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Case 17 > Immunodeficiency and infectious diseases > Flashcards

Immunodeficiency and infectious diseases Flashcards

1
Q

what are primary and secondary immunodeficiency disorders?

A

primary immunodeficiency disorders- result from a an intrinsic genetic defect of the immune system, usually congenital leasing to a missing enzyme/ cell type or non-functioning component. usually manifest at earl age and are often very serious
secondary immunodeficiency disorders- they are acquired as a result of another disease, environmental factors, infections or drugs. these are much more common and can manifest at any age.

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2
Q

what are the clinical features of immunodeficiency?

A

increased frequency, severity and duration of infection
unexpected complications or manifestations of infection
infections with organisms normally considered of low pathogenicity
non-infectious manifestations in GI, endocrine and haematological organ systems.

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3
Q

what are common primary antibody immunodeficiencies?

A

PIDs:

  1. selective IgA deficiencies- undetectable levels of IgA in blood/secretions with no other immune deficiencies. most common PID. 4 presentations: asymptomatic (majority), recurrent mucosal infections, allergies or autoimmunity.
  2. transient physiological agammaglobulinaemia of the neonate- delayed IgG production. exaggerated in prematurity
  3. X-linked agammaglobulinaemia- X-linked recessive disorder leading to defective B cell maturation
  4. common variable hypoglobulinaemia- abnormal B cell function leading to a deficit in IgG and at leat one other Ig
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4
Q

what are common secondary antibody immunodeficiencies?

A

chronic leukocyte leukaemia- affects ability of B cells to differentiate into plasma cells
multiple myeloma- cancer of plasma cells leading to abnormal antibodies

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5
Q

what is the therapy for antibody immunodeficiencies?

A

immunoglobulin replacement

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6
Q

what are the common manifestations of antibody immunodeficiencies?

A

bacterial infections (pneumococcus)causing otitis, pneumonia, sinusitis, GI disturbances

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7
Q

what are the common manifestations of lymphocyte immunodeficiencies?

A

recurrent viral, fungal, protozoal and intracellular bacterial infections causing deep seated infections, thrush, p.jirovecii pneumonia, reactivation of latent viral infections

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8
Q

what are some examples of primary leukocyte immunodeficiencies?

A

diGeorge syndrome- deletion of segment of chromosome 22 leading to an underdeveloped thymus affecting T cell number and function
wiskott-aldrich syndrome- affect T cell function due to WAS gene mutations- affect the immune synapse between antigen presenting cell and T cell
SCID- group of diseases which affect lymphocyte development: common gamma chain deficiency, adenosine deaminase deficiency, JAK3 kinase deficiency. rare but potentially fatal

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9
Q

what are some examples of secondary leukocyte immunodeficiencies?

A

malnurtition- can lead to atrophy of the thymus. protein deficiency can lead to decreased T cell number
Hodgkins lymphoma- cancer of lymphocytes
infections: measles, malaria, leprosy, HIV- impaired T and sometimes B cell function
drugs- decrease lymphocyte proliferation and circulating number

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10
Q

what are some common manifestations of phagocyte immunodeficiencies?

A

predominantly bacterial infections which occur at the interface between the host and the environment- accesses, pneumonia, seep seated infections, GI disturbances

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11
Q

what are some examples of phagocyte immunodeficiencies?

A

neutropenia- reduced production or accelerated removal of granulocytes. can be PID or SID
PIDs:
leukocyte adhesion deficiency- failure to mobilise WBCs to tissues
chronic granulomatous disease- failure to kill infectious organisms
SIDs:
malnutrition- decrease in NK cells and abnormal phagocytosis
drugs- decreased phagocytosis

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12
Q

what are some common manifestations of complement immunodeficiencies-

A

recurrent and/or serious bacterial infections
autoimmune disease
angioedema

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13
Q

what are examples of complement immunodeficiency?

A 
PID
C1 inhibitor deficiency (hereditary angioedma)- causes over activation of complement. treated with C1 inhibitor concentrate 
SIDs 
osteomyelitis 
endocraditis 
eculizumab- C5 inhibitor
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14
Q

what are cutaneous fungal infections?

A

limited to the epidermis
include:
athletes foot (tinea pedis)- scaly, itchy skin on feet- between toes (interdigital) or more widespread (moccasin)
fungal infection of the skin (tinea corporis- ringworm)- single/multiple red flat or slightly raised circular ring shaped patches. itchy, scaly skin
fungal infection of the groin (tinea cruris)- scaly itchy skin on inguinal folds and medial thighs
fungal nail infection- abnormal, thickened discoloured brittle nail
tinea versicolor- multiple round discoloured macule commonly on back, chest and upper arms.
tinea capitis- scaly,itchy scalp, hair loss, pustules, crusting, associated fungal infection in other sites

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15
Q

what are subcutaneous fungal infections?

A

affect the dermis, subcutaneous tissues and bone
sporoctrichosis- causes raised bump which grows and becomes an ulcerated open sore
mycetoma- initially a painless lesion or abscess typically on feet which progresses to large sores that leak pus, blood and serum
chromomycosis- chronic infection begins as a painless lump that slowly progresses to form a crusty/scaly abscess

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16
Q

what are the causative agents of systemic fungal infections?

A

coccidiomycosis- coccidiodes immitis. symptoms- flu-like, fatigue, cough, fever, SOB, headache, night sweats, aches and pains.
histoplasmosis- histoplasma capsulatum. symptoms similar to coccidiomycosis
blastomycosis- blastomyces dermatidis. symptoms similar to above
paracoccidiomycosis- paracoccidiodes. symptoms- usually asymptomatic, symptoms of lungs and skin, can have lesions in mouth/throat, weight loss, cough, fever, fatigue, swollen lymph nodes

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17
Q

what are the opportunistic fungal infections?

A

candidiasis (thrush)- candida albicans, affects oral mucosa, gums, throat, vagina. can cause systemic infection in immunocompromised
cryptococcosis- cryptococcus neoformans. commonly mild lung infection. cryptococcal meningitis in AIDS patients
aspergillosis- aspergillus fumigatus. generally affects lungs- can be invasive systemic infection in brain, GI tract
murcomycosis- mucromycetes spp. rhinocerebral murcomycosis- sinus infection that spreads to brain, pulmonary murcomycosis
pneumocystis pneumonia- pneumocystis jivoreci cuases pneumonia

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18
Q

what is the MOA and clinical use of terbinafine?

A

used in cutaneous fungal infections- oral or topical.

inhibits fungal production of ergosterol- essential component of fungal cell membranes

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19
Q

what are the MOA and clinical use of azole anti fungals?

A

inhibit cytochrome P450 enzymes involved in the biosynthesis of cell membrane sterols
used mostly in cutaneous or opportunistic infection

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20
Q

what is the MOA and clinical use of nystatin?

A

binds to ergosterol and forms pores- osmotic competence lost
used in candidiasis

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21
Q

what is the MOA and clinical use of amorolfine?

A

inhibits ergosterol production

used in fungal nail infections

22
Q

what is the main causative agent of TB?

A

mycobacterium tuberculosis- aerobic rod shaped, gram stain doesn’t work, acid fast-stains pinky/purple

23
Q

what is the course of TB infection?

A

30% exposed to TB will be infected
90% will get immune activation and granuloma formation and the infection becomes latent- <10% will reactivate and cause active disease
10% will have a failure of immune activation leading to primary active disease.

24
Q

what are the symptoms of active pulmonary TB?

A

general symptoms- fever, weight loss, night sweats, malaise

pulmonary symptoms- persistent productive cough, breathlessness, haemoptysis

25
Q

what are the features of active extrapulmonary TB?

A

presents with symptoms specific to site involved- lymph nodes, CNS, bones and joints, pericardium, Genito-urinary

26
Q

what are granulomas?

A

cellular aggregates which contain the TB infection, important pathological hallmarks fro TB

27
Q

what is the treatment for TB?

A

active- 6 months of isoniazid (with pyridoxine) with rifampicin, supplemented with two months of pyrazinamide and ethambutol
latent- 3 months of isoniazid (with pyridoxine) and rifampicin OR 6 months of isoniazid (with pyridoxine)

28
Q

how can TB be prevented?

A

vaccination (BCG), quality diagnosis, completing treatment regimen, contact tracing, latent TB screening

29
Q

what is the pathogenesis of CMV?

A

primary infection- lytic replication in wide range of organs
latency- in blood cells- mainly CD34+ lymphocytes
reactivation- due to loss of T cell based immunity

30
Q

what is the seroprevalence and transmission of CMV?

A

seroprevalence- about 40% in young adults and increases with age
transmission- contact with infected secretions- saliva, sexual, blood (immunocompromised need blood transfusions free of CMV)

31
Q

what are the clinical features of CMV infection?

A

usually asymptomatic in immunocompetent (may possibly lead to long term conditions e.g atherosclerosis, immune senescence due to chronic inflammation)
congeintal CMV- IUGR, hepatomegaly, encephalitis, neurological problems, developmental delay
immunocompromised:
CMV syndrome- fever, neutropenia
organ invasive disease- retinitis, encephalitis, pneumocystis, myocarditis, hepatitis

32
Q

what are the CMV risks in transplant?

A

solid organ transplant- greatest risk if donor positive recipient negative
stem cell transplant- greatest risk if donor negative recipient positive as donor bone marrow has no CMV specific T cells to control the infection

33
Q

how is CMV diagnosed, treated and prevented?

A

diagnosis- detection of viral DNA by PCR in blood, histology- owls eye inclusions
treatment- ganciclovir (inhibits viral DNA polymerase) used in congenital and immunocompromised
prevention- prophylaxis- oral valganciclovir (pro-drug) post transplant, pre-emptive monitoring

34
Q

what is the pathogenesis of EBV?

A

primary infection- replicates in wide variety of cells including epithelial and B cells
latency- latent in B cells
reactivation

35
Q

what is the seroprevalence and transmission of EBV?

A

95% seropositive by age 40

transmission- direct contact with infected secretions- saliva- kissing disease

36
Q

what are the clinical features of EBV infection?

A

young children- usually asymptomatic, can have sore throat
adolescence- infectious mononucleosis (mono, granular fever)- triad of low grade fever, lymphadenopathy, sore throat. can have abnormal liver function and splenomegaly.

37
Q

how is EBV diagnosed and treatment?

A

monospot test- detects antibodies in acute primary infection.
serology- Viral capsid protein IgM AND IgG
treatment- usually self limiting- no effective antivirals or vaccine

38
Q

what cancers is EBV associated with?

A

burkitts lymphoma- highly malignant B cell tumour
nasopharyngeal cancer- tumour of head and neck
post-transplant lymphoproliferative disorder (PTLD)- occurs in situations of reduced T cell immunity, results in uncontrolled EBV replication which causes uncontrolled B cell proliferation

39
Q

what are the clinical characteristics of HHV6 and 7?

A

transmission- contact with infected secretion
symptoms- roseola infantum- rash in infants, fever can be asymptomatic
complications- febrile convulsions, encephalitis

40
Q

what is the seropositivity and clinical features of HHV8

A

30% general seropositivity

associated with kapok’s sarcoma- cancer of skin and mouth, seen mainly in HIV

41
Q

what is the mechanism of action and resistance of NRTIs?

A

nucleotide reverse transcriptase inhibitors e.g retrovir
NRTIs mimic nucleotides and are picked up by reverse transcriptase and placed in the growing DNA chain which stops further replication
mechanism of resistance- NRTI removed by mutant reverse transcriptase or lack of binding of reverse transcriptase to NRTI

42
Q

what is the mechanism of action of NNRTIs?

A

non-nucleotide reverse transcriptase inhibitors

bind directly to reverse transcriptase and prevents it from functioning

43
Q

what is the mechanism of action and resistance of protease inhibitors?

A

protease is an enzyme that is used to break up viral poly proteins which are used to make new viruses. protease inhibitors block the breakdown of these proteins so new viruses cannot be made
resistance- conformational change in the protease

44
Q

what is the mechanism of action of fusion inhibitors, CCR5 inhibitors and integrates inhibitors?

A

fusion inhibitor T20- prevents fusion of HIV to CD4 cell by preventing hair pinning of the gp41 molecule
CCR5 inhibitor- CCR5 tropic viruses require CCR5 for entry. CCR5 inhibitors therefore prevent viral entry
integrase inhibitors- prevent integration of viral DNA into the host genome

45
Q

what is the principles of ART?

A

antiretroviral therapy- involves taking a combination of drugs to prevent resistance:
dual NRTI and single integrase inhibitor
dual NRTI and single protease inhibitor
dual NRTI and single NNRTI

46
Q

what is post exposure prophylaxis?

A

PEP prevents HIV in these who have had recent exposure to HIV (needle stick, unprotected sex)
raltegavir (integrase inhibitor) and Truvada (2x NRTI- tenofovir, emtricitabine)

47
Q

what is pre-exposure prophylaxis?

A

Truvada reduces risk of transmission in high risk populations

48
Q

what are the social and psychological factors of risk and risk taking behaviour?

A

psychological- optimism bias (it won’t happen to me), perception of benefit or need may off set the perceptions of risk
social- impact of media- misinformation, demographic factors- age, culture, ethnicity, access to health care

49
Q

what is the definition of stigma?

A

social judgement based on an enduring feature of identity conferred by a health problem or condition (HIV, epilepsy, MH)

50
Q

what is the stigma surrounding HIV/AIDS?

A

the irrational or negative attitudes, behaviours and judgements towards people living with or at risk of HIV. it can negatively impact the health and wellbeing of these people by discouraging them from learning their HIV status, accessing treatment, seeking HIV prevention or talking openly with their sexual partners
populations disproportionately affected by HIV are also often affected by stigma due to things such as their race, gender, sexual orientation, gender identity, drug use or sex work

51
Q

what can be done about HIV stigma?

A

talk about HIV- normalise the subject, correct misconceptions, educate about appropriate language
make testing more routine and easy to access
education on the effectiveness of treatment options and how to live life with HIV
education on safe sex and the risks of HIV

Case 17 (2 decks)

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