White : Diseases of the Skin - Cellular and Metabolic Cutaneous Infiltrates

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Gary M. White & Neil H. Cox

Diseases of the Skin

11	Cellular and Metabolic Cutaneous Infiltrates

OTHER METABOLIC INFILTRATES AND DEPOSITS

Perforating disorders

This is a group of disorders in which dermal tissue is extruded through the epidermis or into the follicles (perforating folliculitis), a process known as transepidermal elimination (Figs 11.75). This is an important group of disorders, as they are associated with systemic disease, notably diabetes and chronic renal failure, and are discussed further in Chapter 12. However, the same process of transepidermal elimination may occur sporadically and also occurs as isolated lesions in several other situations, which are usually more obvious. For example, subcutaneous suture material (‘spitting’ sutures), fragmented hair shafts (e.g. after simple folliculitis), or insect mouthparts may all be eliminated through the skin surface.

Calcinosis

Cutaneous calcinosis (Figs 11.76) occurs by various mechanisms, the clinical features being very varied and depending on the disease entity.

The major mechanisms are as follows (and are listed, with examples, in Table 11.11).

•	Dystrophic calciﬁcation. In this mechanism, calcium is deposited in previously abnormal tissue or is related to speciﬁc local factors. This occurs, for example, in some connective tissue disorders (widespread in juvenile dermatomyositis, locally in CREST [calcinosis, Raynaud phenomenon, esophageal dysfunction, sclerodactyly, and telangiectasia] syndrome; see Ch.13), occasionally in longstanding venous stasis or Ehlers–Danlos syndrome (Ch.22), and after various injuries. Calciﬁcation of the ear occurs most commonly after cold injury but also in some endocrine disorders. There are also some speciﬁc entities in which calciﬁcation occurs, such as pilomatricoma (a benign tumor of hair follicle origin, Ch. 23).
•	Metastatic calciﬁcation. This occurs due to either elevated calcium or phosphate levels, or both. Most cases occur in renal failure with secondary hyperparathyroidism. Rarely, this may cause deposits of calcium in the skin; the more signiﬁcant disorder that occurs is calciﬁc uremic arteriolopathy, which is discussed in Chapter 12.
•	Idiopathic calciﬁcation. At least some examples of apparent idiopathic calciﬁcation are probably due to unrecognized injury and are really dystrophic in type.

Fig. 11.75 Perforating folliculitis in a renal transplant recipient. These lesions are often quite pruritic, and relatively difﬁcult to treat. In this instance, they responded to prompt application of a potent topical corticosteroid ointment.

Fig. 11.76 Calcinosis cutis: (a) showing small striate plaques that are ﬁrm to touch, (b) showing an ulcerated lesion with typical white color of the calciﬁed plaque

Table 11.11 SOME EXAMPLES OF CUTANEOUS CALCINOSIS
Mechanism of calcinosis	Examples
Dystrophic	Post-traumatic: scars, hematomas, fat injury Localized lesions: cysts, angiomas, lipomas Neoplastic: pilomatricoma, some sarcomas Inflammatory diseases: sclerodermas, dermatomyositis, acne Other skin conditions: venous stasis disease, pseudoxanthoma elasticum, Ehlers–Danlos syndrome
Metastatic	Hyperparathyroidism, pseudohypoparathyroidism, chronic renal failure, milk-alkali syndrome Sarcoidosis Malignant disease with hypercalcemia
Idiopathic	Calcinosis universalis, calcinosis circumscripta Solitary nodular calcinosis (cutaneous calculus) Idiopathic calcinosis of the scrotum

Gout

Etiology and pathogenesis

Gout is a disorder in which excessive urate is deposited in the tissues. This may occur for a variety of reasons, including a familial tendency, failure of excretion (e.g. chronic renal failure), or excessive purine load (e.g. from breakdown of damaged cells during chemotherapy).

Clinical features

Gout primarily affects the joints, causing severe acute pain. However, in chronic gout there may be development of cutaneous nodules known as tophi (Figs 11.77)and Figs 11.78) These affect primarily the ﬁngers and the ears. They are hard, yellowish white subcutaneous nodules.

Fig. 11.77 Gouty tophi on the ﬁnger. The lesions are hard, and white or yellowish. Large lesions may need to be treated surgically (Figs 2.29a), but smaller lesions may resolve when prophylactic treatment is established, as in this case

Fig. 11.78 Gouty tophi on the ear. The antihelix is the typical site. Multiple yellowish nodules at this site on the ear in a patient without joint disease are unlikely to be due to gout, and granuloma annulare should be considered (Figs 11.23).

Fig. 11.79 Waxy yellowish deposits in the skin in chronic erythropoietic protoporphyria. This disorder is apparent as severe and immediate photosensitivity in early childhood, but it may be relatively asymptomatic in later years. The liver may also be affected in some cases. (Courtesy of Gary W. Cole, M.D.)

Differential diagnosis

On the ﬁngers, the differential diagnosis includes bony abnormalities, such as Heberden nodes; other abnormal tissue deposits, such as calcinosis; and some ﬁrm cutaneous nodules, such as foreign body reactions. On the ears, the most common mimic of gouty tophi is GA, which may also present as multiple nodules over the antihelix (seeFigs 11.23. Solitary nodules on the ear may be confused with chondrodermatitis nodularis (Ch. 30) or pilomatricoma (Ch. 23).

Treatment

Individual tophi may be excised if required. Prophylactic treatment of the underlying metabolic disorder should be instituted with allopurinol.

Porphyrias

Porphyrias are discussed in Chapter 17. However, the yellowish waxy scars that may occur in erythropoietic protoporphyria( Figs 11.79) may be confused with other tissue inﬁltrates such as xanthomas or mucinoses, especially in older patients in whom the photosensitive symptoms may have abated considerably compared with childhood years. The main differential diagnosis of these lesions if they occur in younger patients is a rare inherited condition known as lipoid proteinosis.

Lipoid proteinosis

Also termed hyalinosis cutis et mucosae or Urbach–Wiethe disease, this is an autosomal recessive disorder in which hyaline material is deposited in various organs. In the skin, waxy papules develop mainly around eyelid margins, nose, and lips. The skin is generally thickened and may appear verrucous over extremities or bony prominences. Hoarseness due to laryngeal involvement is an early feature that may suggest the diagnosis. Dental abnormalities and sickle-shaped calciﬁcation of the temporal lobes occur.

The main differential diagnoses are other deposition disorders such as porpyhria (discussed earlier), amyloidosis, mucinoses, or histiocytoses.