Lists, Common Differential Diagnoses, and Mnemonics




(1)
Department of Dermatology, University of Pennsylvania, Penn Presbyterian Medical Center Medical Arts Building, Philadelphia, PA, USA

 



15.1 Differentials

15.1.1 Triads and Near Triads

15.1.2 Important Clinical Differentials

15.1.3 Differentials by Distribution/Anatomic Location

15.1.4 Differentials by Morphology and Configuration

15.1.5 Other Clinical Differentials

15.1.6 Other Disease Category Differentials

15.2 Associations and Work-Ups

15.2.1 Disease-Specific Associations

15.2.2 Work-Ups

15.3 Acronyms

15.3.1 List of Acronyms

15.3.2 Diseases Known Primarily by Acronyms

15.4 Dermatopathology

15.4.1 Differentials, Lists, and Mnemonics

15.4.2 Lists and Notes

15.4.3 Other Factoids

15.4.4 Stains and Immunohistochemistry

15.5 Lists

15.5.1 Quick Quiz Lists

15.5.2 Often Asked Facts

15.5.3 Interesting Factoids

15.5.4 Nevi, Erythemas, and Other Common Terms

15.5.5 Clinical Signs (with Nicknames or Eponymous Names)

15.5.6 Nail and Teeth Findings

15.6 Commonly Confused Diseases

15.6.1 Sound-Alikes and Look-Alikes

15.6.2 Other Similar Sounding Diseases

15.6.3 Misnomers

15.7 Other Lists

15.7.1 Types of Certain Dermatologic Diseases

15.7.2 Drug Eruption Mnemomics

15.7.3 Other Lists


Abstract

This chapter contains different groupings and listings of diseases and findings for the purposes of better learning and memorization. Hopefully these differentials, lists, and mnemonics are helpful to you!


Keywords
ListsDifferentialsAcronymsMnemonics



15.1 Differentials



15.1.1 Triads and Near Triads


Triads are useful ways to remember common differential diagnoses for specific presentations. They are not meant to be complete, but rather to assist with quick recall of top possibilities. The mind has trouble recalling more than three or four options, so these help distill certain differentials for better memory.

FLESHY EXOPHYTIC PAPULE



  • Acrochordon


  • Intradermal nevus


  • Neurofibroma


SOLITARY NODULE IN A CHILD



  • Spitz nevus


  • JXG


  • Mastocytoma


SUPERFICIAL PUSTULES



  • Candidiasis


  • Pustular psoriasis


  • AGEP


MOST COMMON KOEBNERIZING DISEASES



  • Psoriasis


  • Lichen planus


  • Lichen nitidus


RETICULATED ERYTHEMA



  • Parvovirus (Fifth’s disease aka erythema infectiosum)


  • Erythema marginatum (rheumatic fever)


  • Still’s disease

Also, erythema ab igne (more brown/violaceous)

SALT AND PEPPER PATCH DDX



  • Follicular repigmentation in vitiligo


  • Scleroderma salt and pepper confetti patches


  • Leopard skin in onchocerciasis


TRACHYONYCHIA (20 nail dystrophy)



  • Lichen planus


  • Psoriasis


  • Alopecia areata


CYSTIC PAPULES ON TEENAGER’S CHEST



  • Acne


  • Eruptive vellus hair cysts


  • Steatocystoma multiplex


FACIAL RASH IN A NEONATE



  • Seborrheic dermatitis


  • Atopic dermatitis


  • Neonatal lupus


  • Less likely:


  • Psoriasis


  • Langerhans cell histiocytosis


HELIOTROPE RASH DDX



  • Dermatomyositis


  • Contact dermatitis (think volatiles like nail polish on eyelids)


  • Trichinosis


CAUSES OF MACROGLOSSIA



  • Mnemonic = AAA


  • Amyloidosis


  • Angioedema


  • Acromegaly


YELLOW WAXY PERIORBITAL PAPULES



  • Syringomas


  • NXG


  • Amyloidosis


  • Xanthelasma


  • Also, consider sarcoidosis


DERMAL PAPULES IN A TATTOO



  • Allergic reaction to tattoo dye


  • Sarcoidosis


  • Keloids/scarring


  • Atypical mycobacterial infection


MIDLINE FACIAL NODULE IN CHILD



  • Dermoid cyst


  • Encephalocele


  • Nasal glioma


  • Also, hemangioma


SOLITARY SCALP PLAQUE IN NEONATE



  • Aplasia cutis congenita


  • Nevus sebaceus


MARFANOID CLINICAL APPEARANCE



  • Marfan syndrome


  • Homocystinuria


  • MEN-IIb


TUBEROUS SCLEROSIS APPEARANCE



  • Tuberous sclerosis


  • MEN-I


MULTIPLE ANGIOFIBROMAS



  • Tuberous sclerosis


  • MEN-I


  • These are only in case reports:


  • Cowden’s disease


  • Birt-Hogg-Dubé


15.1.2 Important Clinical Differentials




PAINFUL TUMORS



  • Mnemonic = BLEND AN EGG



    • Blue rubber bleb nevus syndrome


    • Leiomyoma


    • Eccrine spiradenoma


    • Neuroma


    • Dermatofibroma, Dercum’s disease (multiple painful lipomas)


    • Angiolipoma


    • Neurilemmoma


    • Endometrioma


    • Glomus tumor


    • Granular cell tumor


ERYTHRODERMA



  • Mnemonic = pretty please don’t make beets, dear



    • Psoriasis


    • Pityriasis rubra pilaris (PRP)


    • Dermatitis (Atopic, Contact, Seborrheic, Stasis)


    • Mycosis fungoides/CTCL


    • Blistering (Pemphigus foliaceus, BP)


    • Drug eruption


    • Other – lichen planus, Norwegian scabies, GVHD, rarely sarcoid, paraneoplastic


    • In infants: don’t forget SSSS, ichthyoses


FLESH-COLORED PAPULES ON THE FACE DDX



  • Melanocytic nevi


  • Syringomas


  • Xanthomas/xanthelasma


  • Apocrine and eccrine hidrocystomas


  • Trichoepitheliomas


  • Sebaceous hyperplasia


  • Angiofibromas


  • Lipoid proteinosis


  • Colloid milia


  • Favre–Racouchot syndrome = nodular elastosis with cysts and comedones


  • Tricholemmomas

Also (less flesh-colored): molluscum, plane warts, DPN

“PURPLE PLUMS”



  • Can be pink/purple cherry-like to plum-like soft to firm dermal nodules



    • Leukemia cutis/lymphoma


    • Metastatic cancer


    • Kaposi’s sarcoma (and bacillary angiomatosis)


    • Merkel cell carcinoma


    • Angiosarcoma


    • Amelanotic melanoma


    • Dermatofibrosarcoma protuberans (DFSP)


    • Soft tissue sarcoma/Leiomyosarcoma


    • Plasmacytoma


BLUEBERRY MUFFIN BABY DDX



  • Mnemonic = HI Blueberry Muffin



    • Hemolysis (spherocytosis, ABO incompatibility) – extramedullary hematopoeisis


    • Infection (TORCHES) – extramedullary hematopoeisis


    • Benign (multiple hemangiomas)


    • Malignancy (neuroblastoma most common, leukemia)


SPOROTRICHOID SPREAD



  • Mnemonic = CAT N SPLAT



    • Cat scratch disease


    • Atypical mycobacteria (esp. M. marinum)


    • Tuberculosis


    • Nocardia


    • Sporotrichosis


    • Phaeohyphomycosis


    • Leishmaniasis


    • Anthrax


    • Tularemia

Note: most common = sporotrichosis and atypical mycobacteria

RETIFORM PURPURA



  • ANCA-associated vasculitides (Wegener’s, MPA, PAN, Churg-Strauss)


  • Antiphospholipid antibody syndrome


  • Calciphylaxis


  • Cocaine/levamisole-associated vasculopathy


  • Cryoglobulinemia


  • Disseminated intravascular coagulopathy (DIC)/Purpura fulminansHeparin-induced thrombocytopenia (HIT)


  • Septic vasculitis


  • Warfarin skin necrosis


  • Cholesterol emboli


  • Oxalosis


LEONINE FACIES



  • MF/CTCL


  • Leprosy (lepromatous)


  • Actinic reticuloid


  • Scleromyxedema


  • Paget’s disease of bone


  • Amyloidosis


  • Acromegaly


  • Sarcoidosis


  • Leishmaniasis


  • Multicentric reticulohistiocytosis


VEGETATING/GRANULATING/ULCERATING PLAQUE DDX



  • Tuberculosis (primary inoculation or tuberculosis verrucosa cutis)


  • Atypical mycobacterial infection


  • Deep fungal infection (chromomycosis, blastomycosis)


  • Leishmaniasis


  • Mycetoma (Actinomyces/Nocardia)


  • Neoplasms (SCC, sarcomas, metastatic)


  • Pyoderma gangrenosum


  • Gummas (syphilis, TB)


  • Halogenoderma (from bromides, iodides)


PALMAR PITTING DDX



  • Palmar pits (BCC Nevus syndrome)


  • Punctate palmoplantar keratoderma (PPPK)/keratosis punctata palmaris et plantaris


  • Punctate porokeratosis


  • Punctate keratoses (of palmar creases)


  • Arsenical keratoses


  • Pitted keratolysis (Corynebacterium)


  • Keratolysis exfoliativa (more annular collarettes of scale on palms)


CUTANEOUS HORN DDX



  • Mnemonic = SAWS



    • Seborrheic keratosis


    • Actinic keratosis


    • Wart (Verruca vulgaris)


    • Squamous cell carcinoma (including keratoacanthoma and SCCIS)


15.1.3 Differentials by Distribution/Anatomic Location




THE SHINS



  • Stasis dermatitis


  • Asteatotic eczema/eczema craquele


  • Pyoderma gangrenosum


  • Leukocytoclastic vasculitis


  • Pigmented purpuric dermatosis (Schamberg’s)


  • Necrobiosis lipoidica


  • Pretibial myxedema


  • Erythema nodosum


  • Diabetic dermopathy (shin spots)


  • Lichen amyloidosus


  • Hypertrophic lichen planus


  • Lipodermatosclerosis


  • Disseminated superficial actinic porokeratosis (DSAP)


  • Ichthyosiform sarcoid


  • Pseudo-Kaposi’s sarcoma (acroangiodermatitis)


  • Pancreatic panniculitis


ELBOWS AND KNEES



  • Psoriasis


  • Dermatomyositis


  • Dermatitis herpetiformis


  • Xanthomas


  • Rheumatoid nodules


  • Papular urticaria


INTERTIGINOUS AREAS (AXILLAE/INGUINAL FOLDS)



  • Intertrigo: candidiasis, irritant dermatitis seborrheic dermatitis, inverse psoriasis, erythrasma, contact dermatitis, inverse pityriasis rosea


  • Hidradenitis suppurativa


  • Axillary granular parakeratosis


  • Pemphigus vegetans


  • Hailey-Hailey disease


HANDS AND FEET



  • Hand, foot, and mouth disease (Coxsackie)


  • Dyshidrotic eczema/hand dermatitis


  • Secondary syphilis (classic palms/soles)


  • Psoriasis/Palmoplantar pustulosis


  • Erythema multiforme


  • Tinea manuum and tinea pedis (“one hand, two feet” syndrome)


  • Vitiligo


  • Warts


  • Palmoplantar keratoderma (non-psoriasis types including PRP)


  • Acral erythema of chemotherapy (hand-foot syndrome or erythrodysesthesia)


  • Raynaud’s phenomenon


  • Perniosis/Chillblains


  • Palmoplantar hyperhidrosis


  • Vasculitis/vasculopathy (embolic disease, endocarditis, cryoglobulinemia)


  • Papular purpuric gloves and socks syndrome (Parvovirus)


EROSIONS/BLISTERS ON DORSAL HANDS DDX



  • Acute contact dermatitis (poison ivy)


  • Porphyria cutanea tarda


  • Pseudoporphyria


  • Epidermolysis bullosa acquisita


  • Bullous lupus


  • Epidermolysis bullosa simplex


THE EARS



  • Keloids


  • Ear pit


  • Accessory tragus


  • Seborrheic otitis


  • Discoid lupus


  • Otitis externa


  • Cocaine/levamisole-associated vasculopathy


  • Relapsing polychondritis


  • Leprosy


  • Lupus vulgaris (tuberculosis)


  • Lupus pernio (sarcoidosis)


  • Pseudocyst of the auricle


  • Chondrodermatitis nodularis helicis


  • Angiolymphoid hyperplasia with eosinophilia (ALHE) and Kimura’s disease


  • Venous lake


  • Non-melanoma skin cancers, actinic keratosis, atypical fibroxanthoma


CHRONIC DISEASE OF THE NOSE



  • Tuberculosis (lupus vulgaris)


  • Leprosy


  • Syphilis


  • Leishmaniasis


  • Rhinoscleroma


  • Sarcoidosis


  • Granulomatosis with polyangitis (Wegener’s)


  • Basal cell carcinoma


THE LIPS



  • Angular cheilitis


  • Actinic cheilitis


  • Cheilitis granulomatosis


  • Cheilitis glandularis


  • Herpes labialis


  • Venous lake


  • Labial lentigo


  • Pyogenic granuloma


  • Angioedema


  • Stevens-Johnson syndrome


  • Erythema multiforme


  • Paraneoplastic pemphigus


  • Microcystic adnexal carcinoma


  • SCC


  • Fordyce spots


  • Perioral dermatitis


  • Lip licker’s dermatitis


  • Mucocele


  • Condyloma acuminata


WHITE PLAQUE ON ORAL MUCOSA



  • Lichen planus


  • Thrush


  • Leukoplakia (SCCIS)


  • Oral hairy leukoplakia (EBV)


  • White sponge nevus


  • Leukokeratosis associated with pachyonychia congenita (type 1 >2, not premalignant)


  • Leukoplakia associated with dyskeratosis congenita (premalignant)


  • Darier’s


  • Aspirin burn


  • HPV: Oral florid papillomatosis, Heck’s disease


  • Verrucous xanthoma


  • Nicotinic stomatitis = fissures/thickened white/red cobblestone papules on hard > soft palate


CAUSES OF GINGIVAL HYPERPLASIA



  • Drugs – phenytoin, calcium channel blockers, cyclosporine


  • Diseases – AML, sarcoidosis, granulomatosis with polyangitis (Wegener’s), scurvy, pregnancy


THE TONGUE



  • Geographic tongue (annulus migrans, benign migratory glossitis) – can see similar in pustular psoriasis


  • Fissured tongue (lingua plicata, scrotal tongue)- see in Melkersson-Rosenthal syndrome (fissured tongue, Bell’s palsy, and lip swelling – non-caseating granulomatous inflammation), Down syndrome


  • Black hairy tongue – may be related to poor hygiene, smoking


  • Granular cell tumor – tongue is common location


GENITAL LESIONS



  • Painful: HSV, Chanchroid


  • Painless: LGV, Granuloma Inguinale (Donovanosis), Syphilis (primary chancre, secondary condyloma lata)


RED PLAQUE ON PENIS



  • Candidiasis


  • Psoriasis


  • Lichen planus


  • Fixed drug eruption (especially from tetracyclines)


  • Irritant balanitis


  • Zoon’s balanitis


PENILE/SCROTAL PAPULES



  • Condyloma acuminata


  • Pearly penile papules (angiofibromas)


  • Comedones/folliculitis


  • Normal hair follicles


  • Tyson glands (ectopic sebaceous glands)


  • Lichen planus


  • Psoriasis


  • Non-venereal sclerosing lymphangitis of the penis


  • Condyloma lata (secondary syphilis)


  • Angiokeratomas


  • Acrochordons and nevi


  • Idiopathic scrotal calcinosis


NECK FULLNESS DDX



  • Goiter


  • Madelung disease (benign symmetric lipomatosis)


  • Rosai-Dorfman disease (sinus histiocytosis with massive LAD)


  • Lymphoma (Hodgkin’s and non-Hodgkin’s)


  • Scrofula


NAIL TUMORS



  • Glomus tumor


  • Digital myxoid cyst


  • Periungual fibromas (Koenen tumors, in tuberous sclerosis)


  • Nail matrix nevus


  • Onychomatricoma


  • SCC


  • Melanoma


LONGITUDINAL MELANONYCHIA



  • Racial predisposition


  • Trauma


  • Medication reaction


  • Pregnancy


  • Addison disease


  • Peutz-Jeghers syndrome


  • Laugier-Hunziker syndrome


  • SCCIS


  • Onychomycosis


  • Benign nail matrix nevi


  • Melanoma


15.1.4 Differentials by Morphology and Configuration




PUSTULES



  • Acne


  • Superficial folliculitis


  • Pustular psoriasis


  • Palmoplantar pustulosis


  • Acute generalized exanthematous pustulosis (AGEP)/pustular drug eruptions


  • Subcorneal pustular dermatosis (Sneddon-Wilkinson disease)


  • Infantile acropustulosis


  • Candiasis


  • Tinea


  • Dyshidrotic eczema


  • Impetigo


  • Varicella/HSV


  • Erosive pustular dermatosis of the scalp


ANNULAR LESIONS

1.

Vascular



  • Urticarial (<24 h) = urticaria, erythema marginatum


  • Urticarial, but >24 h = urticarial vasculitis, erythema multiforme, figurate erythemas (EAC, erythema migrans/Lyme, erythema gyratum repens), exanthemaotus drug eruptions, urticarial syndromes (Muckle-Wells, FMF), erythrokeratoderma variabilis


  • Purpuric = urticarial vasculitis, purpura annularis telangiectoides (BPP), acute hemorrhagic edema of infancy


  • Serpiginous (larva currens, cutaneous larva migrans)

 

2.

Papulosquamous (Do a KOH!)



  • Psoriasiform = psoriasis, CTCL, even seb derm


  • Pityriasiform = tinea, secondary syphilis, pityriasis rosea


  • Lichenoid = lichen planus

 

3.

Dermal



  • Granulomatous = granuloma annulare, sarcoid, leprosy


  • Lymphocytic = connective tissue disease (SCLE, tumid lupus, Still’s disease, Sjögren’s), Jessner’s


  • Other: Sweet’s, Well’s syndrome

 

4.

Vesiculobullous



  • Pustular (subcorneal) = pustular psoriasis, Sneddon-Wilkinson, IgA pemphigus


  • Bullous (subepidermal) = urticarial BP, linear IgA

    Rare = perforating (elastosis perforans serpiginosa)

 


CATEGORIES OF LINEAR DISEASES



  • Blaschkoid/nevoid (mosaicism)


  • Dermatomal


  • Autoinnoculation


  • Lymphatic/sporotrichoid


  • “Outside jobs” = contact dermatitis, Koebnerized


  • Phlebitis


LINEAR ENTITIES



  • Lichen striatus (in kids)


  • Blaschkitis (in adults)


  • Linear lichen planus


  • Linear Darier’s


  • Linear porokeratosis


  • Inflammatory linear verrucous epidermal nevus (ILVEN)


  • Outside jobs: Koebnerized diseases (LP, lichen nitidus, psoriasis), contact dermatitis


LINEAR BULLAE DDX



  • Epidermolysis bullosa (mechanobullous disease)


  • Acute contact dermatitis (outside job)


15.1.5 Other Clinical Differentials




CAUSES OF ERUPTIVE KERATOACANTHOMAS



  • Grzybowki syndrome


  • Ferguson-Smith syndrome


  • Muir-Torre syndrome (not really eruptive)


  • BRAF inhibitor medications


CAFÉ AU LAIT MACULES



  • Coast of California (regular borders): NF


  • Coast of Maine (irregular borders): McCune Albright syndrome


CAUSES OF FOLLICULAR ATROPHODERMA



  • Keratosis pilaris atrophicans (ulerythema ophyrogenes)


  • Conradi-Hunermann


  • Bazex syndrome (BCCs with follicular atrophoderma)


  • Rombo syndrome (BCCs with atrophoderma vermiculatum)


DISCOLORED HAIR



  • Green hair = from copper chelation


  • Yellow hair = from selenium sulfide


15.1.6 Other Disease Category Differentials




HYPERSENSITIVITY REACTIONS



  • Type 1: IgE mediated; e.g. urticaria, anaphylaxis


  • Type 2: cytoxic; antibody-dependent (IgM or IgG); e.g. hemolytic anemia


  • Type 3: antigen-antibody immune complex; e.g. serum sickness, vasculitis


  • Type 4: delayed-type hypersensitivity; (T-cells) allergic contact dermatitis


BREAST CANCER SKIN MANIFESTATIONS

1.

Peau d’orange (can see with any infiltrative disease)

 

2.

Carcinoma erysipeloides (inflammatory breast cancer)

 

3.

Carcinoma en cuirasse (et satellite nodules de Valpeau)

 

4.

Alopecia neoplastica

 

5.

Carcinoma telangiectoides

 

6.

Paget’s disease (from direct extension of ductal carcinoma – must involve nipple)

 


SPIROCHETES



  • Mnemonic = rat biting into a BLT



    • Rat-bite fever (Spirillium minus, Streptobacillus moniliformis)


    • Borrelia


    • Leptospirosis


    • Treponemes


DIMORPHIC FUNGI



  • Sporotrichosis


  • Histoplasmosis


  • Blastomycosis


  • Coccidiodomycosis


  • Paracoccidiodomycosis


ANGIOINVASIVE ORGANISMS



  • Mucor


  • Rhizopus


  • Pseudomonas (ecthyma gangrenosum)


  • Aspergillus


  • Fusarium


CHILDHOOD VIRAL EXANTHEMS



  • First Disease – Rubeola/Measles – Paramyxovirus


  • Second Disease – Scarlet Fever – Streptococcus (not viral)


  • Third Disease – Rubella – Togavirus


  • Fourth Disease – Duke’s Disease – not specific


  • Fifth Disease – Erythema infectiosum – Parvovirus B19


  • Sixth Disease – Roseola/Exanthem subitum – HHV-6/7


HUMAN HERPES VIRUSES



  • HHV-1 = HSV-1, herpes simplex virus-1


  • HHV-2 = HSV-2, herpes simplex virus-2


  • HHV-3 = VZV, varicella zoster virus


  • HHV-4 = EBV, Epstein-Barr virus


  • HHV-5 = CMV, cytomegalovirus


  • HHV-6 = possibly related to pityriasis rosea and roseola, DRESS


  • HHV-7 = possibly related to pityriasis rosea and roseola, DRESS


  • HHV-8 = related to Kaposi’s sarcoma, Castleman’s disease, primary effusion lymphoma

Note:



  • Alpha – HHV-1,2,3 (herpes ones)


  • Beta = HHV-5,6,7 (CMV, roseola)


  • Gamma = HHV-4 and 8 (oncogenic ones)


INSECTS

1.

Arthopods (6 legged)



  • Fleas, flies, mosquitoes, bed bugs

 

2.

Arachnids (8 legged): four categories



  • Ticks


  • Spiders


  • Scorpions


  • Mites

 


TINEA CAPITIS FLUORESCENCE



  • Ectothrix: “Cats and Dogs Fight & Growl Sometimes”:



    • M. canis, M. audouinii, M. distortum, M. ferrugineum, some M. gypseum, T. schoenleinii


  • →Nonfluorescent ectothrix = T. mentag, T. rubrum, T. verrucosum, T. megninii, M. gypseum. M. nanum


  • Endothrix: “Ringo gave Yoko Two Squeaky Violins”



    • T. rubrum, T. gourvilli, T. yaounde, T. tonsurans, T. schoenleinii, T. soundanese, T. violaceum


ATYPICAL MYCOBACTERIA GROUPS (Runyon criteria)



  • Group 1 – Photochromogens (e.g. Mycobacterium kansasii, Mycobacterium marinum, Mycobacterium simiae) = make pigment with light


  • Group 2 – Scotochromogens (e.g. Mycobacterium scrofulaceum, Mycobacterium szulgai, Mycobacterium gordonae) = make pigment without light


  • Group 3 – Nonphotochromogens (e.g. Mycobacterium malmoense, Mycobacterium xenopi, Mycobacterium avium-intracellulare) = no pigment


  • Group 4 – Fast growers (3–5 days) (e.g. Mycobacterium fortuitum, Mycobacterium abscessus, Mycobacterium chelonae)



    • Mnemonic = “fast as a cheetah”


DISEASES WITH BODY LICE AS A VECTOR



  • Body lice = Pediculus humanus var. corporis


  • Mnemonic = BRB



    • Louse-borne epidemic typhus (Rickettsia prowazekii)


    • Relapsing fever (Borrelia recurrentis)


    • Trench fever (Bartonella quintana)


TYPES OF CUTANEOUS TB



  • From external exposure:



    • Primary inoculation


    • Tuberculosis verrucosa cútis


    • Tuberculosis cutis orificialis (orificial TB)


  • From hematogenous spread:



    • Lupus vulgaris


    • Miliary tuberculosis


  • From direct extension:



    • Scrofuloderma


  • Reactive eruptions to TB (tuberculid eruptions):



    • Papulonecrotic tuberculid


    • Lichen scrofulosorum


    • Erythema induratum


CATEGORIES OF DEPOSITIONAL DISEASES



  • Mnemonic = MACULE1



    • Mucin


    • Amyloid


    • Calcium


    • Urate


    • Lipid


    • Exogenous/extra (implanted, pigment, hyaline-like)


15.2 Associations and Work-Ups



15.2.1 Disease-Specific Associations




HCV SKIN ASSOCIATIONS



  • (by direct effect and as consequence of associated hepatic damage)



    • Cutaneous necrotizing vasculitis (as in type II cryoglobulinemia), usually presents with palpable purpura, can see livedo reticularis, urticaria


    • Porphyria cutanea tarda (may have HCV association)


    • Lichen planus – stronger association with mucosal/ulcerative LP


    • Cutaneous B-cell lymphoma


    • Xerostomia


    • Erythema multiforme (possibly)


    • Pruritus (in 15 % of patients with HCV)


    • Necrolytic acral erythema


LIVER DISEASE ASSOCIATIONS ON DERM PHYSICAL EXAM



  • Prurigo and excoriations (from generalized pruritus)


  • Asterixus/tremor


  • Palmar erythema


  • Spider angiomas


  • Caput medusae


  • Gynecomastia


  • Scleral icterus


  • Terry’s nails


HIV SKIN ASSOCIATIONS



  • Candidiasis (thrush)


  • Exuberant seborrheic dermatitis


  • HPV infection/diffuse verruca vulgaris/condyloma acuminata


  • Herpes zoster (and disseminated zoster)


  • Molluscum contagiosum (giant, diffuse)


  • Kaposi’s sarcoma


  • HIV-associated eosinophilic folliculitis


  • Papular pruritic eruption of HIV


  • Lipodystrophy – associated with protease inhibitors (specifically indinavir), NRTIs


  • Bacillary angiomatosis


  • Exanthem of seroconversion


  • Oral hair leukoplakia (EBV)


  • Deep fungal infection (Cryptococcosis, Histoplasmosis)


  • Reactive arthritis (psoriasiform)


  • Proximal subungual onychomycosis due to T. rubrum


  • Pruritus/prurigo


  • Stevens-Johnson syndrome (1000× greater incidence); other drug reactions with increased frequency also


  • Acquired ichthyosis


  • Psoriasis


DERM CONDITIONS ASSOCIATED WITH DIABETES



  • Acanthosis nigricans


  • Acrochordons


  • Diabetic dermopathy (“shin spots”)


  • Necrobiosis lipoidica (NLD)


  • Scleredema


  • Granuloma annulare


  • Diabetic bullae (bullosis diabeticorum)


  • Necrotizing fasciitis


  • Erythrasma


  • Mucormycosis


  • Malignant external otitis


RASH IN PATIENT WITH KNOWN MALIGNANCY DDX

1.

Medications (often on many antibiotics, chemo, allopurinol)

 

2.

Metastatic disease

 

3.

Reactive (GVHD, Sweet’s)

 

4.

Infectious disease (immunosuppressed and vulnerable)

 


UMBILICATED PAPULES



  • Poxviruses



    • Molluscum


    • Smallpox (Variola)


    • Cowpox (Vaccinia)




  • Herpes viruses



    • HSV-1 and 2, herpes simplex


    • VZV, varicella and zoster


MOLLUSCUM MASQUERADERS (umbilicated papules) IN HIV PATIENT



  • Mnemonic = CCHP



    • Coccidiodomycosis


    • Cryptococcosis


    • Histoplasmosis


    • Penicilliosis


15.2.2 Work-Ups




CLINICAL EXAMINATION OF THE WHITE MACULE



  • Check for scale – tinea versicolor


  • Check for blanching – nevus anemicus


  • Check with Wood’s lamp – vitiligo


  • Check for anesthesia – leprosy (more in borderline/tuberculoid)

Also remember: PIPA, MF, tuberous sclerosis (ash leaf macules), pityriasis alba, progressive macular hypomelanosis, sarcoidosis

HOW TO WORK UP A PUSTULAR ERUPTION



  • Check Tzanck or viral culture (to r/o HSV or VZV)


  • Check gram stain/bacterial culture (to r/o bacterial impetigo)


  • Check KOH (to r/o candidiasis/tinea)


  • Check mineral oil (to rule in scabies)


  • Check Wright stain (for eosinophils – to rule in erythema toxicum neonatorum or incontinentia pigmenti)


GENERALIZED PRURITUS WORK-UP



  • Is there a primary skin disease? If not, then search for internal cause of itch.



    • Check for dermatographism (urticaria)


    • Check for xerosis on exam


    • Check mineral oil (rule in scabies)


    • Check CBC (for eosinophilia – allergy/neoplasm/parasite, for elevated Hgb – polycythemia vera, other signs of hematologic malignancy)


    • Check BMP: BUN/Cr for renal disease, elevated glucose may suggest diabetes


    • Check LFTs for liver/cholestatic etiology


    • Check HIV, hepatitis B and C serologies


    • Check TSH to r/o hyperthyroidism


    • Check CXR, r/o Hodgkin’s lymphoma


    • Check SPEP/UPEP to r/o monoclonal gammopathy


    • All age-appropriate cancer screening up to date?


SYSTEMIC VASCULITIS WORK-UP



  • Assess for systemic involvement: U/A for blood (GU involvement), stool guaiac (GI involvement); CBC and CMP


  • Consider etiologies:



    • Medication history


    • Connective tissue disease (ANA, Rf, C3, C4, Ro, La)


    • Infectious disease (HIV, hepatitis serologies, ASLO)


    • Other inflammatory (cryoglobulins, p-ANCA, c-ANCA)


RETIFORM PURPURA WORK-UP



  • Complete systemic vasculitis work-up (as above)


  • Check PT, PTT, platelets (r/o DIC)


  • Consider ECHO (if septic vasculitis is a consideration) and follow blood cultures


  • Has patient been on warfarin (warfarin necrosis) or heparin (heparin-induced thrombocytopenia thrombosis and necrosis)?


  • Any cocaine history? Consider urine toxicity for cocaine (cocaine/levamisole-associated vasculopathy)


ERYTHEMA NODOSUM WORK-UP



  • CXR – r/o hilar lymphadenopathy (sarcoid)


  • PPD – r/o TB


  • ASLO – r/o Strep


  • Consider β-HCG in young women


URTICARIA WORK-UP



  • Consider medication and food history, connective tissue disease (ANA, Rf, Ro, La), thyroid disease (TSH), infection (HIV, hepatitis serologies, ASLO)


ALOPECIA WORK-UP



  • Clinical exam: Any scalp disease? Any hair shaft abnormalities? Check hair pull.


  • Consider CBC, ferritin, vitamin D, zinc, TSH, hormonal evaluation: FSH/LH (depends on stage in menstrual cycle), prolactin, free testosterone (from gonads), DHEAS (from adrenals).


15.3 Acronyms



15.3.1 List of Acronyms



15.3.1.1 Important Acronyms


Dermatologists use way too many acronyms, but here is a list of the most common you might not know. Use as needed, but remember that many frown upon their use, especially in clinical notes that may be shared with non-dermatologists. It is easy to get used to using acronyms and forget what they mean. If you do use an acronym, make sure you know what it stands for!



  • AFX = atypical fibroxanthoma


  • AGEP = acute generalized exanthematous pustulosis


  • AK = actinic keratosis


  • ALHE = angiolymphoid hyperplasia with eosinophilia


  • BCC = basal cell carcinoma


  • BCIE = bullous congenital ichthyosiform erythroderma (EHK)


  • BP = bullous pemphigoid


  • BSA = body surface area


  • BXO = balanitis xerotica obliterans (lichen sclerosus of the penis)


  • CALM = café-au-lait macule


  • CARP = confluent and reticulated papillomatosis (of Gougerot and Carteaud)


  • CCCA = central centrifugal cicatricial alopecia


  • CTCL = cutaneous T-cell lymphoma


  • DEJ = dermal-epidermal junction, aka basement membrane zone (BMZ)


  • DF = dermatofibroma


  • DFA = direct fluorescent antibody (test for herpes simplex and zoster)


  • DFSP = dermatofibrosarcoma protuberans


  • DH = dermatitis herpetiformis


  • DIF = direct immunofluorescence


  • DLE = discoid lupus erythematosus


  • DM = may refer to dermatomyositis or diabetes mellitus


  • DN = dysplastic (atypical) nevus aka Clark’s nevus


  • DPN = dermatosis papulosa nigra (easy to confuse which word ends in osis!)


  • DRESS = drug rash with eosinophilia and systemic symptoms (hypersensitivity reaction)


  • DSAP = disseminated superficial actinic porokeratosis


  • EAC = erythema annulare centrifugum


  • EB = epidermolysis bullosa


  • EBA = epidermolysis bullosa acquisita


  • EDP = erythema dyschromicum perstans


  • EDV = epidermodysplasia verruciformis


  • EED = erythema elevatum diutinum


  • EHK = epidermolytic hyperkeratosis (pathology term for finding in bullous congenital ichthyosiform erythroderma)


  • EIC = epidermal inclusion cyst aka follicular/epidermoid/sebaceous cyst


  • EM = erythema multiforme


  • EPF = eosinophilic pustular folliculitis


  • EPP = erythropoietic protoporphyria


  • EPS = elastosis perforans serpiginosa


  • FEP = fibroepithelial polyp (skin tag/acrochordon)


  • GA = granuloma annulare


  • GVHD = graft versus host disease


  • HC = hydrocortisone


  • HS = hidradenitis suppurativa


  • IDN = intradermal nevus


  • ILK = intralesional Kenalog (triamcinolone)


  • ILVEN = inflammatory linear verrucous epidermal nevus


  • IPL = intense pulsed light


  • IVIg = intravenous immunoglobulin (IgG)


  • JXG = juvenile xanthogranuloma


  • KA = keratoacanthoma


  • KP = keratosis pilaris


  • KS = Kaposi’s sarcoma


  • LCV = leukocytoclastic vasculitis (small-vessel vasculitis dermpath pattern)


  • LE = lupus erythematosus


  • LGV = lymphogranuloma venereum


  • LP = lichen planus


  • LPLK = lichen planus-like keratosis


  • LPP = lichen planopilaris


  • LS and A (LS et A) = lichen sclerosus et atrophicus (technically just lichen sclerosus now)


  • LSC = lichen simplex chronicus

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Oct 6, 2016 | Posted by in Dermatology | Comments Off on Lists, Common Differential Diagnoses, and Mnemonics

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