How to Find HS Psoriasis Overlap: Know It

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The intersection of hidradenitis suppurativa (HS) and psoriasis presents a significant diagnostic challenge. While both are chronic inflammatory skin conditions, their overlapping symptoms and shared underlying immunological pathways can lead to misdiagnosis or delayed treatment for patients suffering from both. This guide provides a definitive, in-depth, and actionable framework for identifying the HS-psoriasis overlap, focusing on practical steps for healthcare professionals and empowering patients to advocate for their health.

Unraveling the Dual Diagnosis: A Practical Approach to HS-Psoriasis Overlap

Distinguishing between HS and psoriasis, particularly when they coexist, demands a meticulous and systematic approach. This guide cuts through the complexity, offering clear, actionable strategies to pinpoint the overlap, ensuring accurate diagnosis and optimized management.

Recognizing the Red Flags: Initial Clues for Overlap

The journey to diagnosing HS-psoriasis overlap often begins with recognizing subtle cues during the initial patient encounter. These red flags aren’t definitive on their own but serve as critical indicators prompting further investigation.

Actionable Steps:

  • Beyond the Classic Presentation: Scrutinize Atypical Lesions. While HS classically manifests in intertriginous areas (axillae, groin, gluteal folds) with painful nodules, abscesses, and sinus tracts, and psoriasis presents with well-demarcated, erythematous plaques with silvery scales, an overlap might show atypical presentations.
    • Example: A patient presenting with typical psoriatic plaques on their elbows and knees also reports recurrent, deep-seated, painful nodules in their axillae that don’t quite fit the typical folliculitis pattern, or perhaps exhibit early sinus tract formation. Conversely, an HS patient might suddenly develop new, scaly patches on their trunk or limbs that are distinct from their usual HS lesions.

    • Practical Application: During a skin exam, don’t limit your focus to the primary complaint. Systematically examine all skin surfaces, paying close attention to areas less commonly affected by isolated HS or psoriasis. Are there any psoriatic plaques within HS-affected areas, or vice-versa?

  • Symptom Mismatch: When Pain and Itch Tell a Different Story. Both conditions involve discomfort, but the type and distribution of symptoms can be highly indicative. HS pain is typically deep, throbbing, and associated with inflammation and abscess formation, while psoriatic itch is often described as intensely irritating or burning, and can be widespread.

    • Example: A patient primarily seeking treatment for painful groin lesions (suggestive of HS) mentions persistent, generalized itching and scaling on their scalp and lower back that predates or is independent of their groin symptoms. This prompts exploration of psoriatic involvement.

    • Practical Application: Utilize a detailed symptom questionnaire. Ask not just “Do you have pain?” but “Describe the pain – is it sharp, dull, throbbing? Where is it located? Is it constant or intermittent?” Similarly for itching: “Is it localized or widespread? What makes it better or worse?”

  • Unusual Disease Progression: Deviations from the Norm. If a patient’s condition doesn’t respond as expected to standard treatments for one condition, or if new, seemingly unrelated skin manifestations appear, consider the possibility of an overlap.

    • Example: A patient with long-standing, well-controlled plaque psoriasis suddenly develops painful, recurrent inflammatory nodules in their armpits that are unresponsive to their usual topical corticosteroids or phototherapy. This points towards a new or concurrent HS diagnosis.

    • Practical Application: Maintain a detailed treatment history. Document responses to therapies. If a patient’s condition is refractory to a typically effective treatment, or if new lesion types emerge, widen the diagnostic net.

The Power of Detailed History: Beyond the Chief Complaint

A thorough patient history is paramount in diagnosing HS-psoriasis overlap. It’s not just about what the patient volunteers, but about asking the right questions to uncover hidden clues.

Actionable Steps:

  • Family History: Genetic Predisposition as a Clue. Both HS and psoriasis have strong genetic components. A family history of either condition significantly increases the likelihood of an overlap in a patient.
    • Example: When evaluating a patient with recurrent boils in the groin, asking about family history reveals that their mother has severe psoriasis, and their uncle has experienced similar “boils” throughout his life. This strengthens the suspicion of an overlap.

    • Practical Application: Always include a comprehensive family history in your intake forms or interview process. Specifically ask about skin conditions like psoriasis, “boils,” “abscesses,” or “skin infections” that might represent undiagnosed HS.

  • Comorbidity Checklist: Associated Conditions as Indicators. HS and psoriasis share common comorbidities, including metabolic syndrome, inflammatory bowel disease (IBD), psoriatic arthritis (PsA), and cardiovascular disease. The presence of these can be a strong indicator of an overlap or a predisposition to it.

    • Example: A patient presenting with classic HS lesions also reports persistent joint pain and stiffness, or has a history of Crohn’s disease. These comorbidities are frequently seen in psoriasis and PsA, warranting further investigation for the latter.

    • Practical Application: Systematically inquire about a predefined list of comorbidities during patient interviews. Don’t just ask about joint pain, ask about morning stiffness, swelling, and specific joint involvement. Ask about gastrointestinal symptoms (diarrhea, abdominal pain) suggestive of IBD.

  • Timeline of Onset: Discerning Primary vs. Secondary Conditions. Understanding the chronological development of symptoms can differentiate whether one condition preceded the other, or if they emerged concurrently.

    • Example: A patient states they’ve had psoriasis since adolescence, but only developed painful armpit lumps in their late twenties. This suggests psoriasis as the primary diagnosis with later onset HS. Conversely, a patient with HS since puberty might develop generalized scaling patches later in life.

    • Practical Application: Ask precise questions about the onset of each type of lesion. “When did you first notice the red, scaly patches?” “When did the painful lumps start?” Document these timelines meticulously. This helps in understanding the natural history of their disease presentation.

  • Lifestyle Factors: Smoking and Obesity. Smoking is a major trigger and exacerbating factor for both HS and psoriasis, while obesity is strongly linked to both.

    • Example: A patient with moderate HS who is also a heavy smoker and significantly overweight presents with new, suspicious scaly patches on their elbows. The combined risk factors further support exploring a psoriatic component.

    • Practical Application: Routinely inquire about smoking status and calculate BMI. Counsel patients on the impact of these factors on both conditions, and how addressing them can be part of a comprehensive management plan.

The Focused Physical Examination: Uncovering Hidden Lesions

A targeted and thorough physical examination is crucial. It goes beyond the obvious, seeking out characteristic lesions of both conditions in areas that might be overlooked.

Actionable Steps:

  • Full Skin Survey: Every Crease and Fold Matters. Do not limit the examination to the chief complaint area. Systematically examine all skin surfaces, paying particular attention to areas prone to HS and psoriasis.
    • Example: A patient presents with typical psoriatic plaques on their extremities. A full skin survey reveals subtle, non-inflamed but characteristic “tombstone” comedones in the axillae or inframammary folds, or small, early inflammatory nodules in the groin – all suggestive of HS.

    • Practical Application: Ensure patients are appropriately gowned for a complete skin examination. Use good lighting. Lift skin folds (e.g., breasts, pannus) to visualize hidden areas. Palpate suspicious areas for firmness or tenderness.

  • HS Lesion Morphology: Beyond the Abscess. While abscesses and draining sinuses are hallmark HS features, also look for non-inflamed lesions that are indicative of HS, such as:

    • Double-headed comedones: These are pathognomonic for HS, appearing as blackheads with two or more adjacent follicular openings, often in areas like the axillae or groin.

    • Hypertrophic scars and fibrotic bands: HS causes significant scarring and fibrotic changes due to chronic inflammation. These can appear as rope-like bands under the skin or raised, irregular scars.

    • “Bridge-like” scars: These are unique to HS, formed when sinus tracts heal, leaving raised scar tissue resembling a bridge.

    • Practical Application: Train your eye to recognize these specific HS lesions, even in the absence of active inflammation. They are critical for diagnosing HS, especially in milder forms or during remission, and can guide you towards an overlap.

  • Psoriatic Lesion Morphology: Beyond the Classic Plaque. While classic plaque psoriasis is common, be aware of other psoriatic manifestations:

    • Inverse psoriasis: Smooth, red, non-scaly patches in skin folds (e.g., armpits, groin, under breasts), often mistaken for fungal infections or intertrigo. This is particularly relevant in areas that also harbor HS.

    • Guttate psoriasis: Small, teardrop-shaped scaly lesions, often triggered by streptococcal infection.

    • Pustular psoriasis: Red, tender skin with pus-filled bumps, which can be localized or generalized.

    • Nail psoriasis: Pitting, onycholysis (nail separation), oil spots, and thickening of the nails.

    • Scalp psoriasis: Thick, silvery scales on the scalp, often extending beyond the hairline.

    • Practical Application: Be comprehensive in your assessment. Inspect nails, scalp, and all skin folds. The presence of inverse psoriasis in HS-prone areas can be a strong indicator of overlap.

  • Joint Examination: Screening for Psoriatic Arthritis. Since PsA is a common comorbidity of psoriasis and can also present with features similar to other inflammatory conditions, a basic joint screen is vital.

    • Example: While examining a patient for HS lesions, ask them to demonstrate range of motion in their hands, wrists, and knees. Observe for swelling, tenderness, or limited movement.

    • Practical Application: A quick screening for swollen or tender joints, dactylitis (sausage fingers/toes), or enthesitis (inflammation where tendons or ligaments insert into bone) can prompt a referral to a rheumatologist for further PsA evaluation.

Diagnostic Tools and Investigations: Confirming the Coexistence

While clinical suspicion is high, certain diagnostic tools can help confirm the HS-psoriasis overlap and rule out other conditions.

Actionable Steps:

  • Skin Biopsy: The Definitive Answer (When Necessary). While often not required for a straightforward diagnosis of either HS or psoriasis alone, a skin biopsy can be invaluable in ambiguous cases or when an overlap is suspected.
    • Example: If a lesion presents with features that are atypical for both HS and psoriasis, or if there’s an unusual response to treatment, a biopsy can differentiate. The pathologist can identify characteristic histopathological features of both conditions in separate lesions or even within the same lesion if they are truly overlapping at a microscopic level.

    • Practical Application: When considering a biopsy, select the most representative lesion(s). For HS, aim for an early inflammatory nodule or a sinus tract. For psoriasis, a classic plaque. Communicate your clinical suspicion of overlap clearly to the pathologist to guide their examination.

  • Ultrasound Imaging: Visualizing Subsurface HS Activity. High-frequency ultrasound (HFUS) can visualize the extent of HS lesions below the skin surface, including sinus tracts, inflammatory nodules, and fluid collections, which may not be apparent clinically. While not diagnostic for psoriasis, it helps in assessing the severity and spread of HS.

    • Example: A patient with visible psoriatic plaques also reports pain and swelling in their armpit, but clinical examination is inconclusive. HFUS reveals extensive subclinical sinus tracts and inflammation, confirming the HS component.

    • Practical Application: Consider HFUS for patients with suspected HS, especially if clinical assessment is difficult due to scarring or obesity, or to assess disease activity and extent for treatment planning.

  • Laboratory Tests: Ruling Out Other Inflammatory Conditions. While no specific blood test definitively diagnoses HS or psoriasis, certain markers can help rule out other inflammatory conditions or assess systemic inflammation.

    • Example: Elevated inflammatory markers like C-reactive protein (CRP) or erythrocyte sedimentation rate (ESR) are non-specific but indicate systemic inflammation present in both conditions. In cases of suspected PsA, additional blood tests like rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies can help differentiate from rheumatoid arthritis, although these are often negative in PsA.

    • Practical Application: Order relevant blood tests based on the overall clinical picture. Consider complete blood count (CBC), inflammatory markers, and specific serological tests if other autoimmune or inflammatory conditions are in the differential diagnosis.

Differentiating Mimics: Avoiding Misdiagnosis

Several other skin conditions can mimic aspects of HS or psoriasis, making accurate differentiation crucial for diagnosing overlap.

Actionable Steps:

  • Folliculitis and Abscesses (Bacterial): HS is often misdiagnosed as recurrent bacterial folliculitis or simple abscesses.
    • Differentiation: Bacterial folliculitis typically responds quickly to antibiotics and rarely forms sinus tracts or significant scarring. HS lesions are sterile in their early stages and often recur despite antibiotic treatment, forming characteristic double-headed comedones and fibrotic changes.

    • Practical Application: Consider a bacterial culture of draining lesions to rule out infection, but remember that HS lesions can become secondarily infected. Persistent or recurrent “boils” in intertriginous areas, especially with scarring, should raise suspicion for HS.

  • Cellulitis: A bacterial infection of the deeper layers of the skin.

    • Differentiation: Cellulitis typically presents as a rapidly spreading, erythematous, painful, and warm area with ill-defined borders, often with fever and malaise. It usually responds well to systemic antibiotics. HS lesions are more circumscribed, often chronic, and tend to form discrete nodules and tracts.

    • Practical Application: Assess for systemic signs of infection. If the lesion has a chronic, recurrent nature and lacks rapid spread, it is less likely to be cellulitis.

  • Crohn’s Disease (Cutaneous Manifestations): Cutaneous Crohn’s disease can present with perianal lesions, abscesses, and sinus tracts that mimic HS.

    • Differentiation: A history of gastrointestinal symptoms (abdominal pain, diarrhea, weight loss) is key for Crohn’s. Biopsy of suspicious lesions and investigation for IBD (e.g., colonoscopy, imaging) are crucial.

    • Practical Application: Always inquire about gastrointestinal symptoms in patients with perianal HS-like lesions.

  • Fungal Infections (Intertrigo): Inverse psoriasis can be confused with fungal intertrigo in skin folds.

    • Differentiation: Fungal infections often have satellite lesions and a fine, scaling border. They typically respond to antifungal creams. Inverse psoriasis is usually well-demarcated, smoother, and may respond to corticosteroids but will recur without specific psoriasis treatment.

    • Practical Application: Perform a potassium hydroxide (KOH) prep on skin scrapings from suspicious lesions in skin folds to rule out fungal infection.

  • Seborrheic Dermatitis: Can cause red, scaly patches, particularly on the scalp, face, and chest, overlapping with psoriatic areas.

    • Differentiation: Seborrheic dermatitis scales are usually greasy and yellowish, whereas psoriatic scales are typically silvery and dry. Psoriasis lesions are often more erythematous and well-demarcated.

    • Practical Application: Observe the texture and color of the scales. Psoriasis can also affect the scalp, but it often extends beyond the hairline, which is less common for seborrheic dermatitis.

Collaborative Care: The Interdisciplinary Approach

Diagnosing and managing HS-psoriasis overlap often necessitates a team-based approach, leveraging the expertise of different specialists.

Actionable Steps:

  • Dermatologist’s Role: The Central Figure. The dermatologist is typically the primary specialist for diagnosing and managing both HS and psoriasis. They are adept at recognizing the varied presentations and initiating appropriate treatments.
    • Practical Application: For general practitioners, prompt referral to a dermatologist is crucial when an overlap is suspected or if either condition is severe or atypical.
  • Rheumatologist’s Role: Addressing Psoriatic Arthritis. Given the high prevalence of PsA in psoriasis patients, and its potential to mimic other inflammatory conditions, a rheumatologist is essential for joint assessment and management.
    • Practical Application: Refer patients with new or worsening joint pain, stiffness, or swelling, especially if they have psoriasis, for rheumatological evaluation. Early diagnosis and treatment of PsA are crucial to prevent irreversible joint damage.
  • Gastroenterologist’s Role: Investigating Inflammatory Bowel Disease. The strong association between both HS and psoriasis with IBD (especially Crohn’s disease) warrants gastroenterological evaluation when symptoms are present.
    • Practical Application: If a patient with HS and/or psoriasis reports chronic abdominal pain, diarrhea, or unexplained weight loss, refer them to a gastroenterologist for further investigation.
  • Mental Health Professional’s Role: Addressing Psychosocial Impact. Both HS and psoriasis have significant psychosocial burdens, including depression, anxiety, and impact on quality of life.
    • Practical Application: Screen patients for signs of psychological distress. Offer referrals to psychologists, psychiatrists, or support groups to address mental health challenges and improve coping strategies.
  • Nutritionist/Dietitian’s Role: Managing Comorbidities and Lifestyle. Obesity and metabolic syndrome are common comorbidities. A nutritionist can provide guidance on weight management and anti-inflammatory diets.
    • Practical Application: Counsel patients on the importance of healthy diet and exercise. Refer to a dietitian for personalized nutritional advice, especially for weight management.

Empowering the Patient: Becoming an Active Partner

Patients are invaluable sources of information about their own bodies. Educating them about the possibility of overlap empowers them to advocate for themselves and contribute to a more accurate diagnosis.

Actionable Steps:

  • Educate on “Atypical” Symptoms: Inform patients about the potential for their conditions to manifest in unexpected ways or for new symptoms to appear.
    • Example: “While we’re treating your HS, keep an eye out for any new red, scaly patches on your elbows, knees, or scalp, or any persistent joint pain. These could be signs of another condition that often goes along with HS.”

    • Practical Application: Provide clear, concise information about the common signs and symptoms of both HS and psoriasis, and their potential comorbidities. Use visual aids if possible.

  • Encourage Detailed Symptom Tracking: Provide patients with tools or suggestions for tracking their symptoms, including onset, severity, location, and triggers.

    • Example: Suggest keeping a journal of flare-ups, noting date, location, appearance of lesions, pain level, and any potential triggers.

    • Practical Application: A well-documented symptom diary can provide crucial information, especially when symptoms are intermittent or evolve over time.

  • Promote Open Communication: Foster an environment where patients feel comfortable discussing all their symptoms, even those they may consider unrelated to their primary dermatological concern.

    • Example: “It’s important to tell me about all your symptoms, even if they seem minor or unrelated to your skin. Sometimes, different problems can be connected.”

    • Practical Application: Dedicate sufficient time to patient consultations. Practice active listening. Reassure patients that no symptom is too small or irrelevant to mention.

  • Advocate for Second Opinions and Specialized Care: Empower patients to seek further evaluation if they feel their concerns are not being fully addressed or if their symptoms persist despite treatment.

    • Practical Application: If you are a general practitioner, explain to the patient why a referral to a dermatologist or rheumatologist is beneficial for their complex presentation. For patients, encourage them to ask questions and seek clarity regarding their diagnosis and treatment plan.

Conclusion: A Holistic Vision for Dual Diagnosis

The identification of HS-psoriasis overlap is not merely an academic exercise; it is a critical step towards optimizing patient outcomes. By meticulously scrutinizing red flags, taking comprehensive histories, performing thorough physical examinations, utilizing appropriate diagnostic tools, differentiating mimics, fostering collaborative care, and empowering patients, healthcare professionals can accurately diagnose this complex coexistence. This holistic approach ensures that patients receive timely, targeted, and effective management for both conditions, significantly improving their quality of life and preventing long-term complications. The synergy of vigilance, detailed assessment, and interdisciplinary collaboration is the definitive pathway to understanding and effectively managing the HS-psoriasis overlap.