What diagnostic workup should be performed for a patient with a rash and potential systemic involvement?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: June 6, 2025 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

From the Guidelines

The diagnostic workup for a patient with a rash and potential systemic involvement should include a total body skin examination, complete review of systems, and laboratory tests such as CBC with DIFF, liver, and kidney function tests, as well as consideration of skin biopsies and serial clinical photography. This approach is supported by the most recent and highest quality study, which emphasizes the importance of a thorough evaluation to rule out other etiologies of the skin problem and to assess for potential systemic involvement 1.

Key Components of Diagnostic Workup

  • Total body skin examination with attention to examining all mucous membranes
  • Complete review of systems to assess for potential systemic involvement
  • Laboratory tests, including:
    • CBC with DIFF
    • Liver function tests
    • Kidney function tests
    • Consideration of urinalysis (UA) in the context of DRESS to assess for associated nephritis
  • Consideration of skin biopsies to assess for full-thickness epidermal necrosis or other possible etiologies
  • Serial clinical photography to monitor the progression of the rash

Additional Considerations

  • Rule out other etiologies of the skin problem, such as infection, effect of another drug, or skin condition linked to another systemic disease 1
  • Consider referral to a dermatologist if autoimmune skin disease is suspected 1
  • Consider clinical monitoring with use of serial clinical photography 1
  • If mucous membrane involvement or blistering is noted on the skin, consider early admission to a burn center for further monitoring and management 1

From the Research

Diagnostic Workup for Rash with Potential Systemic Involvement

To approach a patient with a rash and potential systemic involvement, a thorough diagnostic workup is essential. The following steps can be considered:

  • Complete Blood Count (CBC): A CBC is a fundamental test that can provide valuable information about the patient's condition. It evaluates the total numbers and characteristics of cell components in the blood, including white blood cell (WBC) count, neutrophil-to-lymphocyte ratio (NLR), hemoglobin (Hb) level, mean corpuscular volume (MCV), red cell distribution width (RDW), platelet count, mean platelet volume (MPV), and platelet-to-lymphocyte ratio (PLR) 2.
  • Physical Examination: A thorough physical examination is crucial to assess the extent and characteristics of the rash, as well as to identify any other signs of systemic involvement.
  • Medical History: Obtaining a detailed medical history can help identify potential underlying causes of the rash and systemic symptoms.
  • Additional Tests: Depending on the patient's presentation and medical history, additional tests such as blood cultures, serologic tests, or imaging studies may be necessary to rule out specific conditions.
  • Dermatological Examination: A dermatological examination can help determine the type and cause of the rash, and may involve procedures such as skin biopsies or scrapings.
  • Systemic Involvement Evaluation: Evaluation for systemic involvement may include tests such as liver function tests, renal function tests, or inflammatory marker tests, depending on the suspected underlying condition 2.

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Related Questions

What are the appropriate physical exam questions, workup, and laboratory tests to order for a 15-year-old female patient?
What is the appropriate workup for a 35-year-old patient who experiences a sensation of chest heaviness since undergoing knee surgery on November 15th, 2024, and reports possible inhalation of aluminum particles from his car's air conditioning (AC) system during valve replacement?
What labs or tests should be ordered for a 44-year-old male with a history of colon cancer, Chronic Obstructive Pulmonary Disease (COPD), and a body mass index (BMI) of 50, presenting with dyspnea, fatigue, and cough?
What is the cause of fatigue in a 60-year-old male?
What is the recommended workup for a 13-year-old male with failure to thrive (FTT), weighing 60 pounds, despite a normal appetite, after ruling out diabetes mellitus?
What do microangiopathic hypodensity foci in the brain signify?
Is nifedipine used more for rate control or blood pressure control?
What is the recommended management plan for a postpartum patient with Hashimoto's thyroiditis, normal TSH level, and currently taking 50mcg of levothyroxine (T4)?
What is the recommended protocol for a knee joint injection, specifically the medication and dosage?
At what age should a patient have their next colonoscopy (colon examination) if their mother had precancerous colon polyps at age 50 and they had a normal colonoscopy at age 31?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question