Earlier posters asked about porphyria symptoms so I thought it might be useful to outline the symptoms of Acute Intermittent Porpyhria, as described in Purple Secret. AIP is the most common form of the disease and one of the main candidates for the malady in the Royal Stuarts.
From Purple Secret (1998) by John C.G. Rohl, Martin Warren and David Hunt. p 244-245:
Acute Intermittent Porphyria (AIP) is the most common of the inherited porphyrias and is caused by a deficiency in the enzyme porphobilinogen deaminase (PBGD). A deficiency in this enzyme leads to the accumulation of the early pathway intermediates porphilobinogen (PBG) and ALA, which are excreted in the urine of patients during an attack. The excretion of PBG can give rise to the presence of coloured urine, usually red or brown. More often, the colour of urine develops with time after it is left to stand. AIP is normally triggered by factors such as diet, hormones and drugs. The disorder is generally expressed after puberty and with a higher incidence in women than in men, perhaps reflecting the greater fluctuation in hormone levels.
There have been a number of clinical studies on the incidence of the symptoms of AIP. In all cases, around 90 per cent of patients suffer from abdominal pain, with a majority also suffering from vomiting and constipation. Patients were also found to suffer from limb, head, neck or chest pains, muscle weakness, hypertension and tachycardia and to display mental symptoms. In addition, some patients reported convulsions, sensory loss, breathing difficulties and fever. The abdominal pains are often severe enough to warrant surgical exploration. If this is accompanied by a barbiturate-based anaesthetic, it often makes the AIP more acute and can lead to death. In severe cases, the urine of the patient has a port-wine colour due to the concentration of excreted PBG and its chemical derivatives.
Patients can become hypersensitive, anxious, restless, insomniac, paranoic or depressed and, in some cases, have been labelled as hysterical. The high incidence of AIP patients in psychiatric institutions shows how easy it is to misdiagnose the disorder. All of the major symptoms of AIP are thought to be caused by the effect of the early pathway intermediates on the nervous system, causing it to function incorrectly. However the exact cause and site of the dysfunctions are still unknown. AIP is thought to occur in about one in ten thousand of the population, although the actual frequency may be even higher than this.
One of the problems in assessing the level of occurrence of AIP is that about 90 per cent of people who carry the defective gene for AIP never display any symptoms. The reasons why so many carriers remain asymptomatic is unclear. One point which is certain is that AIP can be induced in carriers by a number of factors, including certain drugs, alcohol and hormones. The main effect of these factors is to increase the level of activity of the enzyme which makes ALA, the starting point of haem biosynthesis. The increased concentration of ALA leads to an increase of flow of intermediates through the haem pathway, an increase which most healthy individuals can cope with. However, AIP patients have a reduced level of PBGD and thus the pathway in these individuals cannot cope with the increase in rate and a bottleneck forms at this point. An increase in ALA and PBG occurs and these elevated levels consequently lead to the neurophysiological problems associated with an AIP attack. Progesterone and oestrogen, endocrine hormones associated with women’s menstrual cycles, are also known to influence AIP attacks. On the whole, AIP is rarely manifested before puberty and there is a drop in the level of AIP attacks in post-menopausal women. Overall, AIP is more common in women than men (at a ratio of three women to two men suffer with AIP) and women are more susceptible to AIP attacks at the start of their period. A number of women AIP sufferers have reported a periodicity of attacks which reflects their menstrual cycle. Certain contraceptive pills also cause attacks in women carriers of the disorder.
Poor diet is also a major influence on AIP attacks. In general it is thought that a low caloric diet can increase the likelihood of an attack, and, consequently, AIP sufferers are more likely to precipitate an attack if they go on a crash diet.