Q Fever

An acute disease caused by Coxiella burnetii (Rickettsia burnetii) and characterized by sudden onset of fever, headache, malaise, and interstitial pneumonitis.

Symptoms and Signs

The incubation period varies from 9 to 28 days and averages 18 to 21 days. Onset is abrupt, with fever, severe headache, chills, severe malaise, myalgia, and, often, chest pains. Fever may rise to 40° C (104° F) and persist for 1 to > 3 wk. Unlike other rickettsial diseases, Q fever is not associated with a cutaneous exanthem. A nonproductive cough and x-ray evidence of pneumonitis often develop during the 2nd wk of illness.

In severe cases, lobar consolidation usually occurs, and the gross appearance of the lungs may resemble that of bacterial pneumonia

About 1/3 of patients with protracted Q fever develop hepatitis, characterized by fever, malaise, hepatomegaly with right upper abdominal pain, and possibly jaundice. Liver biopsy specimens show diffuse granulomatous changes, and C. burnetii may be identified by immunofluorescence.

HERPES SIMPLEX

An infection with herpes simplex virus characterized by one or many clusters of small vesicles filled with clear fluid on slightly raised inflammatory bases.

The two types of herpes simplex virus (HSV) are HSV-1 and HSV-2. HSV-1 commonly causes herpes labialis, herpetic stomatitis, and keratitis; HSV-2 usually causes genital herpes, is transmitted primarily by direct (usually sexual) contact with lesions, and results in skin lesions

Primary infection of HSV-1 typically causes a gingivostomatitis, which is most common in infants and young children. Symptoms include irritability, anorexia, fever, gingival inflammation, and painful ulcers of the mouth.

Primary infection of HSV-2 typically occurs on the vulva and vagina or penis in young adults

Herpetic whitlow, a swollen, painful, and erythematous lesion of the distal phalanx, results from inoculation of HSV through a cutaneous break or abrasion and is most common in health care workers.

Pneumoconioses—are environmentally related lung diseases that result from chronic inhalation of various substances.

1. Silicosis (stone mason’s disease) 
a. Inhalant: silica dust.
b. Associated with extensive fibrosis of the lungs.
c. Patients have a higher susceptibility to tuberculosis infections.

2. Asbestosis
a. Inhalant: asbestos fibers.
b. Associated with the presence of pleural plaques.
c. Consequences include:
(1) Mesothelioma (malignant mesothelial tumor).
(2) Bronchogenic carcinoma.

3. Anthracosis
a. Inhalant: carbon dust.
b. Usually not as harmful as silicosis or asbestosis.
c. Associated with the presence of macrophages containing carbon.

Thalassaemia. Genetic based defect in synthesis of one of the normal chains.

Beta thalassaemia --->  reduced Hb A and increased HbF (α2, Y2) HBA2(α2)

Alpha thalassaemia  --->   reduced  Hb-A, Hb-A2 and Hb-F-with formation of Hb-H(β4) and Hb Barts (Y4).
Thalassaemia may manifest as trait or disease or with intermediate manifestation.

Features:
•    Microcytic hypochromic RBC is in iron deficjency.
•    Marked anisopoikilocytsis  with prominent target cells.
•    Reticulocytosis and nucleated RBC seen.
•    Mongoloid facies and X-ray findings characteristic of marrow hyperplasia
•    Decreased osmotic. fragility.
•    Increased marrow iron (important difference from iron deficiency anaemia).
•    Haemosiderosis, especially with repeated transfusions.

Diagnosis is by Hb electrophoresis and by Alkali denaturation test (for HbF).

Cytopathologic techniques

Cytopathology is the study of cells from various body sites to determine the cause or nature of disease.

Applications of cytopathology:

1. Screening for the early detection of asymptomatic cancer

2. Diagnosis of symptomatic cancer

3. Surveillance of patients treated for cancer

Cytopathologic methods

There are different cytopathologic methods including:

1. Fine-needle aspiration cytology (FNAC) -In FNAC, cells are obtained by aspirating the diseased organ using a very thin needle under negative pressure.

Superficial organs (e.g. thyroid, breast, lymph nodes, skin and soft tissues) can be easily aspirated.

Deep organs, such as the lung, mediastinum, liver, pancreas, kidney, adrenal gland, and retroperitoneum are aspirated with guidance by fluoroscopy, ultrasound or CT scan.

1. Exfoliative cytology

Refers to the examination of cells that are shed spontaneously into body fluids or secretions. Examples include sputum, cerebrospinal fluid, urine, effusions in body cavities (pleura, pericardium, peritoneum), nipple discharge and vaginal discharge.

1. Abrasive cytology

Refers to methods by which cells are dislodged by various tools from body surfaces (skin, mucous membranes, and serous membranes). E.g. preparation of cervical smears with a spatula or a small brush to detect cancer of the uterine cervix at early stages.

Graves disease 

Graves disease is an organ-specific autoimmune disorder that results in thyrotoxicosis due to overstimulation of the thyroid gland by autoantibodies. 
- It is the most common form of thyrotoxicosis, females being affected more than males by 8: 1. 
- It is usually associated with a diffuse enlargement of the thyroid.

Pathogenesis
 
IgG-type immunoglobulins bind to TSH membrane receptors and cause prolonged stimulation of the thyroid, lasting for as long as 12 hours 
(cf. 1 hour for TSH). The autoantibody binds at a site different to the hormone-binding locus and is termed the TSH-receptor autoantibody (TRAb); 95% of Graves’ disease patients are positive for TRAbs

Gross features 
- The thyroid gland is diffusely and moderately enlarged
- It is usually smooth, soft, and congested  

Histologically
- the gland shows diffuse hypertrophy and hyperplasia of acinar epithelium, reduction of stored colloid and local accumulations of lymphocytes with lymphoid follicle formation.

Clinical features

- Exophthalmos (protrusion of the eyeballs in their sockets)—due to the infiltration of orbital tissues by fat, mucopolysaccharides and lymphocytes. May cause compression of the optic nerve, hence blindness. However, only about 5% of Graves’ patients show signs of exophthalmos.
- Thyroid acropachy—enlargement of fingernails. 
- Pretibial myxoedema—accumulation of mucoproteins in the deep dermis of the skin.

Treatment is as for thyrotoxicosis.