1
Q
LO1: Basics of purine metabolism
A
Purines are broken down to form hypo-xanthine and sequentially oxidised by xanthine oxidase to form urate.
2
Q
Clinical features of acute gout
A
- Rapid build up of paint
- “Exquisite pain”
- Affected joint red, hot, swollen
- Most common joint = 1st MTP joint of the big toe
- Management = Reduce inflammation (vs managing hyperuricaemia more for chronic gout) - impt differentiator
3
Q
Gout aetiology + epidemiology
A
- Crystal arthropathy - monosodium urate crystals
- Needle shaped crystals - sets off intensive inflammatory reactions
- Epidemiology
- Males 3% (post puberty except Lesch Nyhan)
- Females 0.5% (more common post menopause)
4
Q
Why do humans have issues with urate
A
In other animals, urate is then broken down to form allantoin by urease.
Allantoin is highly water soluble and freely excreted in the urine.
we do not have functional urease (while we do have the rudimentary gene)
- Urate is relatively insoluble
- Urate circulates in the bloodstream at concentrations just below it max solubility, meaning that it is constantly on the brink of precipitating out to form urate crystals.
Plasma concentrations of monosodium urate
- Men: 0.12-0.42 mmol/l
- Women: 0.12-0.36 mmol/l (one reason why women get less gout than men)
- Solubility at 37oC = 0.40mmol/l
- Solubility drops at cooler temperature and lower pH (more acidic)
5
Q
3 Key Principles of purine metabolism
A
- You can make purines by 2 ways: de novo synthesis (green box) or salvage mechanism aka recycling (blue box)
* De novo = difficult, inefficient, highly metabolically expensive, body only uses this if there is extremely high requirements of purines e.g. bone marrow due to high cellular division whereby salvage alone is insufficient
* Salvage = highly energy efficient, body predominantly uses this pathway - Rate limiting step in de novo purine synthesis is catalysed by enzyme PAT (PPRP Amido Transferase)
*
* PAT under feedback inhibition by outputs GMP and AMP (the left and right dotted arrows)
* PAT is also under feed forward effect whereby activity is stimulated by higher levels of PPRP (substrate)
* Break and accelerator example - HPRT/HGPRT = hypoxanthine-guanine phosphoribosyltransferase is the main enzyme that recycles partially catabolised purine and bring them back up the metabolic pathway (salvage pathway)
* Absolute deficient = Lesh Nyhan
* No HGPRT = no recycling of purines to GMP or IMP
* Lack of GMP/IMP = reduced negative inhibition of PAT
* De novo synthesis pathway goes into overdrive, excessive purine synthesis
* The massive loads of purines has no where else to go (because there is not corresponding need) and is broken down the purine pathway (IMP → Inosine → hypoxanthine → Xanthine → Urate)
* Additionally, lack of guanine recycling causes accumulation of PPRP (forward accelerator)
6
Q
Two types of gout
A
- Acute - Podagra (pod/foot aggravation)
- Chronic - Tophaceous (not acute pain but chronic deposition of urate crystals in soft tissue, tophi in earlobes and adjacent to joints- chalky, cottage cheese)
7
Q
Treatment acute gout (reduce inflammation)
A
- NSAIDS (1st line)
- Colchicine (2nd line, inhibit polymerisation of tubulin which in contact of gout 1. reduce cell turnover and 2. reduce motility of neutrophils to prevent neutrophils from participating in inflammation)
- Glucocorticoids
- DO NOT ATTEMPT TO MODIFY PLASMA URATE CONCENTRATION (reducing can paradoxically increase urate crystal formation)
8
Q
Treatment chronic gout or interval non-acute attacks (managing hyperuricaemia)
A
- Drink plenty water
- Reverse factors putting up urate (diuretics especially thiazide diuretics)
- Reduce synthesis with allopurinol (inhibit xanthine oxidase)
- Increase renal excretion with probenecid (uricosuric)
9
Q
Allopurinol cannot be given with ____ + why
A
- Do not give together with AZATHIOPRINE - steroid sparing agent, used to gently suppress bone marrow to act as immune suppressor, prodrug for 6-mercaptourine → thioinosinate which interfere with purine metabolism
- If given with allopurinol which is inhibitor of xanthine oxidase and given azathioprine (which makes purine and adds to purine pathway), you amplify the effects of azathioprine to toxic levels = shut down bone marrow and result in pancytopenia (cardinal medical sin - also do not give trimethoprim with methotrexate)
10
Q
Diagnosis of gout (3)
A
- Tap effusion
- View under polarised light
- Use red filter
Study birefringence
- birefringence = property of the crystal to rotate the axis of the polarised light
- Urate crystals = negatively birefringence (urate crystal = needle light = negative)
- Negative means it rotates 90 degrees to the filter (blue needle)
- Pyrophosphate (psuedogout) is blue in the axis of the red compensator (py = positive)
11
Q
Psuedogout
A
(the only other crystal arthropathy)
- Occurs in patients with osteoarthritis
- Pyrophosphate crystals
- Self-limiting 1-3 weeks
- Affects different joints (osteo joints)
- Positively birefringence, blue in line with axis of red compensator
12
Q
Diagnostic requirement for coeliac disease
A
endomysial antibodies and tissue transglutaminase antibodies
13
Q
Duodenal biopsy of pt with coeliac disease will show
A
On gluten rich diet showing villous atrophy
Off gluten showing normal villi
14
Q
MALToma associated with Coeliac found in the _______ and is B/T lymphocyte origin
A
MALToma associated with Coeliac found in the duodenal and is of T lymphocyte origin (Enteropathy Associated T-cell lymphoma)
15
Q
Treatment for essential thrombocytopenai
A
Treatment
- Aspirin - prevent thrombosis
- Anagrelide - inhibition of platelet function (SE palpitations and flushing)
- Hydroxycarbamide - antimetabolite, suppress other cells, mildly leukaemogenic
16
Q
What should you think of when you see leuco-erythroblastic blood film?
A
Bone marrow
Means there is infiltration
17
Q
What causes leuco-erythroblasti blood film?
A
- Root issue: bone marrow infiltration by
- Cancer
- Haemopoietic: leukaemia/lymphoma/myeloma
- Non-Haemopoieotic: breat/bronchus/prostate
- Severe infection
- Military TB
- Severe fungal infection
- Myelofibrosis
- Masive splenomegaly
- Dry tap on BM aspirate
- Cancer
18
Q
Morphological features of leuco-erythroblastic blood film
A
- Teardrop RBC
- Nucleated RBC
- Immature myeloid cells
19
Q
Fe deficiency is always due to ____ unless proven otherwise
A
OCCULT BLOOD LOSS
from GI cancers or urinary tract cancers
20
Q
Common distinguishing features of haemolysis of RBC
A
- Anaemia (though may be compensated)
- Reticulocytosis
- Raised bilirubin (unconjugated)
- Raised LDH (intracellular enzyme released into plasma when RBC lyse)
- Reduced haptoglobin (because haptoglobin binds to free haemoglobin in the blood released from lysed cell)
21
Q
Causes of inherited haemolytic anaemia
A
Think of the structure of RBC
Membrane:
- hereditary spherocytsis
- hereditary elliptocytosis
Enzyme:
- G6PD def
- pyruvate kinase def
- Pyrimidine-5’-nucleotidase def
Hb:
- Thalassaemia (number)
- Sickle cell disease (functional)
- unstable Hb variant
22
Q
Features that suggest this haemolytic anaemia is inherited
A
Are the common lab features of all Haemolytic anaemia present?
Ethnic background (why are these anaemias so common worldwide?)
Is there a family history/lifelong history with first presentations in childhood/recurrent episodes?
Pigment gallstones?
23
Q
What is one test to distinguish between immune and non-immune causes of haemolytic anaemia
A
Direct Antiglobulin (DAT or Coombs test)
24
Q
Autoimmune and non-immune causes of acquired haemolytic anaemia
A
Auto-immune causes of acquired haemolytic anaemia
- Spherocytes, DAT+ve
- Cancer of immune system: lymphoma
- Disease of immune system: SLE
- Infection affecting the immune system: EBV, HIV
Non-immune causes of acquired haemolytic anaemia
- Infection (malaria)
- MAHA
- Red cell fragments
- Low platelets
- Bleeding/DIC
- Underlying adenocarcinoma
25
Haemolytic aneamis associated with systemic disorders
Associated systemic disorder
Cancer of immune system: lymphoma
Disease of the immune system: SLE
Infection (disturbing the immune system)
26
Explain how adenocarcinomas or DIC causes acquired, non-immune haemolytic anaemia
1. Consume platelets (in DIC)
2. Coagulation activation (cancer)
3. Formation of fibrin strands - cheese strings
4. Red cells pushed through this mesh at high pressure due to BP
5. SHEEEEEAAAARRRR - red cell fragmentation (microangopathy)
6. Haemolysis
27
List the primary and secondary causes of TRUE polycythaemia
primary (low EPO)
* Polycythaemia vera - clonal proliferation of red cells from acquired mutations in JAK2
Secondary (high EPO)
* Appropriate causes - high altitude, hypoxia, cyanotic heart disease, high affinity haemoglobin
* Inappropriate - liver cancer, renal disease (EPO tumours), lung cancer
28
Female aged 39 treated breast cancer 4 years previously
- recent onset jaundice and hepatomegaly
- GP bloods
- Hb 87g/l
- Reticulocyte 15x10^9/L (20-92)
- Bilirubin 50 micromol/l conjugated
DAT negative
Blood film
- leuco-erythroblastic anaemia
- leuco-erythroblastic anaemia think bone marrow
Infiltrates from cancer or infections
In this lady probably her breast cancer mets to liver and bone marrow
29
Investigation of raised white cell from a blood test
What do you want to do/investigate?
Ask for blood film - are the cells mature or immature? And there features
What lineage - specific e.g. granulocytes or all (granulocytes + lymphocytes)
How high?
30
Causes of neutrophilia
- infection (reactive)
- cancer (myeloproliferative disorders, leukaemia disorder)
- tissue inflammation (e.g. pancreatitis, colitis)
- underlying neoplasia
- corticosteroids
31
What infections classically do not produce neutrophilia
brucella, typhoid, many viral infections.
32
What features of the neutrophil on the blood film and pt would suggest this is a reactive neutrophilia?
Presence bands, toxic granulation (vacuoles), and clinical signs of infection/inflammation (pyrexia, abscess, raised X? protein
33
What features on a blood film suggest malignant increase in WBC?
Neutrophilia, basophilia plus immature cells myelocytes, and splenomegaly. Suggest a myeloproliferative (CML)
Neutropenia plus Myeloblasts (AML)
34
Causes of reactive eosinophilia?
Parasitic infestation
allergic diseases e.g. asthma, rheumatoid, polyarteritis, pulmonary eosinophilia.
Underlying Neoplasms, esp. Hodgkin’s, T-cell NHL (reactive eosinophilia)
- release of IL5 from neoplasms causing einsophilia
Drugs (reaction erythema mutiforme)
35
Chronic Eosinophilic leukaemia
Eosinophils part of the “clone”
| FIP1L1-PDGFRa Fusion gene
36
Causes of monocytosis
Monocytosis is generally rare but seen in certain chronic infections and primary haematological disorders
TB, brucella, typhoid
Viral; CMV, varicella zoster
sarcoidosis
chronic myelomonocytic leukaemia (MDS)
37
Interpreting a lymphocytosis
Determine if this primary (cancer) or secondary (benign)
- primary = monoclonal
- secondary = polyclonal, reactive to infection or inflammation
Clinical
Symptoms suggestive of infection or lymphoma
Massive lymphadenopathy or splenomegaly
FBC
Degree of lymphocytosis
- Modest lymphocytosis likely reactive
- Massive lymphocytosis more likely primary
Light microscopy/ morphology
Mature cells (reactive or CLL/NHL) or primitive lymphoblasts (ALL)
Flow cytometry
Lineage; B or T cells
Stage of differentiation
Molecular genetics
Rearranged: T cell receptor or Immunoglobulin gene
38
Causes of reactive lymphocytosis
infection and inflammation
Infection
EBV, CMV, Toxoplasma
infectious hepatitis, rubella, herpes infections
autoimmune disorders
sarcoidosis
39
Blood film of CLL
Small lymphocytosis
| Smear cells
40
CD19 marks a
B lymphocyte
41
CD3 and CD8 marks
ALL T cells
42
Tdt marks
A lymphoid stem cell
43
45 year old male
3 week history of sore throat
Recent episode of shingles
EBV IgG serology positive
FBC
Lymphocytes 12x109/L (raised)
Neutrophils 7x109/L (normal range)
Film: reactive lymphocytes no abnormal cells
Flow cytometry shows:
CD19 - 55++% CD20 - 69++%
B cell: 87++% kappa, 0% lambda
CD5/CD19 - 5%
Diagnosis?
Mature B cell CLL
Do to get tricked by the EBV IgG+ because IgG (suggest past infection not active infection)
44
Two principal mechanisms of anaemia
Decreased production
-BM infiltration, leucoerythroblastic film
Increased destruction
- Lab markers of haemolysis (retics, LDH, Bilirubin)
- Immune (spherocytes and DAT) lymphoid tumours
- Microangiopathic (red cell fragments) adenocarcinoma
45
In the context of PNH, what is the role of GPI in red cell function? Do PNH have more and less GPI?
* GPI in the context of RBC is important for complement regulation such that RBC are protected against complement destruction
* Hence def of GPI seen in PNH result in complement mediated red cell destruction
46
How do you classically test for hereditary spherocytes? What has that test now been superseded by?
Hallmark: Increased sensitivity to lysis in hypotonic saline (osmotic fragility test) - superseded by simpler diagnostic test of reduced binding of dye oesin-5-maleimide (flow cyto, reduced mean cell fluorescence)
47
What is the inheritance pattern for hereditary spherocytosis?
Majority AD
| 25% recessive and a little de novo
48
What is the link between hereditary ellipocytosis and hereditary pyropoikilocytosis?
Hereditary pyropoikilocytosis is the more severe form of hereditary ellipocytosis where the pt is homozygote
In hereditary elliptocytosis the pt is usually asymptomatic and do not have anaemia
49
G6PD def is a cause of inherited haemolytic anaemia. What does G6PD actually do?
* G6PD catalyses first step in pentose phosphate pathway - main function to generate NADPH to maintain intracellular glutathione (GSH)
GSH is impt for combating oxidative stress
* Hence def = lack of NADPH and vulnerable to oxi stress
Hence G6PD HA is triggered by oxidative stress, infections and fava beans
50
Characteristics of G6PD blood film - buzzwords
Nucleated RBC
Bite cells
Hemighost
Contracted cells
51
Which key clotting factor activates both factors V and VIII, and also activates protein C?
Thrombin
52
How do you tell the difference between petechiae, purpora and ecchymosis?
Purpura measure 0.3–1 cm (3–10 mm), whereas petechiae measure less than 3 mm, and ecchymoses greater than 1 cm.
53
What important study is conducted in all newly diagnosed AML pts? and why is this study done?
Cytogenetic studies is done in all AML pts. Molecular studies are done in selected pts.
Why?
Prognostic value + helps select treatment
Good prognostic e.g. Inv(16)= treat with medication and no bone marrow transplant
Bad prognostic e.g. del5/7, complex karyotype = achieve remission with meds and push for bone marrow transplant
54
Causes of relative polycythaemia
Due to reduced plasma volume
- Alcohol
- Obesity
- Diuretics
55
normal hct
0.41-0.53
56
normal hb
135-175 g/l
57
3 signs of portal hypertension
* Visible veins - huge veins, large risk of bleeding and death
* Alcoholic + portal hypertension start bleeding/vomitting blood = EMERGENCY EMERGENCY
* Splenomegaly - portal veins come from the splenic veins. because there is portal hypertension hence it backlogs into the spleen.
* Ascites
58
Example of antibiotics that causes marrow failure
Chloramphenicol
| Sulphonamide
59
Examples of diuretics and thyroid medication that causes bone marrow failure
Thiazides and Carbimazole
60
DDx of pancytopenia + hypo cellular marrow
Pancytopenia + hypocellular marrow is the definition of aplastic anaemia
Therefore qn is what is ddx for aplastic anaemia
* Hypoplastic MDS/AML
* Hypo cellular ALL
* Hairy cell leukaemia
* Mycobacterial infection
* Anorexia nervosa
* Idiopathic thrombocytopenia purport (ITP)
61
This haem cancer is the MOST associated with DIC
APML
AML in generally but in particular APML
62
DDx for Auer rods
AML (most types)
but also CMML (which is a type of AML to be fair)
And MDS, refractory anaemia with excess blast 2 (REAB-2)
Also APML which is packed full of granules
63
Treatment for t(15:17) haem cancer
t(15:17) is PML-RARA mutation found specifically in APML
Treatment is ATRA (all-trans retinitis acid) in addition to chemo
ATRA forces the cells to differentiate
64
Treatment for t(15:17) haem cancer
t(15:17) is PML-RARA mutation found specifically in APML
Treatment is ATRA (all-trans retinoid acid) + chemo
ATRA forces the cells to differentiate
65
Name a vascular abnormality that could cause gangrene of fingers
* Raynaud's phenomenon or chronic peripheral vascular disease
* Could be diabetes with arthersclerosis
* Cold RBC disease that precipitates/agglutinats in the cold
66
* Write down three abnormalities of the blood that could be responsible for gangrene of the fingers
* PCV - leading to sluggish blood.
* Cryoglobulinaemia - proteins precipitate in the cold leading to reduced circulation and vascular thrombosis.
* DIC
67
Elderly man presenting with severe bruising near the elbows. * On this day his platelet count was 13x10^9/L
* * A week earlier it had been 3 with a normal Hb and WBC.
diagnosis?
* Probably ITP given none of the other lineages appear to be affected.
* Consider drug induced and DIC as the next causes.
* TTP likely will have anaemia and red cell fragments
unlikely to be malignancy as normal Hb and WBC
68
A 69yr old man in ICU
* He has extensive atheromatous disease and diabetes mellitus
* He has had an abdominal aortic aneurysm replaced by a graft and has had a stormy post-operative course with
* Sepsis
* Acute renal failure
* Respiratory impairment
* His FBC shows:
* WBC 37.5 × 109/l (high)
* Neutrophil count 35 × 109/l (high)
* Lymphocyte count 0.8 × 109/l (low)
* Monocyte count 1.2 × 109/l
* Myelocytes and metamyelocytes 0.5 × 109/l (shouldn’t be in the peripheral blood but not blasts)
* Hb 110 g/l (anaemic)
* MCV 89 fl
* Platelet count 514 × 109/l (high)
* Film comments
* Toxic granulation and vacuolation
* Left shift
* Rouleaux
Diagnosis?
1. Chronic myeloid leukaemia
2. Normal for age and gender
3. Reactive neutrophilia
4. Laboratory error
5. Acute myeloid leukaemia
3. Reactive neutrophilia
* Toxic granulation, vacuolation and rouleaux formation indicate the presence of more acute phase proteins, therefore reactive.
* No blast cells present therefore it can't be AML
69
Blood film abnormality with pernicious anaemia
Hypersegmented neutrophils
70
Haematological complications of RA
* Anaemia of chronic disease
* IDA resulting from use of NSAIDs
* Neutropenia or thrombocytopenia from drug toxicity
* Amyloidosis
* Felty's syndrome: neutropenia, RA and splenomegaly.
* Increased ESR independent of inflammation
71
* Osteomyelitis is marginally more common in children than septic arthritis
Note
* Fever is often present and the WBC is often increased in osteomyelitis but not invariably
* There is a history of trauma in 35% so this should not deflect you from this diagnosis because children and trauma is common
* The CRP is normal in only 2% of cases
72
Antiphospholipid syndrome - do you increase aPTT or PT?
| DIC increase aptt or pt?
Antiphospholipid syndrome/ lupus anticoagulants increase aPTT
DIC increase BOTH aptt and Pt
73
What is the underlying defect in TTP?
* The underlying defect in thrombotic thrombocytopenic purpura is a deficiency of a plasma protein called von Willebrand factor cleaving protease (or ADAMTS13)
* The deficiency is autoimmune in origin
* The low levels of the protease lead to high levels of very large multimers of vWF, which cause platelet thrombi to form
* The widespread platelet thrombi are responsible for the clinicopathological features
You get low platelets and MAHA
74
What are the risks of hyposplenism?
| What is the management of hyposplenism
* Overwhelming bacterial sepsis (particularly pneumococcal, meningococcal or Haemophilus influenzae)
* Fatal malaria (warn)
* Fatal Capnocytophaga canimorsus infection (warn about dog bites)
* Capnocytophaga canimorsus is a fastidious, slow-growing Gram-negative rod of the genus Capnocytophaga.
* It is a commensal bacterium in the normal gingival flora of canine and feline species. Transmission may occur through bites, licks, or even close proximity with animals.
* C. canimorsus generally has low virulence in healthy individuals, but has been observed to cause severe illness in persons with pre-existing conditions.
* Penicillin G is the drug of choice, although there have been some isolates found to show resistance.
* C. canimorsus is susceptible to ampicillin, third generation cephalosporins, tetracyclines, clindamycin, and chloramphenicol. It has shown resistance to gentamicin. Treatment is recommended for a minimum of three weeks
Management of hyposplenism
* Vaccinate for pneumococcus, meningococcus type C and H influenza
* Vaccinate against influenza (under UK guidelines)
* Prescribe life-long penicillin
* Erythromycin if allergic to penicillin
* Advise the patient on
* Dog bites
* Travel to malaria zones
* Prompt treatment of infection
* Issue a splenectomy card and information sheet.
75
Pathophysiology of anaemic of chronic disease
* Reduction in red cell lifespan
* Cytokine release
* IFNg, IL1 and TNF
* Reduced proliferation of erythroid precursors
* Suppression of endogenous erythropoietin production
* Impaired iron utilisation
76
Microcytic anaemia - TAILS
| *
* Thalasseamia
* ACD
* Iron
* Lead
* Sideroblasts
77
Flow murmur in anaemia?
Ejection systolic loudest over apex
78
FAT RBC
Fetus
Antifolates
Thyroid
Reticulocytosis
B12 or folate deficiency
Cirrhosis (alcohol excess or liver disease)
Myelodysplastic syndromes
79
When advising oral Fe tables, warn about these 4 SE
Nausea
Abdo discomfort
Diarrhoea/constipation
Black stools
80
What if you gave folate to a B12 deficiency anaemia?
The flat acid will exacerbate the neuropathy of B12 deficiency. Hence DO NOT give folate when cause of macrocytic anaemia is unknown
81
Treatment for multiple myeloma
1. Steroids
2. Mephalan chemo
3. Proteasome inhibitors - Bortezomib which causes mid folded protein to build up to toxic levels and kill myeloma cells
4. Thalidomide, Lenalidomide which are toxic to lymphocytes
5. HST
82
Fanconi syndrome v Fanconi anaemia
Fanconi syndrome is a complication of multiple myeloma dx in the kidneys
- the AL amyloid deposits causes proximal tubule necrosis
- which leads to FANCONI SYNDROME where by glucose, amino acid and bicarb is NOT reabsorbed in the proximal tubules
Fanconi anaemia is a congenital cause of aplastic anaemia
83
First line treatment drug for CLL if p53 deletion
| Drug is p53 negative
Alemtuzumab
If p53 negative CLL then chlorambucil or clinical trials
Sera's MBBS
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