Page 70 - Problem-Based Feline Medicine

62 PART 2 CAT WITH LOWER RESPIRATORY TRACT OR CARDIAC SIGNS

Clinical signs Endocrine testing involves measurement of total T4
and free-T4 (hyperthyroidism), blood and urine glu-
Dyspnea associated with myopathy or neuropathy is
cose, fructosamine concentration (diabetes mellitus),
related to weakness of the intercostal and diaphragmatic
or ACTH stimulation testing (hyperadrenocorticism)
muscle, causing diminished ventilation.
if clinical signs are consistent.
Signs related to the underlying disease will be evident,
Acetylcholine receptor antibodies assay is used for
for example:
myasthenia gravis.
● Hyperthyroid myopathy is usually seen in older
cats. Signs include ravenous appetite, restlessness, Measurement of muscle enzymes (creatine phosphoki-
weight loss, poor haircoat, generalized muscle nase activity) and muscle biopsy are necessary for diag-
wasting and weakness. nosis of myositis.
● Hypokalemic myopathy occurs in older cats usu-
ally secondary to renal insufficiency, or in Burmese PNEUMONIA
cats less than 1 year of age. Ventroflexion of the
head, a stiff stilted gait, inability or reluctance to
Classical signs
walk or jump are common signs. Sensitivity to
palpation of the larger muscle groups may be ● Cough.
evident. ● Inspiratory/expiratory dyspnea.
● Hypocalcemic myopathy results in episodic gen- ● Fever.
eralized weakness, tetany or tremors. It occurs ● Occasional nasal discharge.
most commonly after thyroidectomy, but occa-
sionally occurs with hypoparathyroidism, chronic Pathogenesis
renal failure, pancreatitis, eclampsia or phosphate-
containing enemas. Pneumonia may be primary or secondary and asso-
● Hyperadrenocorticism results in poorly controlled ciated with bacterial, mycoplasmal, Chlamydophila
diabetes mellitus, unkempt haircoat, pot-bellied felis, fungal or viral agents.
appearance and generalized muscle weakness.
Primary bacterial pathogens include Bordetella
● Myasthenia gravis occurs typically in adult
bronchiseptica and Pasteurella multocida, which are
cats or Siamese < 1 year of age and presents
common flora of the oropharynx, and can colonize the
as generalized muscle weakness and stiff stilted
lower respiratory tree.
gait exacerbated with exercise. Severe dyspnea
may be evident if aspiration pneumonia is Secondary bacterial infection is possible with many
present. opportunist organisms including streptococci, Bordetella
● Polymyositis produces generalized pain on palpa- bronchiseptica, Pseudomonas spp., Nocardia spp. and
tion of muscle groups, and a stiff stilted gait. Actinomyces spp.
● Botulism toxicity results in flaccid paralysis of
Pneumonia may occur following lung damage from
skeletal or respiratory muscles.
various sources, or associated with diseases that reduce
● Polyradiculoneuritis produces an ascending flac-
immunocompetence such as:
cid paralysis of sketetal and respiratory muscles.
● Aspiration as a result of esophageal dysmotility, or
● Tick paralysis from Demacentor spp. and Ixodes
during recovery from general anesthesia, etc.
spp. ticks, produces a rapidly progressive skeletal
● Metabolic disease including uremic pneumonitis,
and respiratory paralysis.
hyperadrenocorticism and diabetes mellitus.
● Trauma (blunt, penetrating or surgical trauma).
● Immunosuppression from drugs, neoplasia, or
Diagnosis retroviral infection.
● Pre-existing infection.
Serum electrolytes (i.e., potassium and calcium) should
be measured to rule out hypokalemia and hypocal- Mycoplasma pneumonia is rare, but may be a sequel
cemia. of severe URT infection.