Also, different types of psoriasis have variations in their appearance, location, and severity. This is why it’s common to misdiagnose psoriasis or incorrectly diagnose another condition as psoriasis.
Your symptoms may be due to psoriasis. But here are eight medical conditions your healthcare provider will likely consider before coming to that conclusion.
What Can Be Mistaken for Psoriasis
Conditions that may appear similar to psoriasis include:
EczemaSeborrheic dermatitisPityriasis rosea Lichen planusOnychomycosisLupusSquamous cell carcinomaMycosis fungoides
To avoid misdiagnosis, healthcare providers and dermatologists usually do a differential diagnosis to rule out conditions with symptoms similar to psoriasis. When in doubt, they can exclude other possible causes using blood tests, cultures, skin biopsies, and other tools. This allows them to accurately confirm the diagnosis and start the appropriate treatment.
Eczema
Eczema is the name for a group of conditions that cause red, itchy skin patches similar to psoriasis. As opposed to psoriasis, an autoimmune disorder, eczema is characterized by an overactive (rather than self-destructive) immune response.
Eczema tends to be itchier than psoriasis and can cause oozing and crusting when scratched. With psoriasis, the plaques can easily bleed when scratched, leaving behind a peppered pattern of blood spots known as the Auspitz’s sign.
The differences are most apparent under the microscope:
With psoriasis, the skin cells will appear acanthotic (dense and compressed) due to the accelerated speed of skin growth. With eczema, no such compression will be seen.
Seborrheic Dermatitis
Seborrheic dermatitis is a skin condition that mainly affects the scalp, causing scaly patches of red skin and stubborn dandruff. It’s easily mistaken for scalp psoriasis and vice versa.
With psoriasis, the plaques can easily bleed when scratched, leaving behind a peppered pattern of blood spots known as the Auspitz’s sign.
As with eczema, the conditions can be differentiated under the microscope by their acanthotic or non-acanthotic appearance.
Pityriasis Rosea
Pityriasis rosea is a benign skin condition. The name is Latin for “fine pink scale.”
With psoriasis, the flakes are silvery-white with a lamellar (scale-like) appearance. Moreover, psoriatic skin will be dry.
It generally starts with a large, slightly raised, scaly patch on the back, chest, or abdomen. This is called a herald patch. The herald patch is typically followed by the appearance of smaller patches that sweep outward like the boughs of a pine tree.
Pityriasis rosea usually resolves completely within six to eight weeks. Psoriasis is characterized by recurrent flares.
Lichen Planus
Lichen planus is a skin condition thought to be autoimmune. It causes swelling and irritation in the skin, hair, nails, and mucous membranes. Lichen planus can create lacy white patches when it appears in the mouth, vagina, or other mucosal tissues.
Lichen planus will typically manifest with psoriasis-like lesions on the wrists and limbs.
Under the microscope, psoriasis and lichen planus both have an acanthotic appearance. But with lichen planus, there will be a band-like area of damage between the upper layer of skin (epidermis) and the middle layer (dermis).
Onychomycosis
Onychomycosis, also known as tinea unguium, is a fungal infection of the nails.
Lichen planus can also affect mucosal tissues, whereas psoriasis won’t.
Nail psoriasis is frequently mistaken for onychomycosis. They have similar symptoms, like the thickening, crumbling, and lifting of the nail plate, and the formation of abnormal ridges and dents.
Lupus
Systemic lupus erythematosus, also known as lupus, is an autoimmune disease that affects multiple organ systems, including the skin.
A healthcare provider or dermatologist will take a scraping from the nail and examine it under the microscope to confirm the diagnosis. If there are no fungal spores, it can reasonably be assumed that psoriasis is the cause.
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One of the tell-tale signs of lupus is a rash formation on the cheeks and nose. This is called a butterfly rash.
Healthcare providers can usually confirm lupus with a series of blood tests, including the antinuclear antibody (ANA) test. Skin biopsy, including the use of direct and indirect immunofluorescent tests, can also confirm lupus as the cause.
Squamous Cell Carcinoma
Squamous cell carcinoma is the second most common type of skin cancer. It manifests with thick, flat, scaly nodules. It’s usually found on areas of the body damaged by ultraviolet (UV) rays from the sun or tanning beds.
Squamous cell carcinoma can readily be diagnosed with a skin biopsy:
Psoriasis will demonstrate the proliferation of keratinocytes (a type of skin cell found in abundance throughout the epidermis). Squamous cell carcinoma will have a proliferation of squamous cells (the type found mainly on the outer part of the epidermis).
Mycosis Fungoides
Mycosis fungoides, also known as Alibert-Bazin syndrome, is the most common form of cutaneous T-cell lymphoma—a dermatological variation of blood cancer known as non-Hodgkin lymphoma.
Mycosis fungoides manifests with rash-like patches of skin.
The lesions will appear scaly and often be extremely itchy in the early stages. The buttocks are often the first part of the body affected. Over time, the lesions can develop elsewhere, causing widespread redness and itching but far less scaling.
A skin biopsy can help differentiate the diseases. With mycosis fungoides, the biopsied tissue will have microscopic pus-filled cavities in the epidermal layer, known as Pautrier abscesses.
A Word From Verywell
The problem with misdiagnosis is that it can expose you to unnecessary and unhelpful treatments. Worse, by assuming it’s psoriasis without exploring other possible causes, you can miss the signs of a potentially more serious illness. This is why self-diagnosing psoriasis is never a good idea.
Unlike psoriasis, mycosis fungoides is often accompanied by persistently swollen lymph nodes. Pancreas and liver enlargement are also common.
If you’re worried about a skin condition, ask your healthcare provider for a referral to a dermatologist. Mention both skin-related and non-skin-related symptoms. Doing so increases your chance of reaching the correct diagnosis.
