Lysosomal (lipid) storage diseases
- Genetic transmission: autosomal recessive.
- This group of diseases is characterized by a deficiency of a particular lysosomal enzyme. This results in an accumulation of the metabolite, which would have otherwise been degraded by the presence of normal levels of this specific enzyme.

Diseases include:
Gaucher’s disease
(1) Deficient enzyme: glucocerebrosidase.
(2) Metabolite that accumulates: glucocerebroside.
(3) Important cells affected: macrophages.

Tay-Sachs disease
(1) Deficient enzyme: hexosaminidase A.
(2) Metabolite that accumulates: GM2 ganglioside.
(3) Important cells affected: neurons.
(4) Symptoms include motor and mental deterioration, blindness, and dementia.
(5) Common in the Ashkenazi Jews.

Niemann-Pick disease
(1) Deficient enzyme: sphingomyelinase.
(2) Metabolite that accumulates: sphingomyelin.
(3) Important cells affected: neurons.

Nephrolithiasis, urolithiasis

Formation of calculi (calcium stones) in the kidney (nephrolithiasis) or urinary tract (urolithiasis).
Commonly associated with hyperparathyroidism.
Signs and symptoms 

urinary tract obstruction, severe pain, and pyelonephritis.

Note: an enlarged prostate can also cause urinary tract obstruction in males.

Seborrheic dermatitis is a scaly dermatitis on the scalp (dandruff) and face.
 - due to Pitysporium species
 - can be seen in AIDS as an opportunistic infection

1. Human papillomavirus types 6 and 11 → condyloma acuminta (venereal warts).
2. Molluscum contagiosum is characterized by a bowl shaped lesion filled with keratin, the latter containing the viral inclusions (molluscum bodies) in the squamous cells. 

Characteristics of Immunoglobulin subclasses

I. Ig G:

(i) Predominant portion (80%) of Ig.

(ii) Molecular weight 150, 000

(iii) Sedimentation coefficient of 7S.

(iv) Crosses placental barrier and to extra cellular fluid.

• (v) Mostly neutralising effect. May be complement fixing.

(vi) Half life of 23 days.

2.IgM :

(i) Pentamer of Ig.

(ii) Molecular weight 900, 000

(iii) 19S.

(iv) More effective complement fixation and cells lysis

(v) Earliest to be produced in infections.

(vi) Does not cross placental barrier.

(vii) Halflife of 5 days.

3. Ig A :

• Secretory  antibody. Found in intestinal, respiratory secretions tears, saliva and urine also.
• Secreted  usually as a dinner with secretory piece.
• Mol. weight variable (160,000+)
• 7 S to 14 S.
• Half life of 6 days.

4.Ig D :

• Found in traces.
• 7 S.
• Does not cross placenta.

5. Ig E

• Normally not traceable
• 7-8 S (MoL weight 200,000)
• Cytophilic antibody, responsible for some hypersensitivity states,

Diseases from Str. pyogenes (Group A strep)

1.  Streptococcal pharyngitis.  Most frequent Group A infection.  Throat has gray-white exudate.  Infection may become systemic into blood, sinuses, jugular vein, meninges.  In less than a week the M-protein and capsule production decrease, and transmission declines.

2.  Skin infections, such as impetigo.  Especially in children.  Different M-proteins than in pharyngitis.  Skin infections associated with edema and red streaking (characteristic).

3.  Necrotizing fasciitis/myositis.  Infection of deeper tissue advances despite antibiotics.

4. Scarlet fever.  Caused by phage-associated erythrogenic toxin-producing strains.  Toxins cause cardiac, renal, and other systemic failures.  Rash is very red with a sand-papery feel and shedding of superficial skin.

5.  Toxic Shock Syndrome.  Parallels the toxic shock caused by TSST-carrying Staph. aureus.

6.  Non-suppurative, post-infection diseases. 

Rheumatic fever (myocarditis, cardiac valve disease, polyarthralgia, rashes.  Occurs two  weeks after a pharyngeal infection)

Glomerulonephritis (Occurs two weeks after pharyngeal or skin infections.  Often due to immunologic reaction to M-protein type 12)