Psoriasis: How Healthcare Professionals Make a Diagnosis

Oct 01, 2023 By Nancy Miller


The inflammatory skin disorder psoriasis causes red, itchy, and scaly spots. Accelerated skin cell life cycles cause fast cell growth on the skin's surface. The diagnosis of psoriasis is paramount for management and treatment. This article discusses the diverse strategies and methods utilized to diagnose different psoriasis types, offering insight into its varying forms and impact on individuals.

Understanding Psoriasis

Understanding psoriasis is crucial before diagnosing it. Approximately 2-3% of the world's population has psoriasis. It’s a lifelong chronic illness with intermittent flare-ups.

The cause of psoriasis is uncertain. Genetic, immunologic, and environmental variables are involved. Debilitating psoriatic arthritis might result from its skin and joint effects.

Psoriasis Diagnosis

A detailed medical history, physical exam, and sometimes lab testing diagnosis psoriasis. These steps are essential for diagnosing psoriasis and separating it from other skin conditions.

A thorough clinical history is essential for diagnosing psoriasis. The doctor asks about symptoms, disease progression, triggering circumstances, and quality of life. Given psoriasis' hereditary tendency, family history is essential.

Physical Examination

After obtaining a thorough clinical history, a meticulous physical examination is a linchpin in the diagnostic process of psoriasis. This examination involves a comprehensive skin, nails, and scalp assessment. The healthcare provider keenly observes signs of psoriasis, such as erythematous plaques adorned with silvery scales, nail pitting, or onycholysis.

Examination of Lesions

The location, distribution, and severity of the lesions are meticulously evaluated. The provider may scrutinize lesions on the elbows, knees, scalp, and back, areas commonly afflicted by psoriasis. Lesions might also manifest in less familiar areas like the palms, soles, or face, requiring a more exhaustive examination.

Observation of Characteristics

Psoriatic lesions have distinct characteristics. The healthcare provider assesses the plaques' thickness, redness, scaling, and elevation. They also evaluate the presence of any bleeding upon slight abrasion, known as the Auspitz sign, indicative of psoriasis.

Scalp and Nail Examination

A detailed examination of the scalp and nails is vital. The provider looks for scalp scaling and erythema, while nails are assessed for pitting, yellowing, thickening, or separation from the nail bed, signs synonymous with psoriatic involvement.

Documenting Patient Discomfort

The healthcare provider also gauges the level of discomfort, itching, or pain the patient experiences, as these symptoms significantly impact the quality of life and provide insights into the disease’s severity and activity.

Laboratory Tests

Though psoriasis is primarily a clinical diagnosis, there are instances where laboratory tests become indispensable, mainly when the presentation is ambiguous or when other comorbidities are suspected.


A skin biopsy is a pivotal tool for confirming a psoriasis diagnosis. A small sample of damaged skin is extracted and examined under a microscope. Histological traits can assist in diagnosing psoriasis from eczema, dermatitis, and fungal infections.

Blood Tests

In specific scenarios, comprehensive blood tests might be recommended. These tests are not used to diagnose psoriasis per se but serve to rule out other diseases and assess the patient’s overall health. Blood tests are particularly relevant if there are clinical indications of psoriatic arthritis or further systemic involvement. This panel might include a complete blood count, inflammatory markers like CRP and ESR, liver function tests, and rheumatoid factor.

Assessment of Severity

Once the clinical and, if needed, pathological diagnosis is established, the next pivotal step is the evaluation of the disease’s severity. The severity assessment is a cornerstone in formulating a tailored, patient-specific treatment plan.

Utilizing PASI

The Psoriasis Area Severity Index is extensively used for this. This index quantifies psoriasis severity by measuring lesions' extent and severity. The PASI score takes into account the erythema (redness), induration (thickness), and desquamation (scaling) of the lesions, along with the body area affected.

BSA Assessment

Another method involves assessing the Body Surface Area (BSA) affected by psoriasis. This technique estimates the percentage of the body covered by psoriatic lesions, offering insight into the disease’s overall burden.

Quality of Life Impact

The doctor also assesses psoriasis's influence on quality of life. The Dermatology Life Quality Index (DLQI) measures how the illness impacts daily life, emotions, and social interactions.

Considering Co-morbidities

The presence of comorbidities such as psoriatic arthritis, cardiovascular disease, or metabolic syndrome also influences the assessment of severity, as they necessitate comprehensive management strategies.

Differential Diagnosis

Differentiating psoriasis from other skin conditions is imperative for appropriate management. Some conditions that mimic psoriasis include:

  • Eczema: In some instances, eczema resembles psoriasis. However, eczema usually affects joint flexural surfaces and is linked to allergens and asthma.
  • Seborrheic Dermatitis: This condition can mimic scalp psoriasis. It typically presents as greasy, yellowish scales and may be associated with Malassezia yeast.
  • Tinea Infections: Ringworm can present with scaly, circular lesions, necessitating fungal culture or KOH examination for differentiation.

Management and Treatment

After psoriasis is diagnosed, multimodal treatment and psoriasis self-care begins. Psoriasis treatment depends on the kind, severity, location, personal preferences, and health.

  • Tropical Treatments: Topical corticosteroids, vitamin D analogs, and coal tar are used to treat mild to moderate psoriasis.
  • Phototherapy: UV light therapy can help with severe psoriasis or when topical treatments fail.
  • Systemic medications: Methotrexate, cyclosporine, or biologics may treat moderate to severe psoriasis or arthritis.
  • Lifestyle changes: Addressing triggers, eating healthily, decreasing stress, and following a skincare routine can lessen flare-ups and improve quality of life.

Psychosocial Effect

Psychosocial consequences are also diagnosed with psoriasis. Patients with psoriasis often feel stigma, worry, despair, and low self-esteem. Thus, comprehensive care provides psychological assistance and psychotherapy.

Patients' Education

Patient education is essential for psoriasis management. Informing patients on the disease, treatment options, trigger management, and coping strategies improves therapy adherence and quality of life.


Psoriasis diagnosis requires a complete clinical history, physical examination, and sometimes laboratory investigations. Differentiating psoriasis and ruling out other skin disorders is crucial for personalized treatment. Beyond medical interventions, addressing the psychosocial aspects and fostering patient education are integral for holistic care. While psoriasis remains a chronic condition, advancements in understanding and managing the disease offer hope for improved outcomes and quality of life for affected individuals.

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