These mutations in the PEX7 gene generally lead to rhizomelic chondrodysplasia punctata type 1- which impairs development of many parts of the body. Refsum disease is inherited in an autosomal recessive pattern, meaning that it requires both copies of the mutation to inherit the disease. Diagnosis
Histopathologic examination of the skin from a suspected patient commonly shows hyperkeratosis, hyper-granulosis and acanthosis. The presence of cells in the basal and suprabasal layers of the epidermis containing variably sized vacuoles with accumulated lipids is pathognomonic for the disease. Classification
Adult Refsum disease may be divided into the adult Refsum disease 1 and adult Refsum disease 2 subtypes. The former stems from mutations in the phytanoyl-CoA hydroxylase (PAHX aka PHYH) gene, on the PHYH locus at 10p13 on chromosome 6q22-24. It was initially believed this was the sole mutation; however 55% of cases are now attributed to mutations in other genes.Refsum disease 2 stems from mutations in the peroxin 7 (PEX7) gene. This mutation on the PEX7 gene is also on chromosome 6q22-24, and was found in patients presenting with accumulation of phytanic acid with no PHYH mutation.Adult Refsum disease should not be confused with infantile Refsum disease, a peroxisome biogenesis disorder resulting from deficiencies in the catabolism of very long chain fatty acids and branched chain fatty acids (such as phytanic acid) and plasmalogen biosynthesis.
Malassezia folliculitis or Pityrosporum folliculitis,  is a skin condition caused by infection by Malassezia (formerly Pityrosporum) yeast. : 314 The skin of the upper trunk area including the back, chest, arms and sometimes the neck is often affected and this condition is often seen in young to middle aged adults, although it has been known to occur in adults well into their sixties, and can also be found on the lower extremities as well. Its diagnosis is based on the pruritic (itchy) papulopustules found in a follicular pattern in these regions.Pustules are caused by an overgrowth of the yeast (a type of fungus) Malassezia furfur (Pityrosporum ovale), which plugs the follicles. M. furfur is lipophilic, requiring fatty acids like what is present in oily skin to proliferate. It has been shown that Malassezia yeast grows by consuming fatty acids with carbon chain lengths C11 to C24. Pityrosporum is part of the normal skin flora, but overgrows in certain conditions. Overgrowth is associated with oily skin, humidity or other pre-existing dermatologic conditions such as seborrheic dermatitis and severe dandruff. See also
Skin lesion
List of cutaneous conditions


== References ==