Hematology Case Study: Monocytosis in An Elderly Patient

An 81 year old presented with fatigue and not feeling too well. CBC revealed marked leukocytosis and monocytosis.

  • White cell count: 85.1 K/uL (elevated)
  • Hemoglobin: 8.6 g/dl (decreased)
  • Platelet count: 79 K/uL ( decreased)

Review of peripheral smear revealed leukoerythroblastosis with monocytosis (19.57 K/uL) along with presence of numerous immature monocytoid cells, dysplastic myeloid precursors and 7% blasts, consistent with myelodysplastic/myeloproliferative neoplasm such as chronic myelomonocytic leukemia-1.






For further evaluation of disease progression and/or transformation to acute leukemia, bone marrow evaluation was recommended.

Diagnostic criteria for chronic myelomonocytic leukemia

  1. Persistent peripheral blood monocytosis >1 K/uL
  2. No Philadelphia chromosome or bcr-abl 1 fusion gene
  3. No rearrangement of PDGFRA or PDGFRB
  4. Fewer than 20% blasts in the blood or bone marrow**
  5. Dysplasia in one or more myeloid lineages.


**Blasts include myeloblasts, monoblasts and promonocytes

Prognosis and predictive factors

Survival of patients with CMML is reported to vary from one to more than 100 months, but the median survival time in most series is 2- to 40 months. Progression to AML occurs in approximately 15-30% of cases. A number of clinical and hematological parameters, including splenomegaly, severity of anemia and degree of leukocytosis, have been reported to be important factors in predicting the course of the disease.


Vajpayee,Neerja2014_small-Neerja Vajpayee, MD, is the director of Clinical Pathology at Oneida Health Center in Oneida, New York and is actively involved in signing out surgical pathology and cytology cases in a community setting. Previously, she was on the faculty at SUNY Upstate for several years ( 2002-2016) where she was involved in diagnostic work and medical student/resident teaching.

Microbiology Case Study: A Routine Sputum Culture on a 20 Year Old Cystic Fibrosis Patient

Case History

A 20 year old woman with cystic fibrosis was routinely screened with bacterial sputum cultures.  The patient reported feeling well and was compliant with her treatment regimen.  She had no history of Nocardia colonization in the past and her last hospitalization was four years prior due to a pulmonary exacerbation in which cultures grew Stenotrophomonas and Pseudomonas.


Image 1: Modified acid fast stain showing two unique traits of Nocardia: long, delicate rods and weak acid fastness.


Image 2: Nocardia colonies on buffered charcoal yeast extract (BCYE) agar.


Nocardia are slow growing, aerobic gram negative rods. Nocardia are unique for being weakly acid fast and displaying aerial hyphae.  They are ubiquitous organisms that can cause a variety of infections in immunocompromised individuals. Most often in the United States, nocardiosis causes a lung infection. If left untreated, it can spread to the brain or spinal cord, where up to 44% die [1].

The above patient showed no signs of an infection, making the possibility of colonization by Nocardia more likely.  Cystic fibrosis patients can be colonized by Nocardia and the clinical approach is to treat regardless of the patient’s overall health. However, there is a lack of reporting on whether Nocardia is the cause of an infection when it happens. Host and pathogen interactions are also not well known. Thorn et al. showed that treating cystic fibrosis patients that are colonized with Nocardia with oral antibiotics did not affect their clinical outcome [2]. More studies are needed to be done to see if antibiotics are warranted in circumstances like the above patient.


  1. Nocardiosis. https://www.cdc.gov/nocardiosis/transmission/index.html
  1. Pulmonary nocardiosis in cystic fibrosis. Thorn, Shannon T. et al.. Journal of Cystic Fibrosis, Volume 8 , Issue 5 , 316 – 320


-Angela Theiss is a pathology resident at the University of Vermont Medical Center.


-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

Chemistry Case Study: Falsely Elevated Methotrexate

High dose methotrexate infusion is widely used in the treatment of malignancies such as leukemia, high risk lymphoma, and osteosarcoma. It can be associated with multiple adverse effects, especially renal toxicity, which could leads to acute kidney injury (AKI), delaying drug elimination and worsening its toxicity. Leucovorin, a reduce folic acid, is commonly used with methotrexate treatment to lessen its toxicity. After administration of methotrexate, serum creatinine and methotrexate concentration should be closely monitored. The levels of serum methotrexate to be associated with a high risk for nephrotoxicity are: 24 h, > 10 μmol/L; 48 h, > 1 μmol/L; 72 h, > 0.1 μmol/L.

In this case, the patient is a 33-yo old male with T-lymphoblastic leukemia in complete remission. He was given consolidation therapy with high dose methotrexate. Leucovorin rescue was given 24 hours after methotrexate administration. Patient’s methotrexate level was at 4.7 μmol/L 3 days postinfusion due to AKI and poor methotrexate clearance. An alternative rescue, glucarpidase (Garboxypeptidase G2), was then given to patient to rapidly lower serum methotrexate level. Glucarpidase cleaves methotrexate molecule to inactive metabolite, DAMPA (2,4-diamino-N-methylpteroic acid). After glucarpidase rescue, patient’s methotrexate level were still remained above the toxic level on the following two days (1.02 μmol/L and 0.68 μmol/L).

In most clinical laboratories, serum methotrexate is measured by immunoassays, and the inactive metabolite of methotrexate after glucarpidase rescue, DAMPA, cross-reacts with immunoassays and interferes the measurement of methotrexate. After glucarpidase treatment, patient’s methotrexate level can be falsely high for 5-7 days, before accurate measurement can be obtained using immunoassays. In this case, the concentrations of methotrexate after glucarpidase rescue were falsely high results due to DAMPA interference. There are laboratory-developed LC-MS methods to detect methotrexate. LC-MS methods are more specific and have no interference from the metabolite, can be used for accurate methotrexate measurement in the case of glucarpidase rescue.



-Xin Yi, PhD, DABCC, FACB, is a board-certified clinical chemist, currently serving as the Co-director of Clinical Chemistry at Houston Methodist Hospital in Houston, TX and an Assistant Professor of Clinical Pathology and Laboratory Medicine at Weill Cornell Medical College.

Microbiology Case Study: An Elderly Man with Abdominal Pain

Case History

The lab received two sets of admission blood cultures from an elderly man with a history of atrial fibrillation, aortic valve replacement six years ago, and idiopathic pancytopenia who presented with abdominal pain and symptoms of decompensated heart failure.

Lab Identification

At 59 hours, one aerobic bottle showed growth of a gram negative bacillus. The organism grew pure yellow-pigmented colonies on the blood and chocolate plates with no growth on the MacConkey plate.

Gram stain from blood agar plate.

The Verigene microarray was not able to identify the organism against 12 gram negative targets. The organism was identified by MALDI-TOF mass spectrometer as Brevundimonas vesicularis. The organism could not be grown for susceptibility testing.


B. vesicularis is an aerobic, glucose non-fermenting, spore non-forming, gram negative bacillus closely related to Pseudomonas species. It will demonstrate slow growth of yellow-pigmented colonies on chocolate and blood agar plates with variable growth on MacConkey agar plates. It has in the past been classified as Corynebacterium and Pseudomonas vesicularis. It has been identified globally in environmental sources such as soil, spring water, and healthcare related water containers. It has been identified as a community-acquired, and increasing a hospital-acquired, pathogen in all age groups, and particularly in immunocompromised patients [1, 2]. It has been most commonly reported as a cause of bacteremia, but has also been implicated as the causative agent in cases of arthritis, meningitis, endocarditis, peritonitis, and urinary tract infection [1]. Interesting in vitro studies have demonstrated that the presence of B. vescularis may facilitate the growth of Legionella [3].

Even in cases of the septicemia in immunocompromised patients the mortality rate from B. vesicularis is relatively low. Strains have demonstrated resistance to most forms of antibiotics though is most consistently susceptible to amikacin and piperacillin-tazobactam [1, 2].



  1. Shang ST, Chiu SK, Chan MC, Wang NC, Yang YS, Lin JC, Chang FY. Invasive Brevundimonas vesicularis bacteremia: Two case reports and review of the literature. J Microbiol Immun Inf. (2012) 45: 468-472.
  2. Zhang CC, Hsu HJ, Li CM. Brevundimonas vesicularis bacteremia resistant to trimethoprim-sulfamethoxazole and ceftazidime in a tertiary hospital in southern Taiwan. J Microbiol Immunol Infect. (2012) 45(6): 448-452.
  3. Koide M, Higa F, Tateyama M, Cash HL, Hokama A, Fujita J. Role of Brevundimonas vesicularis in supporting the growth of Legionella in nutrient-poor environments. New Microbiol. (2014) 1:33-39.


-Taylor Goller is a Pathology Student Fellow at University of Vermont Medical Center.


-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.

Hematopathology Case Study: What’s in Those Histiocytes?

Case history

A 50 year old female with a past medical history significant for Sjogren’s syndrome and ventricular tachycardia s/p ICD placement presented for a routine chest X-ray in which a 1.8 cm spiculated left upper lobe lung mass was identified. A subsequent PET scan revealed FDG avidity. Other Imaging revealed no lymphadenopathy. The patient is a non-smoker and has no other comorbidities. A core needle biopsy with fiducial placement was performed.


H&E 10x
H&E, 20x
H&E, 50x
Kappa ISH
Lambda ISH

Sections of lung core biopsy material show numerous histiocytes containing eosinophilic intracytoplasmic globular inclusions. An admixed population of plasma cells are seen which are present in aggregates along with mature appearing lymphocytes. The plasma cells also demonstrate globular inclusions within their cytoplasm.

By immunohistochemistry, CD3 highlights scattered mature T-cells while CD20 highlights B-cells present in focal aggregates. Numerous plasma cells are present and are positive for CD138, CD79a, BCL2, and MUM1. By in situ hybridization, plasma cells are greatly kappa predominant. IgG is positive in the majority of the plasma cells with only rare cells staining for IgA and IgM. CD68 is positive in the numerous histiocytes.

IGH gene rearrangement studies by PCR demonstrated was positive, indicating a clonal population.

Overall, the findings are consistent with a crystal-storing histiocytosis with an associated plasma cell neoplasm or low-grade B-cell lymphoproliferative disorder.

Following the diagnosis, the patient received stereotactic body radiation therapy given the localized findings.


In this case, the findings are morphologically consistent with crystal-storing histiocytosis (CSH), which is a rare lesion that is the result of intralysosomal accumulation of immunoglobulin. The immunoglobulin is stored as crystalline structures within histiocytes that occupy the vast majority of a mass forming lesion. Multiple sites can be involved, which include bone marrow, lymph nodes, liver, spleen, gastrointestinal tract, and kidney. Most often, the lesion is confined to a single site but occasional generalized forms with multiple organ involvement have been described. CSH is also often associated with B-cell lymphoproliferative disorders or plasma cell dyscrasias, but rarely are the result of chronic inflammatory conditions.

The assessment of CSH requires excellent staining to identify the quality of the histiocytes. As mentioned, CSH will show intracytoplasmic inclusions that are eosinophilic in nature. Mimickers of CSH include mycobacterial and fungal infections, mycobacterial spindle cell pseudotumor, malakoplakia, HLH, storage disorders such as Gaucher’s, as well as histiocytic lesions such as xanthogranuloma, Langerhans cell histiocytiosis, fibrous histiocytoma, Rosai Dorfman disease and rarely other eosinophilic tumors such as rhabdomyoma, granular cell tumor, and oncocytic neoplasms.1

A thorough review of the literature as well as a clinicopathologic study by Kanagal-Shamanna R et al revealed that the localized type of CSH was the dominant presentation in which over 90% of cases showed isolated masses. Per previous reviews, localized lesions were often found in the head and neck as well as lung.2 A study group in which 13 cases that showed CSH, 12 demonstrated an underlying lymphoma or plasmacytic neoplasm. Interestingly, in 5 of the cases, the histiocytic infiltrate was so prominent and dense that it obscured the underlying neoplasm. In these particular cases, immunohistochemistry and PCR were of great importance.

Although the majority of cases of CSH are the result of an underlying lymphoproliferative disorder or plasma cell neoplasm, rare cases of report inflammatory processes have been described, particularly in the setting of an immune mediated process such as rheumatoid arthritis or Crohn disease.

Overall, although a rare entity, it is important to be aware of CSH and its mimickers as this can be an elusive diagnosis to make, especially when the histiocytic infiltrate is dense.


  1. Kanagal-Shamanna R, et al. “Crystal-Storing Histiocytosis: A Clinicopathologic Study of 13 Cases,” Histopathology. 2016 March; 68(4): 482-491.
  2. Dogan S, Barnes L, Cruz-Vetrano WP “Crystal-storing histiocytosis: a report of a case, review of the literature (80 cases) and a proposed classification,” Head Neck Pathol. 2012; 6:11-120.



-Phillip Michaels, MD is a board certified anatomic and clinical pathologist who is a current hematopathology fellow at Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA. His research interests include molecular profiling of diffuse large B-cell lymphoma as well as pathology resident education, especially in hematopathology and molecular genetic pathology.

Microbiology Case Study: A 7 Month Old Female with Fever and Seizure-Like Episodes

Case History

A 7 month old female presented to the emergency department (ED) due to fever and seizure-like episodes. Her mother reported the child had been persistently febrile for 5 days (Tmax 103.9°F) with rhinorrhea, fussiness and decreased oral intake. The patient experienced 3 seizure-like episodes on the day of admission, which the mother described as periods of “shaking” with eyes rolling back. The child was unresponsive during these episodes, which lasted 1 to 2 minutes each. The child had been taken to her pediatrician the day prior to presentation to the ED where she was given a shot of ceftriaxone for presumed otitis media. The child received a chest x-ray, influenza testing, and blood and urine cultures were collected. She also had a lumbar puncture performed and the cerebral spinal fluid (CSF) was sent for chemistries, bacterial culture and polymerase chain reaction (PCR) testing for meningitis/encephalitis pathogens. She was started on IV ceftriaxone.

Laboratory Testing

The child’s white blood cell count from peripheral blood was 7.1 TH/cm2 and chest x-ray, urinalysis and flu testing were unremarkable. The CSF was clear and colorless with 7 WBC/cm2, glucose of 57 mg/dL and protein of 21 mg/dL. The cytospin Gram stain identified no organisms. The meningitis/encephalitis panel detected the presence of human herpesvirus 6 (HHV-6).


Human herpesvirus 6 is a member of the Herpesviridae family and was the sixth herpes virus identified. Structurally, HHV-6 possesses a double stranded DNA genome and is enveloped. Clinically, it is the etiologic agent of roseola infantum (exanthum subitum) in infants and toddlers. Primary infection occurs in early childhood and those infected can be asymptomatic or have a non-specific febrile illness while only the minority present with the characteristic red macular rash prominent on the trunk and extremities, lymphadenopathy and high fevers. HHV-6 is highly neurotropic and as such causes viral encephalitis with 5-15% of children experiencing febrile seizures as a result of this illness. HHV-6 is highly prevalent with a greater than ninety percent seropervalence rate. HHV-6 establishes latency in T lymphocytes and can reactivate & cause disease, especially in immunocompromised patients such as those recipients of stem cell or solid organ transplants.

Traditional laboratory methods of identification for HHV-6 were challenging as viral culture, while once the gold standard for active disease, is not practical for most labs and is no longer used in routine diagnostics. PCR from serum, plasma or CSF has become the preferred test as there are now FDA-cleared, commercial platforms that are easy to use, allow for rapid turnaround time and in the case of multiplex PCR panels, the ability to target multiple pathogens from one test. Serology, while helpful in the diagnosis of primary infections, may not be provide conclusive results in a timely manner and is of limited utility in reactivation. Other less commonly used methods include immunohistochemistry, in situ hybridization and electron microscopy.

The prognosis for patients infected with HHV-6 is generally good with self-limited illness not requiring treatment. Rarely, multi-organ involvement can occur and HHV-6 infection in immunosuppressed patients can be a major cause of morbidity and mortality. There is no antiviral therapy licensed for the treatment of reactivated disease in this setting, but approaches using ganciclovir and valganciclovir have been proposed.

In the case of our patient, her blood, urine and CSF cultures were negative and her antibiotics were stopped after cultures were no growth at 24 hours. She required no treatment other than supportive care with acetaminophen for fever control. Prior to discharge, she developed a fine rash on her face, the back of her neck and trunk that was characteristic of an HHV-6 rash. This case demonstrates the utility of multiplex PCR testing in providing rapid identification of pathogenic organisms allowing for real time diagnosis and the limiting of unnecessary treatment.



-Eric Tillotson, MD, is a second year Anatomic and Clinical Pathology resident at the University of Mississippi Medical Center.


-Lisa Stempak, MD, is an Assistant Professor of Pathology at the University of Mississippi Medical Center in Jackson, MS. She is certified by the American Board of Pathology in Anatomic and Clinical Pathology as well as Medical Microbiology. She is the director of the Microbiology and Serology Laboratories. Her interests include infectious disease histology, process and quality improvement and resident education.



Microbiology Case Study: A 56 Year Old Woman with Purulent Vaginal Discharge and Dysarthria

Case History

The lab received a purulent fluid from a frontal subdural empyema in a 56 year old woman with a several month history of sporadic bloody to purulent vaginal discharge and a two week history of severe headache, facial weakness, and recent dysarthria causing her to seek treatment. Pelvic exam and CT of the abdomen revealed a fungating cervical mass, later found to be adenocarcinoma, with possible fluid collection within the uterine cavity.

Lab Identification

Initial gram stain of the subdural fluid showed moderate neutrophils and no bacteria. The aerobic plate showed no growth at 48 hours. The thioglycollate broth grew “puffballs” containing long gram negative bacilli with tapered ends.


Anaerobic blood agar plate on day 9. Note: large white colonies are contamination.
Gram stain from anaerobic plate on day 9.

The anaerobic plate grew few grey colonies composed of similarly-shaped gram negative bacilli. MALDI-TOF mass spectrometer identified both colony morphologies as Fusobacterium nucleatum.


F. nucleatum is a gram negative, spore non-forming, asacchrolytic, slow-growing, obligate anaerobe that can fluoresce chartreuse under UV light. It is one of 14 species within the Fusobacterium genus and is further classified into 5 subspecies (nucleatum, animalis, fusiforme, vincentii, and polymorphum) which have different pathogenic profiles. It is commonly associated with the oral cavity, though it is unclear if it is ever a constituent of usual flora. Its main virulence factors are invasion of epithelial and endothelial cells, induction of host immune response, and adhesion to tissue through a variety of adhesins. The FadA adhesin interacts with the ubiquitous cell junctional cadherins leading to increased permeability of the epithelial and endothelial barrier. This interaction may be why F. nucleatum infections can be found in such diverse locations within the body and are often part of a polymicrobial infection [1, 2].

F. nucleatum is a constituent of oral plaque and is strongly associated with gingivitis and periodontitis. It is present in increased quantity with increasing severity of disease and in patients with a history of smoking or uncontrolled diabetes mellitus. It is a known pathogen in infections and abscesses of the head and neck, brain, lung, abdomen, blood, and pleura. It is also commonly found in placental and fetal tissues and strongly associated with a variety of obstetrical conditions including preterm birth, chorioamnionitis, and neonatal sepsis. It has been implicated in at least one case as the causative agent of stillbirth. Its prevalence in cord blood in cases of neonatal sepsis is equal to or greater than that of E. coli and Group B Strep. There is also a known association between F. nucleatum and colorectal cancer and IBD, with current research investigating whether the bacteria could play a role in pathogenesis. [1].

F. nucleatum is generally responsive to treatment with a range of antimicrobials, though there are reports of strains resistant to clindamycin and beta-lactamase-based resistance to ampicillin [2, 3].

The infectious disease clinician covering the present case suggested that the patient may have been transiently bacteremic due to her fungating gynecologic malignancy and suffered a minor head trauma causing a small subdural hemorrhage that seeded the bacteria in a sufficiently protected anaerobic environment.



  1. Han TW. Fusobacterium nucleatum: a commensal-turned pathogen. Curr Opin Microbiol. (2015) 23:141-147.
  2. Denes E, Barraud O. Fusobacterium nucleatum infections: clinical spectrum and bacteriological features of 78 cases. Infection (2016) 44:475-481.
  3. Veloo ACM, Seme K, Raanges E, Rurenga P, Singadji Z, Wekema-Mulder G, van Winkelhoff AJ. Antibiotic susceptibility profiles of oral pathogens. Intl J Antimicrob Agents. (2012) 40:450-454.


-Taylor Goller is a Pathology Student Fellow at University of Vermont Medical Center.


-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.