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Don’t Miss It: Common Misleading Diagnoses

During the Fall 2014 SDPA Conference, Jason Roddick, PA-C shared his pearls on how to catch those tricky conditions that don’t always appear on the patient as they do in the text book.


Jason Roddick, PA-C lectured on alternative presentations of some common dermatitis and lesions that can be misleading.  Roddick noted that differential consideration is essential for becoming a better clinician as well as avoiding malpractice suits for you and your practice.  “Remember not all things come in looking like a text book photo or a Google image,” said Roddick.  He continued, “Believe in your ability to diagnose, then trust in your ability to be wrong.”  Roddick listed some of the common misleading diagnoses, why they’re missed, and how to avoid missing them.


Bowen’s Disease

What we know:

Also known as SCCis

On genitals or oral mucosa: Erythroplasia of Queryrat.

Tx: as you would SCC in site. Treatment depends on size, sight, and severity

Why it’s missed:

Similar to plaque-like or eczematous eruptions

Look for dermatitis treatment failures in isolated areas especially in those that are sufficiently sun damaged

Can mimic seborrheic dermatitis

Erythroplasia of Queyrat

          May be misdiagnosed for Balanitis especially candidiasis or psoriasis.

          If treatment is failing, consider this condition.


Subacute Lupus Erythematous (LE)

Lupus represents a quagmire of different presentations, triggers, and causes.

Subacute Cutaneous Lupus Erythematous however, can present much differently than most Lupus Erythematous presentations.



May last months similar to DLE

May be drug induced: HCTZ (Pr/SSA antibody) and Ca++ channel blockers

Rarely below the waist, spares the knuckles (this differentiates it from the psoriasis)

Can create telangiectasia post-eruption

Presents similarly to polymorphous light eruption


Why do we miss it?

Mild cases that have telangiectasia to face can present as actinic damage or rosacea

Mild cases can present similar to photodermatitis, asteatosis and sometimes LSC

*If you don’t add this one into your diagnosis repertoire, you’ll likely miss it.



History, History, History

Scabies presentation are NOTORIOUSLY polymorphous and do NOT require “burrows.”

Many people may present with vague symptoms of itch. Still predominates night/evening hours.



We all understand and know the ABCDEs of Melanoma

Be aware of lesions that persist, ulcerate, or hemorrhage.

Many melanoma can appear red vs. “dark.”

Australian Journal of Dermatology, May 2014 Describes melanomas present as red nodules– “looking or presenting like pimples”


What to watch for:

Firm nodules or lesions growing progressively for 1 month or more.

*Do NOT fear a biopsy.

*Melanoma tends to be the big lawsuit risk


Disseminated Granuloma Annulare

Could be confused with:

Intertrigo with satellite lesions: it will look dry and so other diagnosis may fit the bill

Dermatosis: In this one, if you treat this like to treat other dermatosis, you won’t get anywhere

Can present itself outside of the common ringed, elevated, sharply circumscribed, eruption.

On lower legs, below knees, can present similar to stasis dermatitis.

GA has been found after trauma, UV light exposure, and others, but rarely are comorbidities associated.

Can present similar to Lichen Planus, early Necrobiosis Lipoidica.

Treatments typically require systemic affect to be effective: dapsone, isotretinoin, etretinate, hydroxychloroquine, niacinamide, cyclosporine, and PUVA


Rocky Mountain Fever

Caused by Tick bite, passing R. rickettsii.

Predominant in 5 to 9 year olds

Over 90% of infections occur spring through summer when the deer tick is active.

ONLY 3-18% of patients present with rash, fever, and a history of tick exposure on first visit

Why this is important:

Delay in diagnosis (after 5 days of illness) increases risk of fatality.

What to look for:

Fever (could be short-lived), headache, rash, and myalgia is used because tests can’t confirm for 10 + days typically.

Get a GOOD history

Can present as Disseminated Intravascular Coagulation

Do not confuse with Schamberg’s disease as well, especially for the adults

May be wise to treat with Doxycycline if you think that it may be Rocky Mountain Fever



Can be from several causes or etiologies.

1. Fungal?

2. Erythrasma? (bacterial source)

3. Psoriasis


Patient compliance, and recurrences can often lead to confusing diagnosis.

Do not let patient’s poor compliance deter your diagnosis.

Ask patient to bring the tube in when in doubt.

The etiology of the condition can be multiple. It IS possible to have bacteria AND fungal playing a role in the condition.

Obesity and occupation can play significant role.

Systemic therapy is sometimes required. Build patient confidence by getting results quickly.

Recurrence is common in certain etiologies; especially with body habits, weather, and hygiene concerns.


Perioral Dermatitis

Some differentials to consider:

Seborrheic dermatitis

Herpes simplex virus

It’s not always missed, but it is exacerbated by patient intervention

Patients often “intervene” with therapy using OTC acne products, cortisones, alpha and/or beta hydroxy products, or prescribed acne products (tretinoin as an example) exacerbating condition.

Patients often self-diagnose and treat as “acne,” thus continuing treatments in ADDITION to what clinician prescribed.


Image: estherase

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