A 5-year-old previously healthy boy presents to the ED with diffuse petechiae. His mother states he had a viral respiratory illness 2 weeks ago but is now well. He has a normal physical examination. His blood film shows an isolated thrombocytopaenia with a platelet count of 8 x 109 /L.
Which ONE of the following is TRUE?
Answer: D: This child most likely has idiopathic thrombocytopaenic purpura (ITP); the result of thrombocytopaenia caused by immune destruction of platelets, often precipitated by intercurrent viral infections. Acute ITP is more common in young children and typically resolves spontaneously within 2–3 months, independent of any treatment. Chronic ITP is more common in adults, usually lasts more than 3 months and rarely remits spontaneously or with treatment.
The treatment of childhood ITP is controversial. There is no consensus as to whether ‘watchful waiting’ or pharmacologic intervention is most appropriate. Both the American Society of Hematology and British Society of Haematology have published guidelines for the management of ITP in children based on expert opinions and observational studies. The majority of children will not require treatment, as serious bleeding is rare. The risk of bleeding in ITP is lower for any given platelet count compared with other conditions and even pronounced skin purpura and bruising do not indicate a serious bleeding risk on their own. The British Society of Haematology guidelines currently recommend that that children be classified clinically and not by platelet count as even children with severe thrombocytopaenia (<10 × 109 /L) usually have ‘mild’ clinical symptoms.
Treatment, if indicated, is employed to promote platelet recovery and include corticosteroids, intravenous immunoglobulins (IVIg) and anti-Rh(D) immunoglobulin. Platelet transfusions are of no value in the management of ITP as platelets will be rapidly consumed by circulating antiplatelet antibodies. Current treatment recommendations from the British guidelines:
Regardless of whether pharmacologic therapy is used, restriction of activity should be recommended in all children with ITP. In addition, medications with antiplatelet activity, including the nonsteroidal antiinflammatory drugs, should be avoided.
References:
Regarding bleeding disorders, which ONE of the following statements is TRUE?
Answer: C: Abnormal bleeding is usually due to platelet deficiency or dysfunction, clotting factor deficiency, or a combination. Bleeding related to platelets presents with petechiae and mucosal bleeding that manifests as easy bruising, gingival bleeding, epistaxis, haematuria, gastrointestinal bleeding or heavy menses. Conversely, patients with spontaneous deep bruises, haemarthrosis, retroperitoneal bleeding, or intracranial bleeding are more likely to have a coagulation deficiency (i.e. haemophilia A and B).
Haemophilia A is a disorder due to deficiency in factor VIII, whereas haemophilia B is due to a deficiency in factor IX. Haemophilia A and B are clinically indistinguishable from each other. In patients with haemophilia, the prothrombin time (PT), which measures the extrinsic pathway, will be normal and the aPPT, which measures the intrinsic coagulation cascade, will be abnormal.
Von Willebrand’s factor (vWD) is the most common congenital bleeding disorder. Von Willebrand’s factor (vWF) is a cofactor for platelet adhesion as well as the carrier protein for factor VIII. Patients with vWD may present with features of both platelet and clotting factor dysfunction. Skin and mucosal bleeding symptoms are common. Haemarthrosis is not typical unless severe disease is present. Common abnormalities seen in vWD include prolonged bleeding time, low or normal vWF antigen and low vWF activity. The PT should be normal and about half of patients will have mildly prolonged aPTT.
Reference:
A 45-year-old female presents with fever. She is known to have breast carcinoma and has recently received chemotherapy.
Which ONE of the following is MOST correct?
Answer: D: Fever in cancer patients are defined as a single oral temperature ≥ 38.3°C, or an elevation of 38°C on at least 2 occasions or persisting >1 hour. All patients presenting with fever following chemotherapy should be assumed neutropenic until proven otherwise. Although rectal measurement most accurately reflects core body temperature, the theoretical risk of bacterial translocation during the procedure of inserting the thermometer into the anus is not recommended in these patients, and therefore oral or axillary measurements are preferred. Most fevers (55–70%) occurring in cancer patients have an infectious origin. Other causes include inflammation, transfusions, antineoplastics, antimicrobials and tumour necrosis.
Regarding febrile neutropenia in cancer patients, which ONE of the following is TRUE?
Answer: B: Approximately 85% of the initial pathogens are bacterial. Gram-negative bacilli, particularly Pseudomonas aeruginosa, used to be the most common pathogens found in the blood of febrile neutropenic patients until the 1980s. However, the administration of prophylactic antibiotics primarily active against gram-negative pathogens during chemotherapy, the widespread use of indwelling intravascular devices and newer chemotherapy regimens have lead to an increase in gram-positive pathogens and currently grampositive bacteria account for 60–70% of microbiologically confirmed infections in these patients. Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus epidermidis are the predominant gram-positive organisms. Once believed to be a contaminant, S. epidermidis has arisen as a major pathogen. Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae remain the most common gram-negative pathogens. Fungal, viral and parasitic infections are also important primary and secondary complications.
Vascular access can be challenging in patients receiving chemotherapy. Therefore, indwelling vascular catheters should be retained as far as possible. Even when catheter infection is suspected, the infection can be successfully treated in most cases without removing the catheter. The collection of a blood culture from vascular catheter lumen in addition to peripheral blood cultures may further assist in the diagnosis of clinically relevant catheter-related blood stream infections (CRBSI) by allowing the time necessary for blood culture from the peripheral vein to become positive to be compared with the time until blood culture from a central venous catheter becomes positive. A differential time to positivity of ≥120 minutes has been shown to be predictive of CRBSI. This approach is particularly useful in patients in whom catheter retention is desirable. Removal of the line is indicated in the context of tunnel infections, persistent bacteraemia despite adequate treatment, atypical mycobacteria infection and candidaemia. Vancomycin should be added when infection of the line is suspected and should be administered through the line when possible.
Regarding tumour lysis syndrome, which ONE of the following is TRUE?
Answer: B: Tumour lysis syndrome (TLS) is a metabolic crisis that arises from massive cell death with release of cellular contents in the circulation. It is associated with either a rapid growing tumour, or after chemotherapy or radiotherapy. It most commonly occurs with haematologic malignancies because of rapid growth rates and cell turnover, bulky tumour mass and high sensitivity to antineoplastic agents. The resultant electrolyte abnormalities include hyperkalaemia, hyperuricaemia, hyperphosphotaemia and hypocalcaemia. Malignant cells can contain up to four times the amount of phosphorous than normal cells, and with the abrupt release into the circulation may produce a significant drop in calcium. Lifethreatening complications, including arrhythmia and seizures, arise from electrolyte abnormalities, whereas renal failure is a common sequel from uric acid precipitation in the renal tubules.
Treatment is aimed at correction of electrolyte abnormalities and prevention of renal failure. Treatment of hyperkalaemia is identical to other causes of hyperkalaemia. However, administration of calcium is generally avoided unless there is evidence of cardiovascular instability (ventricular arrhythmia or widened QRS) or neuromuscular irritability (seizures), as it may cause metastatic precipitation of calcium phosphate. Aggressive intravenous fluid hydration is the single most important intervention. Not only does it help to correct electrolyte abnormalities by diluting extracellular fluid, but it also increases the intravascular volume with resultant improved renal flow and urine output. This counteracts precipitation of uric acid and calcium phosphate crystals in distal nephrons. The use of furosemide or mannitol for osmotic diuresis has not proven to be beneficial as first-line therapy. Instead, diuretics should be reserved for well-hydrated patients with insufficient diuresis, and furosemide alone should be considered for normovolaemic patients with hyperkalaemia or for the patients with evidence of fluid overload. Allopurinol is usually given because it inhibits the synthesis of new uric acid, but it has no effect on existing uric acid levels. Therefore, the effect is only seen after 48–72 hours. Haemodialysis should be considered if TLS is refractory to the above measures. The prognosis is good in the absence of renal failure.
Click to expand