Cellulitis - Hair and Scalp
- Immunocompetent adults: Staphylococcus aureus and Streptococcus pyogenes. Staphylococcus aureus is the most frequent etiology in children and in purulent cellulitis.
- Immunocompromised individuals, including those with diabetes and decubitus ulcers: mixture of gram-positive cocci and gram-negative aerobes and anaerobes.
Fevers, chills, and malaise often precede the onset of cellulitis. Poorly defined borders, erythema, swelling, tenderness, and warmth characterize typical cellulitis lesions. In adults, the extremities are the most common sites affected. In more severe cases, additional clinical features may include vesicle and bulla formation, pustules, and necrosis. Complications are not common but can include glomerulonephritis, lymphadenitis, and subacute bacterial endocarditis.
A rising prevalence of MRSA has been identified as a pathogen of skin and soft tissue infections in otherwise healthy individuals lacking the aforementioned risk factors for cellulitis. MRSA should be considered for penetrating traumas, purulent infections, and in specific populations: athletes, children, prisoners, military service members, long-term care residents, and intravenous drug users. Other MRSA risk factors include recent admission to a health care facility, presence of an indwelling catheter, poor personal hygiene, and history of MRSA.
Note: Cellulitis virtually never occurs bilaterally at the same time. If redness and involvement of the legs are bilateral in a patient suspected to have cellulitis, consider an alternative diagnosis such as stasis dermatitis or contact dermatitis.
Related topics: Orbital Cellulitis, Preseptal Cellulitis
L03.90 – Cellulitis, unspecified
128045006 – Cellulitis
The differential for cellulitis is vast, and time course, drug / exposure history, and the presence / absence of systemic features should help delineate the cause. The differential diagnosis for suspected cellulitis of the head / scalp includes:
- Tinea capitis (favus, kerion)
- Herpes zoster
- Acne keloidalis nuchae
- Dissecting cellulitis of the scalp
- Folliculitis decalvans
- Central centrifugal cicatricial alopecia
- Lichen planopilaris
- Inflamed or infected pilar cyst
- Discoid lupus
- Pityriasis amiantacea
- Erosive pustular dermatosis
- Occipital neuralgia