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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.
Still’s disease and Erythema Marginatum
| • | both reticular/annular erythema |
| • | both histologically similar: superficial perivascular infiltrate of neutrophils, and dust, but no fibrin or RBC’s (i.e. no LCV) |
| • | both immune complex diseases (both with symptoms of arthritis) |
| • | memory tool: both associated with disease activity – Still’s 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 |
Still’s 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:
eccrine spiradenoma:
| • | no characteristic distribution |
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
| • | 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
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Xanthoma Disseminatum
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Eruptive Xanthomas
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| • | non-lipidized histiocytes |
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* xanthoma cells = lipidized histiocytes
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