Parasitic Infestations😍

Scabies

Definition and Cause:

• Common parasitic infestation

• Caused by Sarcoptes scabiei variety hominus

Transmission:

• Through fomites

Occurrence:

• Usually in overcrowded areas

• Areas receiving less sunlight

Mite Characteristics:

• Typically 10-12 mites in normal patient

• Female mite
• responsible for infestation
• digs a tunnel → burrow

Classical Lesion

• Scabies-specific skin lesion: a burrow

• Burrow: track laid by female mite into skin

• Tract laid into stratum corneum
• Can extend deep up to stratum malpighi

• Wavy linear tract

• Female mite lays eggs at end of tunnels

Clinical Presentation:

• History:
• Positive family history (other family members affected)
• Nocturnal itching (more at night)
• Produce itching after 3-4 weeks
• Itching due to allergic reaction
• Reinfection: Immediate symptoms

• Lesions:
• Excoriated papules
• Secondary infections
• Most importantly: burrows

Location/Distribution:

Diagnosis:

• Mostly clinical

• Investigations not typically done

• If smear made from burrow, can see:
• Female mites
• Eggs
• Fecal material (scybala)

• Very classical location

• Affects face in infants

• Circle of Hebra
• Imaginary circle
• Includes:
• Interweb spaces
• Flexure area of the wrist
• Axilla
• Mammary area
• Groins

Treatment:

• General Measures (Very Important):
• Treat
• family members
• fomites (linens, bedding, clothes)
• Repeat application of scabicidal drug
• May not kill eggs
• Eggs form mites in a week's time

Drugs:

• Mnemonic:
• Ivare () Permit () cheyanam → Malathi () come with Sulfur () in Benze (benzyl)

Crusted Scabies or Norwegian Scabies:

• Most severe form

• Usually in patients with:
• Down syndrome
• Neurological abnormalities

• Typically in institutional settings

• Mnemonic: Norwegian → Normal allatha aalkk → downs and mental retard

• Patients cannot itch (normal itching breaks down burrows)
• Burrows stay and form crusts
• Heaps of crusts

• Millions of mites present (normally 10-12)

• Hyperkeratotic crusted lesions
• Present all over body
• Predominantly on hands and feet

Treatment:

• Topical treatment

• Oral ivermectin

• Keratolytics

• Treatment needs to be repeated

Atypical Scabies:

• Infantile Scabies:
• Face affected
• normally not affected due to protective sebum
• but infants lack sebum
• Infants can show vesicular lesions (cannot itch)

• Animal Scabies:
• Shows no burrows
• Humans can get from animals

• Genital Scabies:
• Considered an STI (sexually transmitted infection)
• Look for history of sexual transmission

• Nodular Scabies:
• Usually in axilla and groin
• Due to antigen hypersensitivity
• Persistent nodular lesions in these areas

Pediculosis

• Causes and Types:
• Caused by Pediculus humanus:
• Capitis (head lice)
• Corporis (body lice)
• Caused by Pthirus pubis (pubic lice)

Pediculosis Capitis (Head Lice):

• Commonly seen as lice in school-going children

• More common in females (long hair)

Clinical Presentation:

• Lice and nits

• Itching on scalp

• Other friends/students in class may be affected

Complications:

• Itching leads to secondary infection, crusting
• Eventually matting of hair
• Called Plica Polonica (feature of pediculosis capitis)
• Mnemonic: Peen karanam Mat (Matting) il kidann thala chorinj
• Polonica (Plica Polonica) poi

Recurrent pediculosis capitis

• Recurrent secondary infection
• Leads to cervical lymphadenopathy
• Most common reason for
• recurrent folliculitis or
• lymphadenopathy in school-going girl

Pediculosis Corporis (Body Lice):

• Mnemonic: Morbid (homeless) ayttulla alkk → morbus aerorum

• Also called Vagabond's Disease

• Seen in destitutes/homeless individuals
• Do not change clothes or bathe for many days
• Leads to infestation

• Mite Location:
• Mites in seams of clothing
• Come to skin at night, take meal, go back (leading to itching)

Clinical Presentation:

• Itchy lesions on trunk

Morbus Aerorum

• Post-inflammatory hyperpigmentation left by bites of mites

• Mites take blood meal, leaving hyperpigmentation on trunk of destitutes/homeless people

• Morbus Aerorum is feature of pediculosis corporis

Pediculosis Pubis (Pubic Lice):

• Considered an STI

• Rule out sexual history

• Caused by Pthirus pubis

• Clinical Presentation:
• Nits on genital hair, eyelashes, axilla
• Itching

Classical Lesion: 

• Maculae Ceruleae (bluish macules)
• "Ceruleae" means blue,
• "Maculae" means macule
• Bluish macules in genital area
• Mite takes blood meal, some extravasation of blood turns blue

Treatment for Pediculosis Pubis :

• Manual removal of lice nits on head (Vaseline can be used)
• Removal very important

• 1% Permethrin 
• for scabies 5% permethrin is used;
• S → 5
• for pediculosis 1% permethrin is required;
• P → 1

• Oral Ivermectin can also be used

Important Adverse Drug Reactions

1. Fixed Drug Eruption

well-demarcated, round or oval patches

• Description:
• Peculiar type of drug reaction
• Patient develops fixed morphology lesion at fixed place every time drug consumed → Recurrent

• Common Drugs:
• NSAIDs
• Co-trimoxazole
• Fluoroquinolones

• Clinical Presentation:
• History of headache or stomach ache
• Took antibiotic, developed well-defined, coin-shaped lesion
• Happens every time drug taken, at same site (e.g., trunk or genital area)
• Very well-defined lesion
• Usually erythematous plaque or macule
• Erosion can be seen in genital area

• Hypersensitivity Type:
• Type IV hypersensitivity

• Classical Feature:
• Rashes always heal with pigmentation
• Hyperpigmentation on lips is very classical

What is the diagnosis for a 40-year-old woman who experienced fever and joint pain, and subsequently developed a lesion on her nose a few days after taking NSAIDs?

A. Dengue
B. Chikungunya
C. Melasma
D. Fixed drug eruption

ANS

• Chikungunya → Chik sign
• Post-Recovery Sign
• Clinical Features: Fever, migratory arthritis.

2. Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN)

Description:

• Severe cutaneous adverse drug reactions

Classification based on Body Surface Area (BSA) Involved:

Alternate Name:

• Carbamazepine → SJS

• Oxcarbamazepine → SIADH

• TEN also called Lyell's Disease

Involvement:

• Skin

• Mucosa

• Systemic involvement may be present

• = two mucosa definitely involved (e.g., lips, genital mucosa, ocular mucosa)

Clinical Stages:

1. Prodrome (fever, malaise, constitutional symptoms)
• after drug

2. Purpuric lesions (trunk, limbs, hands, feet)
• spread as sheets of erythema

3. Skin shed off (necrolysis)

4. Severe erosions and crusting in mucosal areas

Pseudo Nikolsky positive

Complications:

• Many complications due to whole skin involvement

• Patient goes into:
• Hypothermia
• Hypocalcemia
• Septic shock

• Future complications, especially in eye area

• Patients can even die

Mortality Prediction:

• SCORTEN
• Predicts mortality in patients of TEN

• Score >5 → 90% chances of mortality

Parameters:

• Age

• Malignancy

• Presence of Tachycardia

• Body Surface Area (BSA) involved (initial surface of epidermal detachment)

• Three biochemical parameters
  (mnemonic BUG cause death in TENS):
• Bicarbonate
• Urea
• Glucose

Treatment:

• Dermatological emergency

• Keep patient in dermatological emergency ward

• Give fluids, antipruritics

• Do dressing, clean up mucosa

• Mostly conservative management

3. Drug-Induced Pigmentation

• Certain drugs can lead to skin pigmentation

Nail pigmentation causing drugs

• Phenothiazines
• Chlorpromazine
• Used for DM and DI
• S/E: SIADH, Disulfiram like reaction

• Chloroquine

• Minocycline

• Queen meena for magazine → put nail lacquer

Minocycline:

• Given for acne

• Leads to blue-black pigmentation on acne scars

• Black thyroid

• Due to deposition of iron chelates with minocycline

• Also leads to lupus-like reaction

• Mnemonic: Meena de mugath blue black vann

Hydroquinone:

• Commonly for melasma

• Overuse leads to Ochronosis

• Deep blue pigmentation on melasma lesions
• typically on malar area

• ⛔ homogentisic acid oxidase

• Leads to deposition of ochre bodies in skin

• Mnemonic: Homo (homogentisate) people → Malam (malasma) eduth Vellam (hydroquinone) ozhich → Ockkanich (ochronosis)

HCQS (Hydroxychloroquine):

Bleomycin:

• Anti-cancer drug

• Leads to flagellate pigmentation on body

• Mnemonic: Blew a horn on my back

 

Zidovudine:

• Given to HIV positive patients

• Typically leads to pigmentation of nails & skin

• Also Bone marrow suppression

• If hand only → Emtricitabine

• Mnemonic: Zidovudine → Seed in hand → Hyperpigmentation

Clofazimine:

• Prescribed in leprosy patients

• Typically leads to ichthyosis

• Also reddish-brown pigmentation

• Forms crystals deposited in skin

• Presence indicates regular medication

• Mnemonic: clofaziMeeen → Icthyosis

Amiodarone:

• Given for tachycardia and arrhythmias

• Leads to pigmentation on photo-exposed areas (face, dorsum of hands)