Arsenic poisoning can occur through ingestion, inhalation, or skin absorption of arsenic compounds. Acute arsenic poisoning causes gastrointestinal symptoms like vomiting and diarrhea, while chronic exposure can lead to skin lesions, peripheral vascular disease, and cancer. Diagnosis is made through laboratory tests of urine, blood, hair, nails, and tissue samples, which detect elevated arsenic levels. Treatment for acute poisoning involves gastric lavage, administration of chelating agents like BAL, and supportive care, while chronic cases require removing the source of exposure and long-term chelation therapy along with symptom management. Autopsy findings may show inflammation of the gastrointestinal tract and liver congestion in acute deaths.