List I - Core Conditions Flashcards
What is macrocytosis?
- MCV >96fL
What is a megaloblast?
- A cell in which nuclear maturation delayed compared to cytoplasm (occurs with B12 and folate deficiency as both are required for DNA synethesis)
How is folate absorbed / used in the body?
- Green vegetables, nuts, yeast, liver
- Synthesized by gut bacteria
- Absorbed by duodenum/proximal jejunum
- Body stores for at least 4 months
How is B12 absorbed / used in the body?
- Meat, fish, dairy products (not plants)
- Require 2mcg/day
- B12 is protein bound so released during digestion
- Binds to intrinsic factor in the stomach
- This complex is absorbed in the terminal ileum
- Body stores last 4 years
What is macrocytosis caused by?
- Megaloblastic anaemia
- B12 deficiency (pernicious anaemia - 5% but most common cause in the West), folate deficiency, cytotoxic drugs
- Non-megaloblastic anaemia
- Alcoholism (often without accompanying anaemia), reticolocytosis (e.g. haemolysis), liver disease, hypothyroidism, pregnancy, cytotoxic drugs
- Other haematological disease
- Myelodysplasia, myeloma, myeloproliferative disorders, aplastic anaemia
What are the causes of folate deficiency?
- Poor diet - poverty, alcoholics, elderly
- Increased demand - pregnancy, increased turnover (haemolysis, malignancy, inflammatory, renal dialysis)
- Malabsorption - coeliac disease, tropical sprue
- Others - drugs, alcohol, phenytoin/valproate, methotrexate, trimethoprim
What are the causes of B12 deficiency?
- Poor diet - vegan
- Malabsorption - stomach (lack of intrinsic factor): pernicious anaemia (autoimmune atrophic gastritis - achlorydia, lack of intrinsic factor secretion), post gastrectomy, terminal ileum: ileal resection, Crohn’s disease, bacterial overgrowth, tropical sprue, tapeworm
- Congenital - abnormalities in metabolism
What are the risk factors for pernicious anaemia?
- Other autoimmune conditions - (thyroid 25%. vitiligo, Addisons, hypoparathyroidism)
How common is macrocytosis / pernicious anaemia?
- Macrocytosis - common
* Pernicious anaemia - 1:1000, F:M 1/6:1, >40 years usually, increased incidence in blood group A
What is the pathophysiology of deficiency in folate / B12?
- Folate deficiency - maternal deficiency can cause neural tube defects
- B12 deficiency - impairs synthesis of thymidine (DNA) is impaired so reduced RBC production
- Subacute combined degeneration of the spinal cord (B12 deficiency) - combined symmetrical dorsal column loss (sensory/LMN signs) and symmetrical corticospinal tract loss (motor/UMN signs) but NB pain/temperature usually normal as spinothalamic tract often preserved
- Myelodysplasia - oval macrocytes with anisocytosis and poikilocytosis and small fragmented cells (schistocytes)
What are the symptoms and signs of macrocytic anaemia?
- Generally similar to IDA
- Signs (B12 deficiency)
- General - lemon tinge to skin from both anaemia pallor and haemolytic jaundice), glossitis (beefy red, sore tongue), angular cheilosis (aka stomatitis)
- Psychiatric - irritability, depression, psychosis, dementia,
- Neurological - paraesthesiae, peripheral neuropathy
- Subacute combined degeneration of the spinal cord (SACDS) - insidious onset, first joint position/vibration affected (ataxic gait: falls at night) - stiffness/weakness if untreated (classic triad of: extensor plantar response from UMN loss, absent knee jerks from LMN loss, absent ankle jerks from LMN loss)
What are the differentials for macrocytic anaemia?
Other causes of glossitis:
- Iron/zinc deficiency
- Pellagra
- Contact dermatitis/food intolerance
- Crohn’s
- Coeliac
- Drugs (minocycline, clarithromycin, some ACEi’s)
- Alcoholism
- Tongue TB (ulcers, fissures, tuberculoma, diffuse glossitis)
What are the appropriate blood investigations for macrocytic anaemia?
- Bloods - FBC (low Hb, high MCV, severe pernicious anaemia also low WCC, low platelets) should normalise within a week with therapy
- Serum B12 and folate (or red cell folate - more reliable indicator of folate status as serum folate only reflects recent intake), reticulocytes (low or normal in pernicious anaemia)
- Blood film - B12/folate deficiency (hypersegmented >5 segments - neutrophil polymorphs), liver disease (target cells)
- U and E’s - observed for low K+ as therapy becomes established
- LFT including GGT
- TFT
What are the special tests for macrocytic anaemia?
- Bone marrow biopsy if cause not revealed from blood tests
- Megaloblastic - B12/folate deficiencies
- Normoblastic - liver disease, hypothyroidism
- Abnormal erythropoiesis - sideroblastic anaemia, leukaemia, aplastic anaemia
- Increased erythropoiesis (haemolysis)
- Pernicious anaemia screen - parietal cell Abs (90%), intrinsic factor Abs
- Small bowel biopsy - to look for small bowel malabsorption (if <40 years)
What is the conservative approach to management of macrocytic anaemia?
- Lifestyle - improve dietary intake
What is the medical approach to management of macrocytic anaemia?
- Treat the cause - injections if malabsorption
- Oral supplements - folic acid 5mg/24h po for 4 months plus either cyanocobalamin (B12) 50-150mcg/24h po between meals (if folate deficiency and low B12) - NB giving folic acid in the presence of low B12 can precipitate SADC, or if B12 deficiency due to poor diet - leave out the folic acid - or hydroxycobalamin (B12) 1 mg/48 h IM (for 2 weeks if very ill with folate deficiency - e.g. CCF or for 2 weeks then maintained at 1mg IM every 3 weeks for life if pernicious anaemia and having sent the blood tests off)
- NB - improvement by transient increased MCV - due to reticulocytosis - after 4-5 days, additional iron may be needed
- Blood transfusions - rarely needed (indicated if severely symptomatic or Hb < 7-8)
What are the complications of macrocytic anaemia?
- Risk of pernicious anaemia - increase x 3 of gastric cancer, irreversible CNS complications (as for simple B12 deficiency)
- Prognosis - oral supplements improve peripheral neuropathy in 3-6 months (little effect on cord signs), earlier treatment = better prognosis
How is macrocytic anaemia prevented?
- Pregnancy
- Folate supplementation 400mcg/24 po (from conception until at least the last 12 weeks - to prevent spina bifida as well as anaemia)
- Women at higher risk of conceiving a child with a NTD should take 5mg of folic acid from before conception until the 12th week of pregnancy
- Women are considered higher risk if the any of the following apply:
- Either partner has a NTD, previous pregnancy affected by NTD, or FH NTD
- Woman is taking anti-epileptic drugs or has coeliac disease, diabetes, or thalassaemia trait
- Woman is obese (BMI 30 kg/m2 or more)
- Cognition - if borderline folate deficiency (shown by increase in homocysteine), folic acid 800mcg/24hrs po for 3 years may benefit cognition
What is haemolysis?
- Premature breakdown of RBC’s before normal life span of 120 days
What is haemolytic anaemia?
- When bone marrow cannot compensate for haemolysis
- Intra-vascular - within circulation
- Extra-vascular - within reticulo-endothelial system (liver, spleen, bone marrow)
What are the acquired causes of haemolytic anaemia?
- Drug induced - penicillin/quinine
- Auto-immune - occuring at body temperature, IgG mediated, splenic phagocytes, cold: occurring when cold, IgM mediated
- Paroxysmal cold Hb uria - with viruses/syphilis
- Acute transfusion reaction
- Haemolysis of newborn
- Microangiopathic haemolytic anaemia (MHA)
- Haemolytic uraemic syndrome - e.coli infection, deficiency of complement factor H, triad of acute renal failure, MHA and thrombocytopenia
- Thrombotic thrombocytopenic purpura - TTP: red cell fragments in blood, thrombocytopenia, neurological abnormalities, renal impairment, fever
- DIC
- Pre-eclampsia
- Mechanical heart valves - shearing
- Infection - malaria, viruses/syphilis
- Paraoxysmal nocturnal Hb-uria
What are the inherited causes of haemolytic anaemia?
- G6PD - x-linked, African/Mediterranean/Middle Eastern, needed to maintain glutathione (protects RBC’s against oxidative injury), neonatal jaundice, triggered by sulphonamides/aspirin/fava beans/henna, pyruvate kinase deficiency
- Autosomal recessive - reduced ATP production causes short RBC survival, childhood jaundice/anaemia and splenomegaly
- Hereditary spherocytosis - autosomal dominant, membrane dysfunction (makes them rounder, less pliable) become stuck in spleen/haemolysed, childhood jaundice/splenomegally
- Sickle cell anaemia
- Thalassaemia
Triggers - infection
What is the pathophysiology of haemolytic anaemia?
- Occurs either intravascular (in the circulation) or extravascular (in reticuloendothelial system: macrophages of liver, spleen, bone marrow)
- Sickle cell anaemia - life span as short as 5 days
What are the symptoms of haemolytic anaemia?
- Asymptomatic
- SOB
- Lethargy
- Pallor
- Dark urine
- Jaundice
PMH - previous anaemia
DH - medications
FH - Gilbert’s syndrome, ethinicity
SH - recent travel - malaria
What are the signs of haemolytic anaemia?
- Jaundice
- Pallor
- Splenomegaly (extravascular)
- Hepatomegaly
- Gallstones (pigmented from increased bilirubin)
- Leg ulcers (poor blood flow)
What are the differentials / how is diagnosis of haemolytic anaemia made?
Consider what is happening? - what could the cause be?
- Increased RBC breakdown - low Hb, increased MCV, increased unconjugated bilirubin, increased urinary urobilinogen (as no urinary conjugated bilirubin), increased LDH (released from RBC’s)
- Increased RBC production - high reticulocytes, causes high MCV, polychromasia (RBC’s of different ages stain differently)
- Mainly extravascular or intravascular
- Extravascular - splenic hypertrophy/splenomegaly
- Intravascular - increase in free plasma Hb (released from RBC’s), methaemalbuminaemia (haem combined to albumin), low plasma haptoglobin (as mops up free Hb, removed by liver), Hb-uria (red brown urine, in absence of RBC’s), haemosiderinuria (when haptoglobulin-binding capacity exceeded
What are the appropriate blood investigations for haemolytic anaemia?
- FBC (low Hb, high MCV, low platelets: HUS, increased reticulocytes)
- LFT (increase unconjugated bilirubin)
- LDL (increase as released from RBC’s)
- Haptoglobin (increase)
Blood film
- Hypochromic/microcytic (thalassaemia)
- Sickle cell (SCA)
- Schistocytes (MHA)
- Abnormal cells (haematological malignancy)
- Polychromasia (RBC different ages, stain differently)
- Heinz bodies/bite cells/blister cells (G6PD)
- Prickle cells (pyruvate kinase deficiency)
- Sperocytes (hereditary spherocytosis/autoimmune haemolytic anaemia)
- Elliptocytes (hereditary elliptocytosis)
- Thick/thin films (malaria)
Direct Coombes test (direct antiglobulin test)
* Detects Abs/complement against RBC’s that are actually on the RBC’s (by adding anti-human Abs - Coombes reagent +ve test indicates an immune mediated cause (e.g. autoimmune haemolytic anaemia)
Indirect Coombes test (pre-natal testing/before blood transfusion, detect Abs against RBC’s that are free in the serum (by adding donor sample to recipients and using Coombes reagent)
G6PD enzyme assay
* After acute attack to exclude G6PD
Hb electrophoresis
* To detect haemoglobinopathies
What are the urine tests for haemolytic anaemia investigation?
- MSU - dipstick (Hb-uria - if intravascular)
* Assay - urobilinogen
What are the principles of management of haemolytic anaemia?
- Auto-immune haemolytic anaemia - steroids, immunosuppression, splenectomy, avoid the cold
- HUS - supportive treatment, volume plasmapheresis and anti-coagulation
- TTP - Plasmapheresis and infusion of FFP (20% mortality)
- G6PD - prevented by avoiding the precipitants, transfusion during the attack
- Pyruvate kinase deficiency - folate, transfusion, splenectomy
- Hereditary sperocytosis - normally requires splenectomy after the age of 5, life long prophylactic penicillin
- Thalassaemia - lifelong blood transfusions (causes iron overload - risk pituitary dysfunction/DM/cardiac toxicity - so give chelator desferrioxamine), splenectomy, marrow transplant may offer a cure
What is lymphoma?
- Blood disorder caused by malignant proliferations of lymphocytes and precursor cells (Hodgkin’s and NH are defined according to histology - Hodgkin’s has Reed Sternberg Cells)
What are the causes / risk factors for developing Hodgkin’s lymphoma?
- Cause - unknown
- Risk factors - affected sibling x 7 risk increase, EBV (33% may alter host immunity), SLE, post transplant, Weternisation, obesity
How common is Hodgkin’s lymphoma?
- 2-3/100,000 in Western Europe (rare)
- 1500/year in UK
- 2 peaks (18-35 yrs, >60 yrs)
- M:F = 2:1