Leukemia (Blood Cancer)

 

Human scabies is an intensely pruritic skin infestation caused by the host-specific mite Sarcoptes scabies hominins. Scabies is a global public health problem affecting persons of all ages races and socioeconomic groups, the disease remains common primarily because of diagnostic difficulty, inadequate treatment of patients and their contacts, and improper environmental control measures prevalence of scabies is higher in children and sexually active individuals than in another person transmission of scabies primarily occur through direct skin to skin contact and for this reason, it is commonly seen among sexually active individuals less frequently.

The disease can spread by indirect contact through fomites such as infested bedding or clothing a person infested with mites can spread the disease even if they are asymptomatic and there may be a prolonged period between the primary infection and symptom onset, now let's discuss the life cycle of the mite and pathogenesis of the disease, human scabies mite is an obligate parasite that completes its entire life cycle on humans and only the female mite infects the human, it is large enough to be seen with the naked eye the mite has four pairs of legs and it crawls at a rate of 2.5 centimeters per minute it is unable to fly or jump the mite does not penetrate deeper than the superficial layer of the epidermis, the stratum corneum it can survive on bedding clothes or other surfaces at room temperature for about two to three days at temperatures below 20 degrees Celsius the mite is unable to move however it can survive such temperatures for extended periods.  

The other variants of scabies mite can cause an infestation in other mammals such as dogs; cats, pigs, and horses, these variants can cause irritation in human skin as well however they are unable to reproduce in humans so they cause only transient dermatitis. This image shows the complete life cycle of the scabies mite the female mite lays eggs inside the burrow she made within the stratum corneum as you can see in this picture then the eggs hatch within two to three days to form larvae which have three pairs of legs then the larvae mature into nymphs which have four pairs of legs, finally the larger nymphs become adults mating takes place only once and the female is fertile for the rest of her life, the mature female makes a serpentine burrow in the stratum corneum using proteolytic enzymes to lay eggs to start a new cycle there are two main types of scabies classic scabies and crusted scabies

Classic scabies is the predominant type and typically 10 to 15 mites live in the host there is little evidence of infection exists during the first month however after four weeks and with subsequent infections, a delayed type hypersensitivity reaction occurs against mites eggs, larvae, and feces with re-infestation the sensitized individual may develop a rapid response the resultant skin eruption and associated intense parities are the hallmarks of classic scabies.

Crusted scabies is a distinctive and highly contagious form of the disease in this variant hundreds to millions of mites infest the host individual who is usually immuno-compromised elderly or physically or mentally impaired risk factors for scabies include young age presence of many children in the household par housing sharing clothes and towels and irregular use of showers.

Now let's discuss the clinical presentation of scabies patients complain of intense parities that are worse at night, lesions are distributed predominantly in the following areas in adult’s flexor aspects of the wrists inter-digital web spaces of the hands actually elbows, waist, buttocks, and genitalia, peritic, papules and vesicles on the scrotum and penis in men and a really in women are highly characteristic infants and young children may develop lesions diffusely but unlike in adults lesions are standard on the face, scalp, neck, palms, and soles in immuno-compromised individuals all cutaneous sites are susceptible for lesions.

Physical examination findings include primary and secondary lesions. Primary lesions are the first manifestations of the infestation and typically include small papules vesicles and burrows, burrows are a pathognomonic sign that represents the intra-epidermal tunnel created by the moving female mite they appear as serpiginous thread-like elevations in the superficial epidermis ranging from 2 to 10 millimeters in length these may not be readily apparent and must be actively sought a black dot may be seen at one end of the burrow indicating the presence of a mite high yield locations for burrows include the following web spaces of the fingers flexor surfaces of the wrists,  elbows, axially belt line, feet scrotum and men and a rarely in women erythematous papules and vesicles are also seen in typical distributions in adults they range from 1 to 3mm in size.  

The vesicles are discrete lesions with clear fluid papules that rarely contain mites and most likely represent the hypersensitivity reaction they are commonly seen on the shaft of the penis in men and rarely in women, scabies nodules occur in about 7 to 10 cases, particularly in young children mites are rarely found within these nodules crusted scabies manifests with marked thickening and crusting of the skin, the lesions are often hyper-keratic and cover larger skin areas marked scaling is common pruritus may be minimal or absent nail dystrophy and scalp lesions may also be present. Secondary scabies lesions result from scratching secondary infection and host immune response against mites in their products characteristic findings include the following excoriations Post inflammatory hyperpigmentation, erythroderma, and widespread eczema and honey-colored crusting diagnosis of scabies can often be made clinically in patients with a peritic rash and characteristic linear burrows and the diagnosis is confirmed by light microscopic identification of mites larvae and ova and skin scrapings in rare cases mites are identified in biopsy specimens obtained to rule out another dermatitis clinically inapparent.

Infection can be detected by amplification of sarcoptes DNA by polymerase chain reaction (PCR) in addition elevated IGE titers and eosinophilia can also be seen treatment of scabies include administration of scabicidal agents such as permethrin,  indane and ivermectin in addition appropriate anti-microbial agents may be required if a secondary infection has developed itching may persist up to one month even following successful treatment this may be partially alleviated with an oral antihistamine such as hydroxyzine, hydrochloride in case of nodular scabies intranodular injection of dilute corticosteroids may be needed patients with crusted scabies should be advised to remove excess scale to allow better penetration of the topical agents and to decrease the burden of infestation, this can be achieved with warm water soaks followed by application of a keratolytic agent such as 5 salicylic acid and petroleum because of the heavy mite burden patients with crusted scabies may require repeated application of topical agents with simultaneous use of oral agents as far as the prevention is concerned all household members and close personal contacts older than two months and not pregnant should be treated for scabies even if they are asymptomatic advise them to launder clothing bed linens and towels in hot water and machine dry them items that cannot be washed may be dry cleaned or sealed in plastic bags and all carpets and furniture should be vacuumed and the vacuum bags should be immediately discarded.

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