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Cousins

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Some diseases can be thought of as "cousins";  they are related but different in at least a few distinct ways.  Learning these diseases together can be useful because examining there similarities and differences side by side helps put each disease into a conceptual context in your mind.

 

Stills disease and Erythema Marginatum

both evanescent (hours)
both reticular/annular erythema
both histologically similar:  superficial perivascular infiltrate of neutrophils, and dust, but no fibrin or RBCs (i.e. no LCV)
both immune complex diseases  (both with symptoms of arthritis)
memory tool:  both associated with disease activity Stills appears in the evening with the high fevers;  e. marginatum is associated with active carditis

 

Erythema Marginatum:

associated with active carditis
one of 5 major Jones criteria for Rheumatic Fever:  subcutaneous nodules, Sydenhams chorea, carditis, polyarthritis

 

Stills disease:

rash appears in evening with high temperature
dermal edema with dilated vessels

 

 

Cylindroma and Eccrine Spiradenoma

both composed of lobules surrounded by hyaline sheath (though more striking in cylindroma)
both composed of two types of tumor cells
small basophilic cells arranged along periphery of the tumor lobules
larger, paler cells in the center of the islands
both belong to the least mature group of appendage tumors
eccrine spiradenoma direction of differentiation is toward both ductal and secretory segments of eccrine sweat glands
cylindroma a very immature sweat gland epithelioma, partially eccrine and partially apocrine in differentiation

 

cylindroma:

jigsaw puzzle
scalp or face

 

eccrine spiradenoma:

blue balls
no characteristic distribution
painful tumor ddx

 

 

 

Epidermolysis Bullosa Acquisita and Bullous SLE

has the following in common with EBA:
antibodies recognize EBA antigen (type VII collagen)
the split occurs in the sublamina densa zone
indirect immunofluorescence  may be positive in intact or separated skin
presence of HLA-DR2 is markedly increased in both conditions

 

bullous LE distinctive features include:
a diagnosis of SLE by criteria of the ARA
a widespread, non-scarring vesicobullous eruption
(skin fragility, scarring, and milia are not features)
often begins in second or third decade (EBA in fourth or fifth)
histology characteristically like that of dermatitis herpetiformis (rare in EBA)
remitting and often resolves in less than a year (EBA often lasts many years)
most patients respond dramatically to dapsone (EBA patients do not predictably respond to any treatment)

 

 

Eruptive vellus hair cysts vs. Steatocystoma multiplex

clinically similar
both can be autosomal dominant
steatocystoma cysts may contain one or more lanugo hairs
hybrid cysts with features of both are sometimes seen

 

 

 

 

Generalized Eruptive Histiocytoma

ßà

Xanthoma Disseminatum

ßà

Eruptive Xanthomas

non-lipidized histiocytes

 

xanthoma cells*

 

xanthoma cells*

 

 

Touton giant cells

 

Touton giant cells

 

 

normal serum lipids

 

increased triglycerides

* xanthoma cells = lipidized histiocytes