ALAD deficiency porphyria is a very rare type of porphyria. The disorder results from low levels of the enzyme responsible for the second step in heme production. Heme is a vital molecule for all of the body's organs. It is a component of hemoglobin, the molecule that carries oxygen in the blood. ALAD deficiency porphyria is a subtype of porphyria. Signs and symptoms, which have varied in the few people diagnosed with ALAD deficiency porphyria, include weak muscle tone (hypotonia) in infancy, acute attacks of abdominal pain and muscle weakness, and muscle pain or numbness. These signs and symptoms can begin in infancy, childhood, or adulthood.