Group 3 final case - Cal State LA

Final Case Study: Case #3 Rabin Anouseyan Alex Huynh Kimberly Rampasan California State University, Los Angeles Department of Biological Sciences

Case summary: patient overview 

Martin Causubon, exact age unknown  Over 5 years old and treated by pediatrician

Biological sister with no symptoms  Severely underweight  High susceptibility to recurrent infections  Abnormal leukocytes 

 Cell numbers  Cellular responses

Case summary: recurrent infections • • • • • •

Recurring infections since 3 months of age Multiple occurrences of otitis media (inner ear infection) Persistent cough caused by pneumonia in both lungs Multiple occurrences of thrush, caused by Candida spp. Many rashes in diaper area Infections persisted despite treatment with different antibiotics (amoxicillin, clarithromycin)

Case summary: abnormal leukocytes • • • • •

Slightly low white blood cell count Extremely low absolute lymphocyte count Complete lack of T cells Low numbers of NK cells Presence of B cells – Very low IgG concentration – IgA and IgM concentrations at lower end of normal range

•

Mononuclear cells unreactive to: – – – –

•

Phytohemagglutinin (PHA) Concanavalin A (ConA) Mitogens Pokeweed mitogen (PWM) Specific antigens which he had been previously exposed to

Normal adenosine deaminase and purine nucleoside phosphorylase

Diagnosis for Case 3: X-linked severe combined immunodeficiency •

Genetic disorder – X-linked recessive

•

Mutation in IL2RG gene on X chromosome – Common γ chain of interleukin-2 receptor • IL-2: major cytokine involved in T cell growth and maturation – Failure of T cell maturation due to

underdeveloped thymus – Low or absent B cell activity due to low T cells •

Most common form of SCID – May affect 1 in 50,000

http://ghr.nlm.nih.gov/dynamicImages/chromomap/IL2RG.jpeg

Key elements of X-SCID •

•

Affected male with unaffected sister Recurrent infections since young age – Infections begin after depletion of maternal IgG

• • • • •

Deficiency in T cells and low numbers of natural killer cells Unresponsive B cells: no response to immunizations Low levels of immunoglobulins, particularly IgG Failure to gain weight and grow normally Normal adenosine deaminase and purine nucleoside phosphorylase – Rules out adenosine deaminase deficiency and purine

nucleoside phosphorylase deficiency (other forms of SCID)

Diagnostic tests for X-SCID 

Lymphocyte counts  Flow cytometry using markers for T cells (CD3),

B cells (CD19) and NK cells (CD56)  Positive result: low numbers of T cells and NK cells ○ Normal B cell numbers



Lymphocyte functional tests  Use mitogens and specific antigens to induce B

cell proliferation  Positive result: low proliferative macrophage and B cell response  

Genetic analysis: mutation in IL2RG gene Analysis of immunoglobulin concentrations

X-SCID therapies and treatments 

Bone marrow transplant  From an allogeneic HLA-matched donor  Provides self-renewing supply of healthy immune

cells  High success rate within first three months of life    

Immunoglobulin treatments Gene therapy Aggressive antibiotic treatments at signs of infection Very clean or sterile environment to minimize pathogen exposure

Prognosis for X-SCID Relatively normal life after successful bone marrow transplant and continued gamma-globulin therapy  High level of mortality if severe opportunistic infection takes place before diagnosis and/or treatment of XSCID 

 Occurs with most X-SCID cases: infant

mortality is common

Communicating the diagnosis Sorry Mr. and Mrs. Causubon, I regret to inform you that your son, Martin has been diagnosed with X-linked severe combined immunodeficiency. X-SCID is a severe immunodeficency which disables your son’s ability to fight against infections. The good news is that there some treatments that have been shown to be effective, however, as with all treatments, we cannot guarantee full recovery. The most common treatment for this disease is a bone marrow transplant. If we act quickly and start treatment immediately, the prognosis might be optimistic. Those who undergo successful bone marrow transplants tend to leave normal lives. Without any treatment, prognosis is very dim. I would recommend immediate testing to determine if you or any of your immediate family members are matches for a bone marrow transplant.

Theoretical immunological basis for X-SCID 

T-helper (TH) cells have a main role in activating the adaptive immune response  TH1 cytokine secretion augments response  Activate infected macrophages ○ IFNγ, GM-CSF, TNFα  Induce class switch in B cells ○ CD40 ligand ○ Fas ligand

Primary research article Ravin et al., 2008. Journal of Pediatric Endocrinology & Metabolism •

X-SCID patients are characterized by very short stature (< 5th percentile) – γC (mutated in X-SCID) has been implicated in growth hormone

(GH) signaling • •

Objective: examine levels of GH in normal and X-SCID age-matched males Methods: collected blood from patients – Treat with GH (low levels) for 5 days – Measure IGF-1 levels by immunoradiometric assay at day 0, 5

and 8 •

Major results: significant reduction of IGF-1 in X-SCID patients compared to normal patients at all time points – Possible treatment: high-level doses of GH

IGF-1 plasma levels (ng/ml)

Key figure  Normal males

 X-SCID males

Days after recombinant growth hormone treatment

Take Home Messages •

•

X-SCID involves the absence of T cells, NK cells, and nonfunctional B cells Typical symptoms – Rashes – Diarrhea – Recurrent opportunistic infections •

•

• •

Candida spp.

Diagnostics include genetic analysis, lymphocyte counts, lymphocyte functional tests, and analysis of immunoglobulin concentrations Therapy is based on genetic therapy, bone marrow transplants, and immunoglobulin treatments Prognosis is excellent after a successful bone marrow transplant • Late diagnosis and treatment typically leads to infant mortality from a

severe infection