The skin pattern most commonly associated with SJS is widespread, often joined or touching (confluent), papuric spots (macules) or flat small blisters or large blisters which may also join. These occur primarily on the torso.SJS, TEN, and SJS/TEN overlap can be mistaken for erythema multiforme. Erythema multiforme, which is also within the SCAR spectrum, differs in clinical pattern and etiology. Prevention
Screening individuals for certain predisposing gene variants before initiating treatment with particular SJS-, TEN/SJS-, or TEN-inducing drugs is recommended or under study. These recommendations are typically limited to specific populations that show a significant chance of having the indicated gene variant since screening of populations with extremely low incidences of expressing the variant is considered cost-ineffective. Individuals expressing the HLA allele associated with sensitivity to an indicated drug should not be treated with the drug. These recommendations include the following. Before treatment with carbamazepine, the Taiwan and USA Food and Drug Administrations recommend screening for HLA-B*15:02 in certain Asian groups. This has been implemented in Taiwan, Hong Kong, Singapore, and many medical centers in Thailand and Mainland China. Before treatment with allopurinol, the American College of Rheumatology guidelines for managing gout recommend HLA-B*58:01 screening. This is provided in many medical centers in Taiwan, Hong Kong, Thailand, and Mainland China. Before treatment with abacavir, the USA Food and Drug Administration recommends screening for HLA-B*57:01 in Caucasian populations. This screening is widely implemented. It has also been suggested that all individuals found to express this HLA serotype avoid treatment with abacovir.
Nitisinone, sold under the brand name Nityr and Orfadin among others, is a medication used to slow the effects of hereditary tyrosinemia type 1 (HT-1). Uses
Nitisinone is used to treat hereditary tyrosinemia type 1 (HT-1) in patients from all ages, in combination with dietary restriction of tyrosine and phenylalanine.Since its first use for this indication in 1991, it has replaced liver transplantation as the first-line treatment for this ultra rare condition. Adverse effects
The most common adverse reactions (>1%)  for nitisinone are elevated tyrosine levels, thrombocytopenia, leukopenia, conjunctivitis, corneal opacity, keratitis, photophobia, eye pain, blepharitis, cataracts, granulocytopenia, epistaxis, pruritus, exfoliative dermatitis, dry skin, maculopapular rash and alopecia.has several negative side effects; these include but are not limited to: bloated abdomen, dark urine, abdominal pain, feeling of tiredness or weakness, headache, light-colored stools, loss of appetite, weight loss, vomiting, and yellow-colored eyes or skin. Mechanism of action
The mechanism of action of nitisinone involves inhibition of 4-Hydroxyphenylpyruvate dioxygenase (HPPD). This is a treatment for patients with Tyrosinemia type 1 as it prevents the formation of 4-Maleylacetoacetic acid and fumarylacetoacetic acid, which have the potential to be converted to succinyl acetone, a toxin that damages the liver and kidneys. This causes the symptoms of Tyrosinemia type 1 experienced by untreated patients.Alkaptonuria is caused when an enzyme called homogentisic dioxygenase (HGD) is faulty, leading to a buildup of homogenisate. Alkaptonuria patients treated with nitisinone produce far less HGA than those not treated (95% less in the urine),  because nitisinone inhibits HPPD, resulting in less homogenisate accumulation.