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Case 14: Stiff and Painful Hands
39
RA is also associated with an increased risk of cardiovascular disease, resulting from endo-
thelial activation by inflammatory cytokines. This generalised inflammatory response may
also account for the other systemic manifestations of RA, involving the lungs (fibrosis), bones
(osteoporosis) and brain (reduced cognition), as well as a higher risk of lymphoma.
KEY POINTS
•
Morning stiffness is a common rheumatologic symptom, and the key to distin-
guishing whether it is inflammatory or degenerative in origin is seeing whether it
gets better or worse through the day.
•
RA typically affects the small joints of the hands bilaterally and is associated with
positivity for anti-CCP antibodies.
•
It is believed to arise from the immune system reacting against as-yet unidenti-
fied antigens, provoking the formation of an inflammatory pannus over articular
surfaces.
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CASE 15: ABDOMINAL PAIN, NAUSEA AND
VOMITING
A 15-year-old boy is brought into the emergency department after complaining of abdominal
pain throughout the day. He has been feeling generally unwell for the past couple of days, but
is much worse today with a decline in his level of alertness. He is drowsy but still communi-
cates in sentences and complains of a productive cough. He has had three episodes of non-
bilious, non-bloody vomiting over the past few hours and gives a vague history of drinking
more water in the past few weeks. His past medical history is significant for asthma.
Examination
Physical examination reveals an ill-looking boy with pulse of 100, blood pressure 110/70
mmHg, respiratory rate 24 per minute and shallow, O
2
saturation of 95% on room air,
temperature 35.8°C and Glasgow Coma Scale (GCS) 14 (E4, V4, M6). Auscultation of the
chest is positive for crackles at the right mid and lower zones. Abdominal palpation reveals
a diusely tender abdomen, but no guarding or rebound tenderness. No focal neurology is
demonstrable.
INVESTIGATIONS
Haemoglobin 13.6
White cells 13
Neutrophils 8
Platelets 340
Sodium 138
Potassium 5.2
Chloride 105
Urea 10.9
Creatinine 90
Bilirubin 10
Alkaline phosphatase 56
C-reactive protein 125
Glucose 22.5
Urine dipstick +++ glucose and ketones
ABG (on room air):
pH 7.30
pCO
2
12.1
pCO
2
3.5
HCO
3
17
DOI: 10.1201/9781003242697-16
41
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Case 15: Abdominal Pain, Nausea and Vomiting
43
QUESTIONS
1.
Interpret the arterial blood gas results. What type of disorder is suggested?
2. What are the potential causes of this metabolic disturbance? Which is the likeli-
est cause (given the history and examination)?
3. Discuss the pathophysiology underlying the likely condition. What is the likely
precipitant?
4. What are the principles of managing this patient in the short term?
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100 Cases in Clinical Pathology and Laboratory Medicine
44
ANSWERS
The arterial blood gas is consistent with a partly compensated metabolic acidosis. The low
pH and the low bicarbonate levels confirm that the cause of the acidosis is metabolic; since
pCO
2
is slightly low, there is some degree of respiratory compensation in an eort to blow o
H
+
as CO
2
. This correlates with the clinical finding of a high respiratory rate and shallow
breathing (Kussmaul’s breathing).
When investigating a metabolic acidosis, it is useful to determine the anion gap ([Na
+
] +
[K
+
]– [Cl
−
] – [HCO
3
−
]), as the causes of a normal anion-gap metabolic acidosis are dis-
tinct from those of a raised anion-gap acidosis. Here, the anion gap is 21, which is elevated,
indicating that an unmeasured anion is present in increased quantities (such as lactate,
β-hydroxybutyrate). The causes of a metabolic acidosis with a high anion gap include:
•
Lactic acidosis (e.g., tissue hypoxia, drugs such as metformin and ethanol)
•
Ketoacidosis (e.g., diabetic ketoacidosis)
•
Exogenous acids (e.g., salicylate overdose)
•
Accumulation of organic acids (e.g., inherited organic acidoses)
•
Renal failure (‘uraemic acidosis’)
Here, the likeliest cause is diabetic ketoacidosis (DK A), given the symptoms of abdominal
pain and vomiting on a background of feeling generally unwell with polyuria. The finding
of Kussmaul’s breathing is also characteristic. Additionally, blood tests confirm hyperglycae-
mia, with the presence of both glucose and ketones in urine.
DKA is a medical emergency, accounting for up to 10% of hospital admissions for children
with diabetes. It can often be the first manifestation of a previously undiagnosed case of type
1 diabetes and comprises three key elements: (1) marked hyperglycaemia, (2) ketosis and (3)
acidosis. It results from acute insulin deficiency, which leads to the following:
•
Rapid mobilisation of energy from muscle and fat stores, with conversion of amino
acids to glucose and fatty acids to ketones
•
The low insulin:glucagon ratio and higher levels of catecholamines and cortisol pro-
moting hepatic glycogenolysis and gluconeogenesis
•
Reduced peripheral utilisation of glucose and ketones due to lack of insulin, thereby
leading to hyperglycaemia and ketosis
•
Hyperglycaemia provoking an osmotic diuresis, leading to depletion of intravascu-
lar volume, with reduction in renal blood flow hampering the ability of the kidneys
to excrete glucose, and resultant hyperosmolality, which may lead to central nervous
system (CNS) depression and coma
The precipitating factor here is probably a chest infection. The stress response to infection
invokes a counter-regulatory hormone drive, with a rise in the glucagon:insulin ratio, leading
to the sequence of events described above.
The key aspects of managing DKA are four-fold:
•
Immediate resuscitation
•
Fluid and electrolyte replacement
•
Insulin replacement
•
Treatment of precipitating causes
Emergency management should follow an ABCDE approach and be combined with fluid
resuscitation. At least 2 L of normal saline are required in adult patients in the first 2–3 hours
to reduce the hyperosmolar state, clear ketones and restore extracellular fluid volume. The
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Case 15: Abdominal Pain, Nausea and Vomiting
45
overall fluid deficit in an average adult may be up to 7 L. As soon as fluid resuscitation is under
way, insulin replacement by way of a fixed-rate insulin infusion (0.1 units/kg) is required. The
aim should be to reduce blood ketone concentrations by at least 0.5 mM per hour and capil-
lary blood glucose by 3 mM per hour and to raise venous bicarbonate by 3 mM per hour.
Once blood glucose levels fall below 14 mM, 10% glucose infusion is recommended to avoid
hypoglycaemia, with continuation of the insulin infusion to suppress ketogenesis.
The electrolyte deficiencies in DK A include sodium, potassium, chloride and phosphate.
Potassium losses may be particularly high (though serum levels may be artificially high from
the potassium flux into the extracellular space as a result of acidosis), and generally 40 mmol
of K
+
is given with each bag of normal saline. In addition to these resuscitative measures,
treatment should be directed at the precipitating cause (e.g., antibiotics for chest infection),
and the diabetic specialist team should be involved in management, particularly as they will
be needed to plan long-term treatment.
KEY POINTS
•
Calculation of the anion gap helps distinguish between the causes of a metabolic
acidosis.
•
DKA is a common cause of a raised anion-gap metabolic acidosis and fundamen-
tally results from acute insulin deficiency.
•
Management of DKA is based on replacing the deficient insulin, fluid and electro-
lytes and treating the provoking cause.
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CASE 16: FREQUENT THROAT AND CHEST
INFECTIONS
A 28-year-old woman presents to her GP with a chesty cough that has been ongoing for
4 days and is now productive of green sputum. This is her fourth such episode this year. She
says that she has suered from ‘sinus infections’ since she was a teenager. She has a history
of asthma as well as intermittent abdominal pain and diarrhoea that began after a holiday
to South America.
Examination
Vital signs are T 37.6°C, HR 90, BP 110/65, RR 22, O
2
sat 96% on room air. Physical
examination reveals crackles in the right mid and lower lung zones.
INVESTIGATIONS
Haemoglobin 11.5
White cells 11.5
Platelets 225
IgG Low
IgA Undetectable
IgM Normal
HIV antigen Negative
QUESTIONS
1.
What initial screening tests should be performed if her physician suspects an
immunodeficiency?
2. Assuming there are no secondary causes, what would be the most likely cause of
a primary immunodeficiency in this woman? What do you know about the aetiol-
ogy of this condition?
3. How should this woman be managed for the likely underlying condition? What
other complications need to be monitored for?
DOI: 10.1201/9781003242697-17
47
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100 Cases in Clinical Pathology and Laboratory Medicine
48
ANSWERS
Immunodeficiency should be suspected in patients with severe, persistent, recurrent, or
‘unusual’ infections; in this case, the history of recurrent sinopulmonary infections is suspi-
cious, while the presence of chronic diarrhoea should also raise the suspicion of an infectious
gastroenteritis (e.g., giardiasis).
Immunodeficiency may be either primary (an intrinsic immune system defect) or secondary
to an underlying condition. Important secondary causes of immunodeficiency to consider
are infections (notably HIV), malnutrition, malignancy (particularly haematologic), drugs
(immunosuppressants, immunomodulators), protein-losing states (e.g., nephrotic syndrome,
protein-losing enteropathy) and metabolic disease (e.g., diabetes and severe liver disease).
Initial workup of a suspected immunodeficiency involves taking a pertinent history and per-
forming a complete examination. Investigations should include a full blood count, liver and
renal function tests, urinalysis (for proteinuria), HIV status, measurement of total serum pro-
teins and relevant imaging for sinusitis and chest infections. Measurement of serum immuno-
globulins is crucial to look for antibody deficiencies.
Here, serum immunoglobulin levels show low levels of IgG and IgA with normal IgM levels.
If secondary causes are ruled out, the key causes of primary immunodeficiency to consider
are (1) common variable immunodeficiency (CVID), (2) X-linked agammaglobulinaemia
(XLA), (3) selective Ig subclass deficiency and (4) hyper-IgM syndrome. All cause antibody
deficiency, but XLA presents in the neonatal period, while levels of IgM are greatly increased
in hyper-IgM syndrome. Selective Ig deficiency may be a possibility here, but is less likely
given that two dierent immunoglobulins are deficient. Hence, the most likely diagnosis,
partly by exclusion and partly because of the age of the patient, is CVID.
CVID, the most common symptomatic primary immunodeficiency, typically presents in late
childhood with recurrent sinopulmonary and bacterial infections as well as gastrointestinal
complications. Capsulated bacteria (Haemophilus influenzae and Streptococcus pneumoniae) account
for the bulk of respiratory infections, while Giardia is more frequent given the deficiency in
mucosal antibody defences.
CVID is usually sporadic, and though the molecular basis of the disease is incompletely
understood, the defect lies in the inability of B cells in blood and lymphoid tissue (present in
normal numbers) to dierentiate into plasma cells. It is unclear whether this is an intrinsic
B-cell problem or whether the fault lies with a defective ability of T cells in activating B cells.
The mainstay of CVID management is immunoglobulin replacement and prompt treatment
of infections. Further, attention should be paid to potential complications of CVID, which
include an increased risk of autoimmune disease (e.g., haemolytic anaemia), lung disease
(e.g., bronchiectasis, fibrosis), granulomatous disease (usually aecting the lung) and cancer
(particularly lymphoid malignancy).
KEY POINTS
•
Suspect an immunodeficiency if there is evidence of severe, persistent, recurrent
or unusual infections.
•
Immunodeficiency may be either primary or secondary to an underlying condition
such as HIV.
•
CVID is the most common symptomatic primary immunodeficiency and is due to a
defect in differentiation of B cells into antibody-secreting plasma cells.
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