Ans: Incontinentia pigmenti ref - Incontinentia pigmenti - Wikipedia, the free encyclopedia & JAMA Network | Archives of Dermatology | The Skin Is Not the Predominant Problem in Incontinentia Pigmenti Many people in the past were misdiagnosed with a second type of IP, called IP2. This has now been given its own name - 'Hypomelanosis of Ito' (incontinentia pigmenti achromians). This has a slightly different presentation: swirls or streaks of hypopigmentation and depigmentation. It is NOT inherited. It does not inolve skin stages 1 or 2. ref - wiki (-:
Self Assessment Question Self Assessment Question New discoveries made possible by advances in molecular genetics have broadened our understanding of nontraditional inheritance. Match this disease with the appropriate genetic mechanism: a developmentally delayed 2-year-old has bilateral hypopigmented whorls on the upper extremities. A. Mitochondrial inheritance B. Mosaicism C. Genomic imprinting D. Sex chromosome imbalance E. Triplet repeat expansion disorder EXPLANATION: The mitochondrial genome originates only from the ovum and is therefore transmitted by the mother to her offspring of both genders. Mitochondrial disease involves mainly brain and muscle. Ragged red fibers seen on muscle biopsy are present in several inherited enzyme defects. Examples of mitochondrial inheritance include myoclonic epilepsy and ragged red fibers (MERF); mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS); and Leber hereditary optic neuropathy (LHON), a condition not associated with myopathy. Prader-Willi syndrome, which is characterized by hypotonia, obesity, hypogonadism, mental retardation, and characteristic hands, feet, and facies, is caused by a chromosomal deletion of 15q11-13 when the chromosome is of paternal origin. In some syndromes, such as Angelman syndrome, chromosomal deletion of maternal origin results in a syndrome characterized by a specific facies, happy disposition, mental retardation, bizarre movements, and seizures. More recently, cases of Prader-Willi syndrome have been found wherein there is no DNA deletion but both copies of chromosome 15 have been inherited from the mother; similarly, some cases of Angelman syndrome have been shown to have two copies of paternally derived chromosome 15. This suggests that it is the lack of part of paternal chromosome 15 that causes Prader-Willi syndrome and the lack of part of maternal chromosome 15 that causes Angelman syndrome. Some conditions have a more dynamic mutation that can continue to expand with errors in replication. These are called triplet repeat expansion disorders, and include fragile X syndrome, Huntington disease, and myotonic dystrophy. As the gene is further replicated and expanded, protein production ceases and clinical symptoms are expressed. Hypomelanosis of Ito is not thought to be inherited, but does display mosaicism in that about half of affected patients have two distinct cell lines of skin fibroblasts. Other examples of inherited mosaicism include higher functioning patients with trisomy 21, who may display some physical findings consistent with the syndrome but may not have as severe cognitive delay, as some cells have trisomy 21 and others do not. The answer is B. This may seem easy now...since we have gone through it many times ( the power of revision ;-) )
