Final answer:
The student's description of depigmented macules that glow white under a Wood's lamp likely indicates a diagnosis of vitiligo, which is confirmed by the distinct fluorescence of affected skin areas when exposed to ultraviolet light.
Step-by-step explanation:
The presentation of well-demarcated, depigmented macules on hands and face, which glow white under a Wood's lamp, is a hallmark of vitiligo. This condition involves the loss of melanocytes, the cells responsible for producing melanin, which gives skin its color. The Wood's lamp examination is useful in diagnosing conditions of depigmentation by causing affected areas to fluoresce due to the contrast between normal and depigmented skin. If a spot on the skin is affected by vitiligo, it stands out under the lamp's ultraviolet light.
Other conditions with distinctive dermatological signs include xeroderma pigmentosum, which is characterized by skin lesions due to a deficiency in DNA repair mechanisms after UV exposure, and tinea infections (like ringworm), which can also fluoresce under a Wood's lamp if caused by certain fungi. It is important to differentiate between these conditions, as treatments vary widely.