A. Sexually Transmitted infections (STIs)
Sexually transmitted diseases, (infections) (STIS) are a group of infection.
Sexually transmitted through sexual contact are-syphilis, Gonorrhea, chanoroid, Donovanosis, Herpes simplex, Hepatitis B & HIV
1) Syphilis- This treponemal infection is known over the years for its ability to present in many different ways. Being a potentially serious infection, every doctor has to be on guard not to miss this easily treatable condition. It is caused by the spirochete, Treponema pallidum. It may be acquired as a sexually transmitted disease or may be transferred transplacentally as congenital syphilis.
2) HIV infection & AIDS-
Transmission of HIV infection-In India, hetero sexual intercourse is responsible for transmission of 80% of cases Intravenous drug abuse, homosexuality and blood and blood product transfusions are responsible for a small but substantial number. Transplacental transfer, intranatal trauma & secretion of virus in the breast milk are responsible for infection of children born of HIV Infected mother.
Patient profile- Spread of HIV infection in a community shows 3 stages. In the first stage only persons with high-risk activity like having unsafe sex with multiple partners are involves. In the second phase, spouses (mostly housewives) or partners of individuals with high-risk activity are affected. In the third phase, the disease appears in the children born of HIV infected mothers.
Prevention of STIs
This has assumed great importance in recent times with the emergence of HIV infection. The various measures that can be advised include- 1.Abstinence from sex-impossible for most people.
2.Avoid sex with commercial sex workers as the chance of their being a carrier for STIs esp. HIV infection, is very high(60%of commercial sex workers in Mumbai are HIV positive.)
Restrict to one sexual partner. Avoid casual sex or sex with someone whose antecedents are unknown.
If you must, then use a good quality Condom every time.
After sex, pass urine after intercourse a wash gentitalia as soon as possible with plenty of water & soap.
Sex education forms an essential part of prevention of STIs as it is only through such discussion that advice regarding condom usage can be disseminated to the young.                   

B. ACNE VULGARIS & ROSACEA
Acne Vulgaris- This condition is so common in adolescence that it may be considered physiological to have a few lesions of acne vulgaris at some time during adolescence and young adulthood.
Patient profile- Adolescents and young adults are typically affected. Occasionally acne may persist in middle. Age or may rarely begin during middle age. Men are more severely affected than women. Contact with oil & oily preparations (e.g. oil based make up) tend to aggravate acne. Hot & humid environment & resultant sweating may exacerbate acne. Premenstrual flare of acne in women is well known.
Rosacea- A facial eruption of middle aged men & women, rosacea is quite unrelated to acne vulgaris. Facial flushing is a forerunner of rosacea in many instances.
Patient profile- Although women are more commonly affected rosacea occurs in males as well. Premenopausal or menopausal episodes of flushing may predispose to the occurrence of rosacea.

C. Disease due to Fungi-
1 Tinea Versicolor      2 Ringworm of skin 
3 Ringworm of nails   4 Candidiasis
Tinea Versicolor-A common infection caused by overgrowth of the lipophilic fungus Pityrosporum orbicular, which is also a normal inhabitant of hair follicles.  
Patient profile-Young adults and adolescents are typical patients. It is more common in males. Oily skin and sweating predisposes to this infection. Ache vulgaris and seborrheic dermatitis are common associations
Candidiasis- This is an opportunistic yeast infection caused by Candida albicans and occasionally by other Candida species. The yeast proliferates whenever a conductive (i.e. hot & humid) environment exists with or without lowered body resistance 
Patient profile-overweight adults & chubby infants are common
victims. Diabetes mellitus is a common predisposing factor in
adults. Affection of toe webs and finger webs is common in occupations involving wet work e.g. Housemaids A tendency to   sweat excessively may be a contributory factor.                
                                                                 
D. Bacterial Infection –Some are as follows
1) Impetigo 2) Ecthyma 3) Folliculitis 4) Furuncle & Carbuncle

Impetigo- This is a superficial bacterial infection caused by staphylococci or streptococci.
Patient profile – Young children are typically affected, Infants, especially neonates, are susceptible to the serious bullous variant of this disease. Epidemics amongst neonates in nurseries are known lesions are a symptomatic.                  

E. Diseases due to viruses-
1) Molluscum contagiosum 2) Herpes simplex 3) Herpes zoster 4) Verrucae

Molluscum contagiisum- A common cutaneous viral infection seen principally in children & occasional as a sexually transmitted disease in adults, it is caused by the molluscum virus (a DNA virus of the pox group)
Patient profile-Usually young children acquire this infection by skin to skin contact while playing. Adults may acquire it through sexual or non-sexual contact. Occurrence of wide spread lesions of molluscum contagiosum in an adult is a marker of      immunodeficiency e.g. HIV disease, leukemia.  
                           
F. Disease due to Arthropod Parasites-

Scabies-This is a common ectoparasitic infection caused by the mite Sarcoptes scabiei that is transmitted by close body contact.
Patient profile- Affects children, more frequently than young adults. Overcrowding facilitates transmission
Clinical features- severe pruritus, that gets worse at night, is a rule. More than one family member is usually affected. Commonly scabies is transmitted from one family to another family through young children. Occasionally in adults, it is transmitted through sexual contact.                                                               

G. Pigmentary Disorder
1) ALBINISM, 2) VITILIGO 3) PUVA THERNG
4) MELASMA (Pregnancy mask)

VITILIGO- This pigmentary disorder of unknown cause is characterized by depigmented or hypopigmented patches that result from absence or reduction in melanocytes.
Clinical profile-About 1-2%of the general population has vitiligo. Vitiligo begins commonly in the 2^nd to 4^th decade. It is less common in children & the elderly. Both sexes are affected equally.

Melasma (Pregnancy mask)-
This is the commonest cause of hyperpigmentaion of face in women.
Patient profile- Although most patients are women, men are occasionally affected. Hormonal changes are thought to underlie this disorder which frequently appears in the latter half of pregnancy or postpartum, oral contraceptives have also been implicated in its causation in some cases.