About

Thomas D. Keenan MD, PhD is an Associate Professor and the Director of the Dermatology Consult Service at the University of Wisconsin-Madison. He completed his M.D./Ph.D. at Mayo Medical School in Rochester, Minnesota in 2011, following his undergraduate studies at Boston University where he earned a B.A. in Biology with Magna Cum Laude honors in 2001. His professional memberships include the American Academy of Dermatology (2011-present) and the American Medical Association (2003-present). Keenan's role involves clinical dermatology, with a focus on dermatology consultation services, and he is actively involved in the academic and clinical training within the Department of Dermatology at UW-Madison.

Research topics

• Medicine
• Dermatology
• Pathology
• Computer Science
• Emergency medicine
• Surgery
• Immunology
• Internal medicine
• Medical emergency
• Psychiatry

Selected publications

• Misdiagnosis of cellulitis in the emergency department and potential impact of clinical decision support interventions

  The American Journal of Emergency Medicine · 2025-09-25 · 1 citations

  articleOpen access
  PublisherOA PDFDOI

• Validation of Thermal Imaging and the ALT-70 Prediction Model to Differentiate Cellulitis From Pseudocellulitis

  JAMA Dermatology · 2024-03-27 · 11 citations

  letterOpen access

  Importance: Cellulitis is misdiagnosed in up to 30% of cases due to mimic conditions termed pseudocellulitis. The resulting overuse of antibiotics is a threat to patient safety and public health. Surface thermal imaging and the ALT-70 (asymmetry, leukocytosis, tachycardia, and age ≥70 years) prediction model have been proposed as tools to help differentiate cellulitis from pseudocellulitis. Objectives: To validate differences in skin surface temperatures between patients with cellulitis and patients with pseudocellulitis, assess the optimal temperature measure and cut point for differentiating cellulitis from pseudocellulitis, and compare the performance of skin surface temperature and the ALT-70 prediction model in differentiating cellulitis from pseudocellulitis. Design, Setting, and Participants: This prospective diagnostic validation study was conducted among patients who presented to the emergency department with acute dermatologic lower extremity symptoms from October 11, 2018, through March 11, 2020. Statistical analysis was performed from July 2020 to March 2021 with additional work conducted in September 2023. Main Outcomes and Measures: Temperature measures for affected and unaffected skin were obtained. Cellulitis vs pseudocellulitis was assessed by a 6-physician, independent consensus review. Differences in temperature measures were compared using the t test. Logistic regression was used to identify the temperature measure and associated cut point with the optimal performance for discriminating between cellulitis and pseudocellulitis. Diagnostic performance characteristics for the ALT-70 prediction model, surface skin temperature, and both combined were also assessed. Results: The final sample included 204 participants (mean [SD] age, 56.6 [16.5] years; 121 men [59.3%]), 92 (45.1%) of whom had a consensus diagnosis of cellulitis. There were statistically significant differences in all skin surface temperature measures (mean temperature, maximum temperature, and gradients) between cellulitis and pseudocellulitis. The maximum temperature of the affected limb for patients with cellulitis was 33.2 °C compared with 31.2 °C for those with pseudocellulitis (difference, 2.0 °C [95% CI, 1.3-2.7 °C]; P < .001). The maximum temperature was the optimal temperature measure with a cut point of 31.2 °C in the affected skin, yielding a mean (SD) negative predictive value of 93.5% (4.7%) and a sensitivity of 96.8% (2.3%). The sensitivity of all 3 measures remained above 90%, while specificity varied considerably (ALT-70, 22.0% [95% CI, 15.8%-28.1%]; maximum temperature of the affected limb, 38.4% [95% CI, 31.7%-45.1%]; combination measure, 53.9% [95% CI, 46.5%-61.2%]). Conclusions and Relevance: In this large diagnostic validation study, significant differences in skin surface temperature measures were observed between cases of cellulitis and cases of pseudocellulitis. Thermal imaging and the ALT-70 both demonstrated high sensitivity, but specificity was improved by combining the 2 measures. These findings support the potential of thermal imaging, alone or in combination with the ALT-70 prediction model, as a diagnostic adjunct that may reduce overdiagnosis of cellulitis.

  PublisherOA PDFDOI

• Histopathologic evidence of <scp>chimeric antigen receptor T‐</scp>cell therapy in lesions of <scp>B‐cell</scp> lymphoblastic leukemia cutis

  Journal of Cutaneous Pathology · 2024-02-17

  articleOpen accessSenior author

  Chimeric antigen receptor T-cell (CAR-T) therapy is a form of potent immune effector cell therapy for relapsed lymphoid and plasma cell malignancies.1 Evidence of the cytotoxic effects mediated by CAR-T has been reported primarily in preclinical in vivo and in vitro models.2 Demonstration of pathological features in patients during active therapy is challenging, and therefore limited, owing to the nature of the hematologic malignancies. Here, we present a case of refractory B-cell acute lymphoblastic leukemia (B-ALL) with known leukemia cutis (LC) that clinically flared in response to initiation of CAR-T therapy and present serial dermatopathology of LC prior to and during CAR-T therapy. A 36-year-old male with refractory B-ALL and a history of biopsy-proven LC (resolved 8 months prior) presented with asymptomatic, deep red-to-violaceous nodules on the back (Figure 1A) while receiving blinatumomab infusions. Punch biopsies demonstrated infiltrative blastic-appearing mononuclear cells (Figure 1B,C) that stained positive for CD19, CD34, TdT, and PAX-5 (Figure 1C–G), consistent with recurrent LC. Imaging demonstrated cystic and necrotic-appearing cervical, thoracic, and pelvic lymphadenopathy, later confirmed as recurrent B-ALL on biopsy, though bone marrow biopsy exhibited morphologic complete remission (CR) with measurable residual disease (MRD) by flow cytometry. We pursued CAR-T as a bridge to curative stem cell transplantation (SCT), given high risk disease. After T-cell harvesting, the patient underwent 7 weeks of lymphodepletion with IV fludarabine 25 mg/m2 and IV cyclophosphamide 900 mg/m2, before receiving an infusion of 1 × 108 CAR-positive viable T-cells. During lymphodepleting chemotherapy patient had significant improvement and near resolution of LC lesions. Clinical course following CAR-T was remarkable for grade II cytokine release syndrome (CRS) treated with tocilizumab. On Day 6 of therapy, patient again developed infiltrative reddish-orange, round plaques and nodules, first at the site of prior LC, and later involving the scalp, right cheek, left infraorbital skin, and bilateral extremities (Figure 2A). Biopsy of lesions demonstrated a population of lymphocytes expressing CD19, PAX-5, TdT, and CD34 consistent with the patient's known LC, as well as T-cell infiltrate, extensive cellular debris, and hemophagocytosis, suggesting a cytotoxic response to treatment (Figure 2B–H). The patient developed CRS with peak ferritin levels reaching 15 177 ng/mL suggesting systemic hyperinflammation with some overlapping features but not fully meeting criteria for hemophagocytic lymphohistiocytosis-like toxicity of CAR-T therapy (carHLH) as the patient did not have involvement of ≥2 organs.3 The patient's clinical recrudescence of LC with associated CRS and histopathologic findings was thought to represent response to CAR-T and CRS eventually resolved with supportive therapy. The cutaneous lesions improved following CAR-T therapy and repeat imaging and bone marrow biopsy confirmed CR and no MRD of the B-ALL. Two months later, patient received a planned 8/8 matched unrelated donor peripheral blood SCT. At the latest follow-up, patient remains in CR with no evidence of disease recurrence. In this report, we describe a case with convincing serial pathology demonstrating LC responding to CAR-T therapy. Histopathology in the days following infusion of CAR-T cells demonstrated a cutaneous leukemic infiltrate with immunohistochemical phenotype matching that of patient's known B-ALL with addition of hemophagocytosis and extensive cellular debris in association with significant T-cell infiltrates. CAR-T cells have previously been shown to be able to infiltrate the skin and eliminate covert LC.4 Case reports have also demonstrated flaring of LC in response to CAR-T and that disease flare may not necessarily be indicative of CAR-T therapy failure.4, 5 This report adds to this knowledge by demonstrating serial histopathology consistent with CAR-T cells at work within leukemic infiltrates.4, 5 Additionally, our case highlights that hemophagocytosis could also be an attribute of effector function of CAR-T, a known extreme variant of CRS, carHLH.6, 7 Indeed, the flare of LC and the noted T-cell infiltrate with cellular debris and phagocytosis following CAR-T infusion likely indicate a favorable response, but data are limited to allow definitive conclusions about the long term prognostic and predictive value of this finding. Prospective histopathologic correlates with long-term follow-up of LC patients undergoing CAR-T would provide further insights. The authors declare no conflicts of interest. Data sharing not applicable to this article as no datasets were generated or analyzed during the current study.

  PublisherOA PDFDOI

• Granuloma Annulare Exhibits Mixed Immune and Macrophage Polarization Profiles with Spatial Transcriptomics

  Journal of Investigative Dermatology · 2024-06-05 · 4 citations

  articleOpen access
  PublisherOA PDFDOI

• Comparing skin surface temperature to clinical documentation of skin warmth in emergency department patients diagnosed with cellulitis

  Journal of the American College of Emergency Physicians Open · 2022 · 2 citations

  • Computer Science
  • Medicine
  • Dermatology

  Objective: To compare clinical documentation of skin warmth to patient report and quantitative skin surface temperatures of patients diagnosed with cellulitis in the emergency department (ED). Methods: Adult patients (≥18 years) presenting to the ED with an acute complaint involving visible erythema of the lower extremity were prospectively enrolled. Those diagnosed with cellulitis were included in this analysis. Participant report of skin warmth was recorded and skin surface temperature values were obtained from the affected and corresponding unaffected area of skin using thermal cameras. Average temperature (Tavg) was extracted from each image and the difference in Tavg between the affected and unaffected limb was calculated (Tgradient). Clinical documentation of skin warmth was compared to patient report and measured skin warmth (Tgradient >0°C). Results: = 0.0083). No association was found between Tgradient and patient-reported or HPI-documented warmth. Conclusions: The majority of ED-diagnosed cellulitis exhibited objective warmth, yet significant discordance was observed between patient-reported, clinician-documented, and measured warmth. This raises concerns over inadequate documentation practices and/or the poor sensitivity of touch as a reliable means to assess skin surface temperature. Introduction of objective temperature measurement tools could reduce subjectivity in the assessment of warmth in patients with suspected cellulitis.

  PublisherOA PDFDOI

• 1033. Skin Surface Thermal Imaging to Differentiate Cellulitis and Pseudocellulitis in the Emergency Department

  Open Forum Infectious Diseases · 2021-11-01

  articleOpen access

  Abstract Background Cellulitis is misdiagnosed in up to 30% of cases, resulting in overuse of antibiotics. This represents a threat to patient safety and public health. Surface thermal imaging has been proposed as a tool to reduce errors in diagnosing cellulitis. The study objective was to compare skin surface temperature measurements between patients with cellulitis and pseudocellulitis. Methods We prospectively enrolled patients presenting to the emergency department (ED) with dermatologic lower extremity complaints that involved visible erythema. Using a thermal imaging camera, the maximum temperature value (Tmax) for the affected area of skin and corresponding area on an unaffected limb were captured. The Tmax gradient between the affected and unaffected limb was calculated. Gold standard diagnosis (cellulitis versus pseudocellulitis) was determined by consensus of a blinded, multidisciplinary physician review panel (two infectious disease, two dermatologists and two emergency medicine). Differences in temperature variables (Tmax and Tmax gradient) between cellulitis and pseudocellulitis were compared using t-tests. Results The sample included 204 participants, 59% male with an average age of 57 years. Based on expert panel consensus diagnosis, 92 (45%) of the participants had cellulitis. The cellulitis group had an average Tmax of 33.2°C and 30.2°C for affected and unaffected skin respectively, which was a significant difference of 2.9°C (CI: 2.5 to 3.6; p&amp;lt; 0.001). The difference in the Tmax gradients between patients with cellulitis and pseudocellulitis was 2.08°C (CI: 1.46-2.70; p&amp;lt; 0.001). Conclusion This represents the largest validation study of skin surface temperature differences between cellulitis and pseudocellulitis. Significant difference in temperature gradients between cases of cellulitis and pseudocellulitis suggests thermal imaging could be a useful diagnostic adjunct that can help differentiate these conditions. Such a modality could be particularly helpful in the ED setting where providers must balance diagnostic uncertainty with antimicrobial stewardship principles. Future work will identify the best performing temperature variables and determine optimal cutoff values for use in diagnostic algorithms. Disclosures All Authors: No reported disclosures

  PublisherDOI

• Clinical features of tumor necrosis factor-α-inhibitor induced chilblain lupus: A case series

  JAAD Case Reports · 2021 · 6 citations

  • Medicine
  • Dermatology
  • Immunology

  Lupus erythematosus is an autoimmune disorder with variable presentations and extent of involvement, including systemic lupus erythematous (SLE), subacute cutaneous lupus erythematosus (SCLE), and chronic cutaneous lupus erythematosus (CCLE). SLE is a multisystem disorder, with malar erythema and photosensitivity as common findings. Chilblain lupus is a rare variant of CCLE, manifesting clinically as erythematous, dusky papules on acral sites, which can be pruritic or painful. Chilblain lupus is associated with SLE in up to 20% of cases, particularly if discoid lupus plaques are present.

  PublisherDOI

• Fracture treatment in the setting of cutaneous aspergillosis: a case report

  OTA International The Open Access Journal of Orthopaedic Trauma · 2020-08-04 · 1 citations

  articleOpen access

  Abstract The authors present the case of a patient who developed an Aspergillosis flavus ( A flavus ) superficial cutaneous infection which was identified at the time of cast removal, 2 weeks after immobilization of a closed distal third humerus fracture. Clinical and microbiological findings, as well as the treatment of this patient, are reported. An otherwise healthy 27-year-old male presented to the orthopaedic surgery clinic 2 weeks after a closed distal humerus fracture, which was initially immobilized with a functional removable brace. Upon cast removal, the patient was noted to have significant brown hyperkeratotic patches and plaques, studded with pustules in an annular configuration on his left posterior and lateral arm. Fungal culture later grew A flavus . The patient was started on both oral and topical antifungals and operative management of the displaced fracture was delayed until skin lesions resolved. Once clinical examination and negative repeat bedside potassium hydroxide were confirmed, open reduction and internal fixation was performed. The fracture healed uneventfully, and the patient did not develop any signs or symptoms of postoperative infection.

  PublisherDOI

• Intralesional corticosteroid-induced hypopigmentation and atrophy

  Dermatology Online Journal · 2020 · 9 citations

  Senior authorCorresponding
  • Medicine
  • Dermatology
  • Pathology

  Intralesional corticosteroids are associated with various, uncommon, local adverse events [1]. Atrophy and hypopigmentation most commonlyremain localized to sites of injection. However, outward radiation in a linear, streaky pattern has been reported and is termed "perilesional/perilymphatic hypopigmentation or atrophy [2]." We report a case of this rare adverse event.

  PublisherOA PDFDOI

• Occipital alopecia in a young man

  Dermatology Online Journal · 2020-01-01

  articleOpen access

  Lipedematous alopecia is a rare, non-androgenic form of alopecia that is challenging to diagnose, often requiring clinical-pathological correlation. The condition has been reported predominantly in African-American females, but more recently has been described in a broader demographic [1,2]. We describe a rare case of a young Caucasian man with isolated lipedematous alopecia who presented with a boggy, erythematous plaque with alopecia of the occipital scalp and subcutaneous thickening with lymphocytic dermal infiltrate and decreased anagen hairs on histology.

  PublisherOA PDFDOI

Frequent coauthors

• John L. McBride

  University of Melbourne

  6 shared

• Peter T. May

  Monash University

  6 shared

• Paul E. Johnston

  NOAA Physical Sciences Laboratory

  5 shared

• Greg J. Holland

  NSF National Center for Atmospheric Research

  5 shared

• Noel E. Davidson

  4 shared

• Heidi Jacobe

  The University of Texas Southwestern Medical Center

  3 shared

• Robert Redwood

  3 shared

• Bridget E. Shields

  University of Wisconsin–Madison

  3 shared

Labs

• Ahmad LabPI

Education

• B.A., Biology

  Boston University

  2001

• Other

  Mayo Medical School

  2011

Awards & honors

• Virginia Ott Kieckhefer Physician/Scientist Scholarship (200…