Acute leukaemia
Lympheblastic is commoner in children and myeloblastic in adults .

Features:
- Anaemia.
- Fever and infections especially oral and respiratory.
- Haemorrhagic tendencies.
- Bone pains and tenderness (sternal).
- Lymphnode enlargement especially in lymphocytic.
- Gum hypertrophy especially in monocytic.

Blood picture:

- Anaemia and thrombocytopenia.
- Leucocyte count usually 20,-50,000/cu.mm. It may be less in subleukaemic leukaemia (even leucopenic levels may be seen).
- Blast cells form 30-90% of cells. Smudge cells and basket cells are seen .The type of balst cell may be recognised  by the associated more mature forms or by special cytochemical stains
- Blasts may be few in peripheral blood in the aleukamic stage

 Bone Marrow

- May be a dry tap , necessitating a trephine biopsy 
- Hypercellular with 70-90% blasts
- Reduction in megakaryocytes and erythroid cells
 

Alcoholic (nutritional, Laennec’s) cirrhosis

Pathology
 
Liver is at first enlarged (fatty change), then return to normal size and lastly, it becomes slightly reduced in size (1.2 kg or more).
- Cirrhosis is micronodular then macronodular then mixed.   

M/E  
Hepatocytes:-  show fatty change that decreases progressively. Few hepatocytes show increased intracytoplasmic haemochromatosis. 
b. Fibrous septa:-  Regular margins between it and regenerating nodules.
 -Moderate lymphocytic infiltrate.      
 – Slight bile ductular proliferation.
 
Prognosis:-   It Progresses slowly over few years. 

Psoriasis is a chronic disorder characterized by scaly, erythematous plaques, which histologically are secondary to epidermal proliferation.
 - genetic factors (HLA relationships), environmental (physical injury, infection, drugs, photosensitivity), abnormal cellular proliferation (deregulation of epidermal proliferation) and microcirculatory changes in the papillary dermis (diapedesis of neutrophils into the epidermis) are all interrelated.
 - the plaques of psoriasis are characteristically well-demarcated pink or salmon colored lesions covered by a loosely-adherent silver-white scale which, when picked off, reveals pinpoint bleeding sites (Auspitz sign).
 - the nail changes in psoriasis include pitting, dimpling, thickening and crumbling with a yellowish-brown discoloration of the nail plate.
 - the characteristic histologic features of psoriasis include:
 - hyperkeratosis
 - absence of the granulosa cells (present in lichen planus).
 - parakeratosis
 - regular, club-shaped elongation of the rete pegs (irregular and saw toothed in lichen planus) with vessel proliferation in the papillary dermis (reason for the bleeding associated with Auspitz sign).
 - characteristic subcorneal collection of neutrophils called a Munro's microabscess (diapedesis from vessels in papillary dermi).
 - 7% develop HLA B27 positive psoriatic arthritis

Rickets and Osteomalacia 

Rickets in growing children and osteomalacia in adults are skeletal diseases with worldwide distribution. They may result from
1. Diets deficient in calcium and vitamin D
2. Limited exposure to sunlight (in heavily veiled women, and inhabitants of northern climates with scant sunlight)
3. Renal disorders causing decreased synthesis of 1,25 (OH)2-D or phosphate depletion 
4. Malabsorption disorders.

Although rickets and osteomalacia rarely occur outside high-risk groups, milder forms of vitamin D deficiency (also called vitamin D insufficiency) leading to bone loss and hip fractures are quite common in the elderly.

Whatever the basis, a deficiency of vitamin D tends to cause hypocalcemia. When hypocalcemia occurs, PTH production is increased, that ultimately leads to restoration of the serum level of calcium to near normal levels (through mobilization of Ca from bone & decrease in its tubular reabsorption) with persistent hypophosphatemia (through increase renal exretion of phosphate); so mineralization of bone is impaired or there is high bone turnover.

The basic derangement in both rickets and osteomalacia is an excess of unmineralized matrix. This complicated in rickets by derangement of endochondral bone growth.

The following sequence ensues in rickets:
1. Overgrowth of epiphyseal cartilage with distorted, irregular masses of cartilage
2. Deposition of osteoid matrix on inadequately mineralized cartilage
3. Disruption of the orderly replacement of cartilage by osteoid matrix, with enlargement and lateral expansion of the osteochondral junction
4. Microfractures and stresses of the inadequately mineralized, weak, poorly formed bone
5. Deformation of the skeleton due to the loss of structural rigidity of the developing bones 

Gross features
• The gross skeletal changes depend on the severity of the disease; its duration, & the stresses to which individual bones are subjected.
• During the nonambulatory stage of infancy, the head and chest sustain the greatest stresses. The softened occipital bones may become flattened. An excess of osteoid produces frontal bossing. Deformation of the chest results from overgrowth of cartilage or osteoid tissue at the costochondral junction, producing the "rachitic rosary." The weakened metaphyseal areas of the ribs are subject to the pull of the respiratory muscles and thus bend inward, creating anterior protrusion of the sternum (pigeon breast deformity). The pelvis may become deformed.
• When an ambulating child develops rickets, deformities are likely to affect the spine, pelvis, and long bones (e.g., tibia), causing, most notably, lumbar lordosis and bowing of the legs .
• In adults the lack of vitamin D deranges the normal bone remodeling that occurs throughout life. The newly formed osteoid matrix laid down by osteoblasts is inadequately mineralized, thus producing the excess of persistent osteoid that is characteristic of osteomalacia. Although the contours of the bone are not affected, the bone is weak and vulnerable to gross fractures or microfractures, which are most likely to affect vertebral bodies and femoral necks.

Microscopic features

• The unmineralized osteoid can be visualized as a thickened layer of matrix (which stains pink in hematoxylin and eosin preparations) arranged about the more basophilic, normally mineralized trabeculae.

Infectious Mononucleosis

It is an Epstein Barr virus infection in children and young adults.

Features

-Constitutional symptoms.
-Sore throat.
-Lymphnode enlargement.
-Skin rashes
-Jaundice.
-Rarely pneumonia, meningitis and encephalitis.

Blood Picture

- Total count of I0,000. 20,000 /cu.mm.
- Lymphocytosis (50-90%) with atypical forms. They are larger with more cytoplasm which may be vacuolated or basophilic. Nucleus may be indented. with nucleoli (Downy type I to III).
- Platelets may be reduced.
- Paul Bunell test (for heterophil antibody against sheep RBC) is positive
 

Multiple sclerosis
a. A demyelinating disease that primarily affects myelin (i.e. white matter). This affects the conduction of electrical impulses along the axons of nerves. Areas of demyelination are known as plaques.
b. The most common demyelinating disease.
c. Onset of disease usually occurs between ages 20 and 50; slightly more common in women.
d. Disease can affect any neuron in the central nervous system, including the brainstem and spinal cord. The optic nerve (vision) is commonly affected.