or Castleman disease (a rare lymphoproliferative disorder).
Alemtuzumab may be helpful.
Rosai–Dorfman disease (sinus histiocytosis with massive lymphadenopathy)
• Presents with prominent painless cervical lymphadenopathy in ~90% of cases. Tends to
affect children and young adults.
• Associated with fever, raised WCC and ESR, polyclonal hypergammaglobulinaemia,
RBC autoantibodies, juvenile-onset diabetes, and asthma.
• Extranodal disease occurs in around 40% patients.
• Skin is the most commonly affected site—single or multiple, yellow, erythematous, or
brown papules, nodules, or plaques commonly affecting the torso, followed by the head
and neck.
• Usually runs a benign, self-limiting course.
• Rarely exists as purely the cutaneous Rosai–Dorfman disease (RDD) form (older
women); no reported risk of developing systemic disease.
• Lesions can spontaneously resolve or persist, with variable response to therapy.
• Treatment options include surgical excision, topical or intralesional steroids,
cryotherapy, or radiotherapy.
Hyperglobulinaemic purpura
Asymptomatic diffuse petechiae and purpuric macules at sites of pressure, minor trauma,
or stasis. Purpura may be precipitated by exercise. Occasionally, paraesthesiae precede
the rash. Occurs in association with chronic inflammatory diseases, including:
• LE, RA, and Sjögren syndrome.
• Sarcoidosis.
• Chronic hepatitis.
• Inflammatory bowel disease.
• Chronic infections.