Rain drop pigmentation is seen in
Chronic lead poisoning
Chronic Arsenic poisoning
Chronic Mercury poisoning
All of the above
chronic arsenic exposure from occupations for polonged periods 1-20 years may develop diffuse pigmentation predominant over trunk and is superimposed by 2-10mm macules of depigmentation producing characteristic rain drop appearence. IADVL textbook of dermatology, disorders of pigmentation page 786
Skin lesions and disorders of pigmentation