The following describes your patient’s clinical presentation: A 19-year-old Cauc

Question

The following describes your patient’s clinical presentation:

A 19-year-old Caucasian female in her first year at University presented in A&E with confusion, irritability, marked neck stiffness, petechial rash and a body temperature of 38.5oC. In the preceding 24h, the patient had experienced a severe occipital headache with vomiting. A CSF sample was then obtained by lumbar puncture and analysed and the results obtained are shown in Table A:

Table A: Results of the analysis of the patient’s CSF sample

Parameter measured

Result

Reference range

Appearance

Cloudy & turbid

Clear & colourless

Protein

5.2 g/L

0.2 – 0.4 g/L

Glucose mmol/L

0.18 mmol/L

3.3 – 4.4 mmol/L

White cells

4800 x 106/L

97% neutrophils

0 – 5 x 106/L

All lymphocytes

No neutrophils

Red Cells

6.2 x 106/L

0 – 10 x 106/L

Microbiology

Positive for Neisseria meningitides

N/A

The patient was treated with intravenous cefotaxime and made a full recovery. The patient then reported a previous N. meningitides infection at aged 13 years with N. meningitides serogroup Y so, following recovery, further investigations were undertaken to evaluate her immune function. The results obtained are presented in Table B:

Table B: Results of immune screen

Parameter

Result

Reference Range

Serum IgG

12.1 g/L

6.0 – 16.0 g/L

Serum IgA

2.8 g/L

0.8 – 4.0 g/L

Serum IgM

1.2 g/L

0.5 – 2.0 g/L

AH50

0 units

80 – 200 units/mL

CH50

0.6

100- 500 units/mL

Based on the above and in light of the results you have obtained, what possible underlying cause(s) have led to the patient’s reduced resistance to N. meningitides? Explain your rationale.

Parameter measured

Result

Reference range

Appearance

Cloudy & turbid

Clear & colourless

Protein

5.2 g/L

0.2 – 0.4 g/L

Glucose mmol/L

0.18 mmol/L

3.3 – 4.4 mmol/L

White cells

4800 x 106/L

97% neutrophils

0 – 5 x 106/L

All lymphocytes

No neutrophils

Red Cells

6.2 x 106/L

0 – 10 x 106/L

Microbiology

Positive for Neisseria meningitides

N/A

Explanation / Answer

The AH50 and CH50 assay levels are lower.

CH50 assay stands for the total hemolytic complement assay. It is the best screening assay for most complement abnormalities. CH50 assay assesses the classical complement pathway including both the early components that activate the pathway in response to immune complexes, as well as the late components involved in the membrane attack complex.

The complement alternate pathway (AH50) assay is a screening test for complement abnormalities in the alternative pathway. Patients with deficiencies in the alternate pathway factors (D, B, P, H, and I) or late complement components (C3, C5-C9) are susceptible to recurrent neisserial meningitis.

Therefore, in the given patient there is an abnormality of late complement complexes (C3, C5-C9).

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