Importance of Symptoms in Dx of Skin Disease: Scabies vs Shingles

A recent case of a couple with scabies

Symptoms first developed towards the end of a holiday in a tropical forest setting

Each had similar symptoms to the other

Principal symptom was pruritus (itching and scratching)

Both cases responded very well to 2 doses of oral ivermectin, 7 days apart

About 3 weeks later, one of the partners re-presented with a rash and reported to staff as scabies that hadn't settled fully

However, the principal symptom was pain, with a mild itchy feel at times

The diagnosis was Herpes zoster (shingles) affecting the Left C6 distribution

This case is due for review in a few days


KEYS TO DIAGNOSIS IN THESE CASES

1. SYMPTOMS
1. SCABIES IS ASSOCIATED WITH INTENSE PRURITUS
2. SHINGLES IS ASSOCIATED WITH SIGNIFICANT PAIN
2. DISTRIBUTION
1. SCABIES HAS A CLASSIC DISTRIBUTION, INCL GROIN, BREASTS, BUTTOCKS, WRISTS & ANKLES
2. HERPES ZOSTER PRESENTS IN A DERMATOME DISTRIBUTION

Importance of Symptoms in Dx of Skin Disease: Scabies vs Shingles

A recent case of a couple with scabies

Symptoms first developed towards the end of a holiday in a tropical forest setting

Each had similar symptoms to the other

Principal symptom was pruritus (itching and scratching)

Both cases responded very well to 2 doses of oral ivermectin, 7 days apart

About 3 weeks later, one of the partners re-presented with a rash and reported to staff as scabies that hadn't settled fully

However, the principal symptom was pain, with a mild itchy feel at times

The diagnosis was Herpes zoster (shingles) affecting the Left C6 distribution

This case is due for review in a few days


KEYS TO DIAGNOSIS IN THIS CASE

1. SYMPTOMS
1. SCABIES IS ASSOCIATED WITH INTENSE PRURITUS
2. SHINGLES IS ASSOCIATED WITH SIGNIFICANT PAIN
2. DISTRIBUTION
1. SCABIES HAS A CLASSIC DISTRIBUTION, INCL GROIN, BREASTS, BUTTOCKS, WRISTS & ANKLES
2. HERPES ZOSTER PRESENTS IN A DERMATOME DISTRIBUTION

Balanitis (glans) + Posthitis (foreskin) - an approach to Mx

If appearance is non-specific (e.g. no visitible warts or other lesions)
And Is not severe -> trial of Rx
--> Hydrozole (OTC) or Hydroform (S4) cream
= 1% hydrocortisone + antifungal (clotrimazole and clioquinol, respectively)

If no improvement after 3 days -> review and ?investigate

Consider primary skin disease, in particular

• psoriasis
• dermatitis (eczema; seborrhoeic dermatitis)
• lichen sclerosis

Consider Ix

• swabs for mcs and HSV PCR
• urine PCR for chlamydia and gonorrhoea
• ?formal STI screen
• including Ix sexual partner/s

?fasting BSL


General Mx for all cases

• foreskin hygiene
• low irritant products for washing and showering

Scabies - Dx and Rx

Pathogenesis
infestation --> immune system sensitised to mite and mite-related products incl eggs
--> symptoms appear

Mite count usually 10-15, but can reach thousands in Norwegian (Crusted) Scabies

Dx
clinical
v itchy
bilateral
wrists, ankles, groin/genitals/buttocks, waist etc
often no burrows to see, especially in warm climate

Rx
2 Rx, one week apart
topical
"Lyclear" (permethrin cream)
OK from 2 months old but must be > 15 kg
Head-to-toe at bedtime. Wash off in the morning.
oral
ivermectin ("Stromectol")
150-200 mcg per kg
100kg = 15 - 20 mg
=> 5 or 7 tablets (each 3mg)
"Ready-reckoner" -  adults 15 mg; children 6 mg

Hot wash bed linen, towels, clothing
Rx family and close contacts
(significant incidence of asymptomatic cases => carriers)

Pets don't harbour human mites
=> can't give you scabies; no need to Rx

Response to Rx usually within 3 days (most resolved in 2 weeks), 
but pruritus can remain for up to 2 months

Dx Tinea (corporis) vs Granuloma Annulare

Tinea => border is scaly


Granuloma Annulare => border is non-scaly

Dx Acne Vulgaris vs Acne Rosacea

Vulgaris => comedones (keratin plugs in pilosebaceous unit) - white or black (if oxidised)


Rosacea => no comedones


NB:
Important DDx of (white heads) comedones = Milia  |  Usually found in infra-orbital/cheek regions

Milia = keratin "bleb" vs keratin "plug" in vulgaris (forming a comedone)

Parapsoriasis - What Is It?

A continuum is thought to exist: 

Chronic dermatitis ---> Parapsoriasis ---> T cell lymphoma (mycosis fungoides)

Parapsoriasis may be defined thus

1. Plaque-type (usually elderly and on legs; circinate patches may be red, yellow, brown, pink; plaques tend to be thin)

    (sometimes called chronic scaly superficial dermatitis)

.. Small plaque

.. Large plaque

2. Lichenoid

.. Pityriasis lichenoides

.... acute

.... chronic

Most cases aren't painful or itchy

If this is part of DDx -> consider punch biopsies to exclude a T cell lymphoma

Else histology changes tend to be non-specific

Emollients very important to hydrate skin

Otherwise,Rx tends to be that for dermatitis, including topical c.steroids and UV therapy

Always a good reference site, I find ...

Parapsoriasis - Medscape Reference

emedicine.medscape.com/article/1107425-overviewApr 19, 2013 - Parapsoriasis describes a group of cutaneous diseases that can be characterized by scaly patches or slightly elevated papules


DDx includes
- dermatitis (particularly circinate/nummular type)
- psoriasis (plaque or guttate form)
- T cell lymphoma (mycosis fungoides)
- Pityriasis rosea
- Syphylis (secondary)

--> biopsies

--> ?syphylis serology