Topics covered in this Tutorial
Animal Contact lesions, Blisters with red papules, Parapsoriasis, Keratoderma, Raynaud's , Nail and keratoderma syndromes, Purpura, Acnitis, Leptospirosis,
If symmetrical consider dermatitis herpetiformis, vasculitis and dermatitis autoeczematous lesions. If asymmetrical consider pemphigoid, insect bites and scabies.
Atypical Types of Erythema Multiforme
1 Recurrent erythema multiforme
2 A variant with one extending or static lesion
The image below is of dermatitis herpetiformis
This is a term we do not use as much nowadays but the small plaque type of parapsoriasis goes under the name of digitate dermatosis. It is not indurated. It is usually on the trunk. Generally lesions are less than 5cm in diameter and is very well demarcated. With the large plaque parapsoriasis there is some slight induration. There are indistinct irregular borders. It may be scaly and may have so called cigarette paper atrophy. It is particularly seen on the buttocks and the proximal extremities. It is thought that 10% will go on to develop into a frank lymphoma though many people believe that all parapsoriasis represents a lymphoma of sorts. With retiform parapsoriasis or the reticulate variant almost 100% will develop full T cell lymphoma of the skin. In lymphomatoid papulosis about 15% will go on to develop what we know as a frank lymphoma of the skin.
The image below is of a digitate dermatosis
Keratoderma
There obviously are a large number of causes of keratoderma, some are congenital and some are acquired but always look between the toes to exclude a fungus. Remember that you may get crusting rather than keratin with a fungus and also consider crusted scabies where the "keratoderma" is made up of crusts rather than layered keratin. With Darier’s disease you can get pustules and sometimes when you remove the scale in Darier’s disease a little pit is left. With histiocytosis X you get no pustules but sometimes slight skin purpura.
We typically think of it attacking mucosal surfaces but sometimes the process will attack the scalp and present as a scarring alopecia.
The image below is of synechiae in cicatricial pemphigoid
It is usually seen in women under the age of 40. Often all the fingers are involved but gangrene does not happen in Raynaud’s disease. The paroxysmal nature of the process is important. Cold agglutinins, cold haemolysins and cryo precipitins can all cause Raynaud’s but cold fibrinolysins do not. If you have Raynaud’s plus livedo then it is usually due to a cryoprotein. A mnemonic for causes of Raynaud’s disease using the letters of Raynaud’s are –
R for Raynaud’s disease
A for autoimmune such as lupus, scleroderma, dermatomyositis or mixed
connective tissue disease
Y for ‘bloody’ Y – cryos and cold agglutinins
N for neurovascular compression
N for neoplasms
A for arterials such as Buergers disease and arthrosclerosis and arteritis
U for ‘you done it’ – typewriter, piano, vibration, vinyl chloride
D for drugs such as ergot, methysergide, beta blockers, bromocriptine
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| Acrocyanosis rather than Raynaud's. True Raynauds has a white blanching stage. |
The Differentiation of Still’s Disease and Erythema Marginatum
In Still’s disease the rash can come on before the rheumatoid symptoms and it is macular. In erythema marginatum the rash is larger and often annular. Still’s disease starts worse and then gets better.
Ichthyosis and Palmoplantar Keratoderma
Syndromes to consider along with others are tyrosinemia 2 and erythrokeratoderma variabilis.
An AI answer is more informative !
Nails and Palmoplantar Keratoderma Syndromes
Consider hidrotic ectodermal dysplasia, dyskeratosis congenita, pachyonychia congenita and Darier’s disease.
The image below is erythema marginatum seen in Rheumatic fever
Purpura
We usually think of it as either palpable or non-palpable but from an etiological point of view you can think of it as being due to platelet abnormalities or vascular abnormalities. If platelet abnormalities there will be associated ecchymoses and often it is on the upper limbs. If vascular abnormalities it can be physical, toxic, infectious or immune. The physical causes are pressure with a lack of support particularly senile purpura or scurvy, amyloidosis or Ehler’s Danlos syndrome. It can be toxic due to chemicals, drugs and other diseases. It can be due to infection from meningococci or septicaemia. It can be immune with vasculitis, dysproteinemia and lupus and often this causes a painful bruising. In the pigmented purpuric dermatoses, note the Hess test. It is done for five minutes. If you examine an area of 5cm there should be more than five purpuric lesions at 80mm of mercury pressure if positive.
The image below is a pigmented purpuric dermatosis
This is a scar like lesion particularly on the forehead with brownish pigmentation and sometimes some yellow in the middle of it.
Compare granuloma annulare and sarcoidosis. Granuloma annulare is made up of indurated papules. Sarcoid again is papules but they are a different colour. There is fusion of the papules. Both these lesions though will give a crust on the surface when they perforate. Disseminated granuloma annulare can last three to four years. The differential diagnosis is sarcoid, lichen planus and lymphoma. Sometimes it can be annular in other areas such as the back of the hands and it can also be reticulate, but usually disseminated granuloma annulare is papular.
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| Disseminated Granuloma annulare |
Compare lichen scrofulosorum and lichen nitidus. Lichen scrofulosorum usually is quite rough because it has keratosis spinulosa on the surface and feels nutmeg like whereas lichen nitidus is more monomorphic and smooth. Lichen nitidus is acral and genital while lichen scrofulosorum is trunk and buttocks.
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| Lichen scrofulosorum |
This condition due to a spirochete will give jaundice and necrotic lesions in the skin.
The image below is acnitis
