It is not surprising that the skin is involved in many systemic diseases – it would be odd if it wasn’t. Knowing about these clues to systemic disease is satisfying and gives you (‘Sherlock Holmes’) the chance of astonishing your colleagues with an accurate diagnosis on apparently little information.

Conditions with Several Causes

Erythema Nodosum (Figure 41.2)

Ill-defined tender raised red lesions, several centimetres across, on the shins.

• Tuberculosis
  
• Sarcoidosis
  
• Beta-haemolytic Streptococcus – upper respiratory tract infection
  
• Drugs (e.g. oral contraceptive pill, sulphonamides)
  
• Autoimmune disease (e.g. systemic lupus erythematosus)
  
• Inflammatory bowel disease, especially Crohn’s disease.

Pruritus (Note Correct Spelling)

Generalised itchiness. First rule out skin causes of pruritus such as early pemphigoid, dermatitis herpetiformis or scabies.

• Hyperthyoidism
  
• Lymphoma (e.g. Hodgkin’s disease)
  
• Renal failure
  
• Hepatobiliary disease, including cholestasis, primary biliary cirrhosis
  
• Iron deficiency
  
• Polycythemia rubra vera. Pruritus provoked by water contact (e.g. having a shower)
  
• HIV infection.

Purpura (Figure 41.3)

Red or dark blue areas, usually flat. Do not blanche on pressure because the red blood cells have come out of the blood vessels and are in the dermis.

• Low platelets (thrombocytopenia)
  
• Drugs (e.g. warfarin)
  
• Scurvy (vitamin C deficiency)
  
• Amyloidosis
  
• Henoch–Schönlein purpura
  
• Infections (e.g. meningococcal meningitis).

Pyoderma Gangrenosum (Figure 41.4)

Persistent ulceration with purple undermined edge.

• Ulcerative colitis, Crohn’s disease
  
• Rheumatoid arthritis
  
• Myeloproliferative disease (e.g. acute lymphoblastic leukaemia, chronic myeloid leukaemia, myelodysplasia, paraproteinaemia)
  
• Systemic malignancy.

Erythema Multiforme (Figure 41.5)

Many red (‘erythema’) lesions over body and limbs. May be target-like but can be many shapes (‘multiforme’).

• Viral disease, especially herpes simplex
  
• Mycoplasma infection
  
• Drugs (e.g. sulphonamides), but many implicated.

Depending on the cause, withdraw drug or treat infection and provide urgent inpatient supportive therapy.

Acanthosis Nigricans (Figure 41.6)

Dark velvety thickening in flexures, especially axillae, groin.

• Diabetes
  
• Insulin resistance and obesity
  
• Gastric adenocarcinoma.

Related posts:

Surgical basics Atopic dermatitis Fungal infections Urticaria Skin breakdown Autoimmune disease and vasculitis

Stay updated, free articles. Join our Telegram channel

Join