DISORDERS OF DERMIS DISORDERS OF SUBCUTANEOUS FA

While developmental dermal disorders, e.g. Ehler- Danlos syndrome, Cutis laxa, etc. have been discussed in Ch 25.2, important acquired disorders of dermis are as follows:

Keloids (hypertrophic scars) are sharply demarcated benign nodular lesions, formed over healing site, due to overgrowth of collagen tissue.

Clinically these lesions present as tender, reddish, deep seated nodules of variable size (1-10 cm), mostly over shin of tibia bilaterally. Nodules gradually turn bluish over 1-2 weeks and disappear by 3-4 weeks leaving a brownish hyperpigmentation.

No treatment is necessary except NSAIDs for relief of pain, though effort should be made to identify etiology. Striae cutis distensae are thin, depressed, silvery and smooth bands of atrophic skin, usually seen lower abdomen and thighs. These lesions are caused by over distension and stretching of skin during periods of rapid growth, e.g. adolescence or during pregnancy, obesity, ascites, Cushing syndrome, etc. and may become less conspicuous with time.

Scleredema adultorum, may begin in late childhood, with sudden onset of brawny, non-pitting edema of the face and neck that rapidly spreads to thorax and arms. Abdomen and legs are usually spared. The face acquires a waxy, mask-like appearance but with normal skin color. Active phase lasts for 4-8 weeks followed by gradual spontaneous resolution, though recurrence is common. Over 70% of these cases are preceded by streptococcal or viral infections. Skin biopsy reveals increased dermal thickness due to swelling of collagen bundles and increased mucopolysaccharide content.

TABLE 25.11: Causes of erythema nodosum

• Infections:

- Bacterial: Streptococci, leptospirosis, diphtheria

- Mycobacteria: TB, leprosy

- Viral: HSV, EBV, enteroviruses

- Parasitic: Toxoplasmosis, filariasis, helminths

- Others: Syphilis, systemic fungal infections

• Drugs:

- Antibiotics: Sulphonamides

- Anticonvulsants: Phenytoin

- Others: Aspirin, oral contraceptives

• Systemic disorders:

- Autoimmune: JIA, Crohn's disease, sarcoidosis

- Malignancies: Leukemia

EBV: Epstein-Barr virus; JIA: Juvenile idiopathic arthritis Some important disorders of subcutaneous fat are as follows:

Panniculitis is the inflammation of subcutaneous fat due to non-infective causes, presenting as local nodules (poststeroid therapy, post-injection site, SLE, #945;-1- antitrypsin deficiency, etc.) or large, hard plaques (cold exposure, sclerema neonatorum and subcutaneous fat necrosis, etc.)

Subcutaneous fat necrosis, due to saponification of subcutaneous fat, is usually seen in asphyxiated newborns. Clinically, it presents as rubbery, erythematous or violaceous plaques/nodules over fatty areas, e.g. cheeks, buttocks, thighs, etc. It involutes spontaneously after many weeks/months without scarring. Hypercalcemia may be associated in these cases.

Sclerema neonatorum is a bad prognostic indicator, typically seen in critically sick newborns, specially with sepsis or hypothermia. Clinically, it is characterised by diffuse, woody induration of the skin, most prominent over face and bony points. In severe cases, face assume mask-like appearance with restriction of joint mobility. Outcome depends on primary illness.

Unlike subcutaneous fat necrosis, histopathology in sclerema neonatorum is characterized by hypertrophy of fat cells with increased intracellular spaces, without any evidence of inflammation.

Lipodystrophy may be generalized or partial and congenital or acquired.

Congenital generalized lipodystrophy is an autosomal recessive disorder, characterized by progressive loss of subcutaneous and visceral fat since early infancy with other skin manifestations, e.g.

Acquired generalized lipodystrophy with similar presentation is known in older children following viral infections or unexplained illnesses, perhaps due to autoimmune destruction of adipose cells.

Partial lipodystrophy is more common and may be idiopathic or secondary, e.g. insulin lipoatrophy.

Idiopathic partial lipoatrophy is more common in females, presenting in late childhood with gradual symmetrical loss of subcutaneous tissue, predominantly from face and trunk (Cadaver face). Exact cause is unknown, though some cases have chronic renal disease or abnormal lipid profile.

Insulin lipoatrophy develops after 1-2 year of insulin therapy, presenting as well-circumscribed dimple at the site of injections. Cross reactivity of insulin antibodies with adipose cells is implicated in etiology, though lesions may be prevented by rotation of injection sites.

25.10