Defensive Breakdown & Bone Marrow

Question 1

List some opportunistic HIV and AIDS infections

Answer 1

HIV:
Fungal - pneumocystis jiroveci, Candida albicans, aspergillus fumigatus, histoplasma capsulatum, cryptococcus neoformans
AIDS:
Mycobacterium - tuberculosis, avium intracellulare
Parasites - cryptosporidium, isospora, toxoplasma gondii
Viral - CMV, herpes zoster, herpes simplex
Bacteria - haemophilus influenzae, streptococcus pneumoniae

Question 2

Describe the sites of haemopoiesis in the foetus, child and adult

Answer 2

Fetus - yolk sac, liver, spleen, bone marrow
Child - bone marrow of most bones
Adult - bone marrow of vertebrae, ribs, sternum, sacrum, pelvis, proximal ends of femur

Question 3

Describe the structure of bone marrow

Answer 3

Production of red blood cells, white blood cells, platelets
Red marrow - haematopoietic tissue
Yellow marrow - fatty tissue

Question 4

Describe how cytopenia or pancytopenia can develop

Answer 4

Thrombocytopenia - immune destruction (autoantibodies), pathological activation of coagulation, B12/folate deficiency, malignancy, aplastic anaemia, drugs, viruses
Neutropenia - B12/folate deficiency, malignancy, aplastic anaemia, drugs, viruses, congenital
Pancytopenia - drugs, congenital bone marrow failure (Fanconi’s anaemia)

Question 5

Describe the clinical manifestation of pancytopenia or individual cytopenia (neutropenia or thrombocytopenia)

Answer 5

Pancytopenia - fatigue, dizziness, bruising, infections, ulcers, fever
Neutropenia - severe, life threatening bacterial/fungal infections
Thrombocytopenia - easy bruising, petechiae, purpura, mucosal bleeding, severe bleeding after trauma, intracranial haemorrhage

Question 6

Describe the structure and function of the spleen

Answer 6

Red pulp - sinuses lined by endothelial macrophages and cords (RBCs preferentially pass through)
White pulp - similar to lymphoid follicles (WBCs, plasma preferentially pass through)
Functions - sequestration, phagocytosis, blood pooling, extramedullary haemopoiesis, immunological

Question 7

List some causes of hyposplenism and splenomegaly

Answer 7

Hyposplenism - Howell Jolley bodies, sickle cell anaemia, coeliac disease
Splenomegaly - sarcoidosis, infections, cirrhosis, myeloid leukaemia, malaria

Question 8

Be aware of the range of congenital and acquired immunodeficiency syndromes

Answer 8

Congenital:
B cell - X linked hypogammaglobulinaemia
T cell - DiGeorges syndrome
Both - SCID
Neutrophils - chronic granulomatous disease
Ataxia telangiectasia
Acquired:
B cell - hypogammaglobulinaemia
T cell - HIV, chemotherapy, Hodgkins disease, Immunosuppression
Both - radiotherapy, chronic lymphoid leukaemia, malnutrition
Neutrophils - neutropenia, myelodysplasia