Pelizaeus–Merzbacher disease is an X-linked neurological disorder that damages oligodendrocytes in the central nervous system. It is caused by mutations in proteolipid protein 1 (PLP1), a major myelin protein. It is characterized by a decrease in the amount of insulating myelin surrounding the nerves (hypomyelination) and belongs to a group of genetic diseases referred to as leukodystrophies. Signs and symptoms
The hallmark signs and symptoms of Pelizaeus–Merzbacher disease include little or no movement in the arms or legs, respiratory difficulties, and characteristic horizontal movements of the eyes left to right.The onset of Pelizaeus–Merzbacher disease is usually in early infancy. The most characteristic early signs are nystagmus (rapid, involuntary, rhythmic motion of the eyes) and low muscle tone. Motor abilities are delayed or never acquired, mostly depending upon the severity of the mutation. Most children with Pelizaeus–Merzbacher disease learn to understand language, and usually have some speech. Other signs may include tremor, lack of coordination,  involuntary movements, weakness, unsteady gait, and over time, spasticity in legs and arms. Muscle contractures often occur over time. Mental functions may deteriorate. Some patients may have convulsions and skeletal deformation, such as scoliosis, resulting from abnormal muscular stress on bones. Cause
Pelizaeus–Merzbacher disease is caused by X-linked recessive mutations in the major myelin protein proteolipid protein 1 (PLP1). This causes hypomyelination in the central nervous system and severe neurological disease. The majority of mutations result in duplications of the entire PLP1 gene.
Fixed drug reactions,  are common and so named because they recur at the same site with each exposure to a particular medication. Medications inducing fixed drug eruptions are usually those taken intermittently. Signs and symptoms
A painful and itchy reddish/purple patch of skin that occurs in the same location with repeated exposures to the culprit drug is the classic presentation of a fixed drug reaction. The lips, genitals, and hands are often involved. Cause
Medications that are commonly implicated as a cause of fixed drug eruptions include the following:

Cetirizine
Ciprofloxacin
Clarithromycin
Cotrimoxazole
Doxycycline
Fluconazole
NSAIDs (e.g., ibuprofen, etoricoxib, naproxen)
Phenytoin
Pseudoephedrine
Trimethoprim

See also
Drug eruption
List of cutaneous conditions
List of human leukocyte antigen alleles associated with cutaneous conditions
Stevens–Johnson syndrome

References


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