Ichthyosis vulgaris is a genetic disease characterized by increased cohesiveness of the cells in the stratum corneum, resulting up in a piling up stratum corneum (scales like a fish).

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.

Agranulocytosis. Severe neutropenia with symptoms of infective lesions.

Drugs. are an important cause and the effect may be due to .
-Direct toxic effect.
-Hypersensitivity.

Some of the 'high risk drugs are.
-Amidopyrine.
-Antithyroid drugs.
-Chlorpromazine, mapazine.
-Antimetabolites and other drugs causing pancytopenia.

Bloodpicture:  Neutropenia with toxic granules in neutrophils. Marrow shows decrease in granulocyte precursors with toxic granules in them.

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.

Cardiac arrhythmia

Cardiac arrhythmia is a group of conditions in which muscle contraction of the heart is irregular for any reason.

Tachycardia :A rhythm of the heart at a rate of more than 100 beats/minute , palpitation present
Causes : stress, caffeine, alcohol, hyperthyroidism or drugs

Bradycardia : slow rhythm of the heart at a rate less than 60 beats/min 

Atrial Arrhythmias 

- Atrial fibrillation

Atrial Dysrhythmias 

- Premature atrial contraction
- Atrial flutter
- Supraventricular tachycardia
- Sick sinus syndrome

Ventricular Arrhythmias 

- Ventricular fibrillation

Ventricular Dysrhythmias 

- Premature ventricular contraction
- Pulseless electrical activity
- Ventricular tachycardia
- Asystole

Heart Blocks 

- First degree heart block
- Second degree heart block 
o    Type 1 Second degree heart block a.k.a. Mobitz I or Wenckebach
o    Type 2 Second degree heart block a.k.a. Mobitz II
- Third degree heart block a.k.a. complete heart block

Atrial fibrillation

Atrial fibrillation  is a cardiac arrhythmia (an abnormality of heart rate or rhythm) originating in the atria.
AF is the most common cardiac arrhythmia

Signs and symptoms

Rapid and irregular heart rates
palpitations, exercise intolerance, and occasionally produce angina and congestive symptoms of shortness of breath or edema
Paroxysmal atrial fibrillation is the episodic occurence of the arrhythmia  Episodes may occur with sleep or with exercise

Diagnosis: 

Electrocardiogram
- absence of P waves
- unorganized electrical activity in their place
- irregularity of R-R interval due to irregular conduction of impulses to the ventricles

Causes:

- Arterial hypertension
- Mitral valve disease (e.g. due to rheumatic heart disease or mitral valve prolapse)
- Heart surgery
- Coronary heart disease
- Excessive alcohol consumption ("binge drinking" or "holiday heart")
- Hyperthyroidism
- Hyperstimulation of the vagus nerve, usually by having large meals

Treatment

Rate control by 
Beta blockers (e.g. metoprolol)
Digoxin
Calcium channel blockers (e.g. verapamil)

Rhythm control

Electrical cardioverion by application of a DC electrical shock
Chemical cardioversion is performed with drugs eg amiodarone

Radiofrequency ablation : uses radiofrequency energy to destroy abnormal electrical pathways in heart tissue It is used in recurrent AF

In confirmed AF, anticoagulant treatment is a crucial way to prevent stroke

Atrial flutter

Atrial flutter is a regular, rhythmic tachycardia originating in the atria. The rate in the atria is over 220 beats/minute, and typically about 300 beats/minute

he morphology on the surface EKG is typically a sawtooth pattern.

The ventricles do not beat as fast as the atria in atrial flutter

Supraventricular tachycardia

apid rhythm of the heart in which the origin of the electrical signal is either the atria or the AV node
it is important to determine whether a wide-complex tachycardia is an SVT or a ventricular tachycardia, since they are treated differently

Sick sinus syndrome : a group of abnormal heartbeats (arrhythmias) presumably caused by a malfunction of the sinus node, the heart's "natural" pacemaker.

Ventricular fibrillation

is a cardiac condition which consists of a lack of coordination of the contraction of the muscle tissue of the large chambers of the heart. The ventricular muscle twitches randomly, rather than contracting in unison, and so the ventricles fail to pump blood into the arteries and into systemic circulation.

Ventricular fibrillation is a medical emergency: if the arrhythmia continues for more than a few seconds, blood circulation will cease, as evidenced by lack of pulse, blood pressure and respiration, and death will occur. Ventricular fibrillation is a cause of cardiac arrest and sudden cardiac death
 

Polycystic kidney disease

Characterized by the formation of cysts and partial replacement of renal parenchyma.
Genetic transmission: autosomal dominant.
Clinical manifestations:

 hypertension, hematuria, palpable renal masses, and progression to renal failure. Commonly associated with berry
aneurysms.