Endless Itch

Question 1

What questions do you want to ask about itching?

Answer 1

• Which came first: the itching or rash? - if itching is first it is more likely to be systemic, neuropathic or psychogenic cause rather than a dermatology one
• Detailed history including timing and distribution of itch
• Is it in specific areas or all over?
• Clear drug history for any potential causes e.g. opiates
• SH including smoking, alcohol, occupation
• Focused system enquiry
• Fever - foreign travel

Question 2

What is the different between pruritis and prurigo?

Answer 2

Pruritis: itching without a rash
Prurigo: intensely itchy papules and nodules

Question 3

What is chronic pruritis?

Answer 3

Itching lasting >6 weeks, can lead to characteristic secondary skin lesions including excoriations, lichenification and hyperpigmentation (or hypopigmentation in darker skin). Can have erosions and linear scarring (pale white areas) due to excoriation (scratching).

Question 4

What systems review do you want to cover for itching?

Answer 4

• Nails and hair: e.g. clubbing, splinter haemorrhages, palmar erythema, nail fold telangiectasia, loss of hair or hirsutism
• GI system: hepatomegaly, splenomegaly, abdominal masses
• CV: murmurs
• Respiratory: abnormal breath sounds
• Haematological: lymphadenopathy
• Neurological: limb weakness, facial asymmetry, cognition

Question 5

What investigations do you do for itch?

Answer 5

• FBC, ESR, TFTs, U+Es
• Serum immunoglobulins and electrophoresis
• Random glucose
• HIV serology
• CXR

Question 6

What are non-skin causes for widespread itch?

Answer 6

• Malignancy: Hodgkin’s lymphoma (paraneoplastic pruritis); myeloid and lymphatic leukaemia; solid malignant tumours (paraneoplastic manifestation)
• Haematological: polycythaemia rubra vera; myeloid dysplasia
• Inflammatory: dermatomyositis; scleroderma
• Infectious/infestations: HIV, Hep C
• Neurological: peripheral neuropathy, post-herpetic neuropathy (complication of shingles), MS
• Psychogenic: parasitophobia, OCD, depression/anxiety
• Metabolic: hyperthyroidism, CKD (secondary hyperparathyroidism, uremic pruritis), pancreas/adrenals (leads to diabetes)
• GI: cholestasis (hyperbilirubinaemia), pancreas tumour
• Drugs

Question 7

What are differentials for itch?

Answer 7

• Diabetes - often presents with cutaneous fungal infections
• Tuberous sclerosis complex: mutations in TSC1 and TSC2 gene. These provide instructions to make hamartin and tuberin proteins which help regulate growth and size > tumour suppressors.
• Sarcoidosis: red/brown firm nodules around mouth and nose, bilateral hilar lymphadenopathy
• Pyoderma gangrenosum: can be caused by underling haematological malignancies and inflammatory conditions such as IBD and RA, ulcer with violaceous (purple) undermined edges
• Gastric cancer (also obesity, DM, Cushing’s, PCOS) causes Acanthosis Nigricans (darkened, thickened patches of skin in armpit and around groin and neck
• Peri-orbital xanthalasma - hypercholesteraemia
• DM: diabetic foot ulcers, palmar xanthomata (uncontrolled diabetes), necrobiosis lipoidica
• Erythema nodosum
• Purpuric papules
• VZV reactivation