Pityriasis alba is a skin condition, a type of dermatitis, commonly seen in children and young adults as dry, fine-scaled, pale patches on the face. It is self-limiting and usually only requires use of moisturizer creams.The condition is so named for the fine scaly appearance initially present (pityriasis), and alba (Latin for white) refers to the pallor of the patches that develop. The patches are not totally depigmented. Signs and symptoms
The dry scaling appearance is most noticeable during the winter as a result of dry air inside peoples homes. During the summer, tanning of the surrounding normal skin makes the pale patches of pityriasis alba more prominent.Individual lesions develop through 3 stages and sometimes are itchy:

Raised and red – although the redness is often mild and not noticed by parents
Raised and pale
Smooth flat pale patchesLesions are round or oval raised or flat, of 0.5–2 cm in size although may be larger if they occur on the body (up to 4 cm), and usually number from 4 or 5 to over 20. The patches are dry with very fine scales. They most commonly occur on the face (cheeks), but in 20% appear also on the upper arms, neck, or shoulders.The diagnostic differential should consider tinea and vitiligo amongst other causative factors. Cause
Any dermatitis may heal leaving pale skin, as may excessive use of corticosteroid creams used to treat episodes of eczema. The hypopigmentation is due to both reduced activity of melanocytes with fewer and smaller melanosomes.The cause of pityriasis alba is not known.
Hypochloremia (or Hypochloraemia) is an electrolyte disturbance in which there is an abnormally low level of the chloride ion in the blood. The normal serum range for chloride is 97 to 107 mEq/L. It rarely occurs in the absence of other abnormalities. It is sometimes associated with hypoventilation. It can be associated with chronic respiratory acidosis. If it occurs together with metabolic alkalosis (decreased blood acidity) it is often due to vomiting. It is usually the result of hyponatremia or elevated bicarbonate concentration. It occurs in cystic fibrosis. References


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