Acne agminata

(Ref. Pathology of the skin, PH McKee, 3rd Ed. Elsevier-Mosby)

Clinical features

Acne agminata (lupus miliaris disseminatus faciei, acnitis, papular tuberculid) is a rare condition first thought to be a form of tuberculid but an association with tuberculosis has since been excluded. Some authors consider this disease to be synonymous with granulomatous rosacea. However, the distinctive clinical presentation, and the absence of typical rosacea in patients affected by the disease, argue against this possibility. Recently, a new name has been suggested for the disease: facial idiopathic granulomata with regressive evolution (F.I.G.U.R.E).'

Clinical presentation is characterized by fairly monomorphous, yellowish-brown papules typically involving the central face with predilection for periocular areas. Involvement of axillae or upper limbs is exceptionally present. There is no sex predilection and the age range is wide although most cases occur in young, to middle-aged adults. An exceptional case has been documented during pregnancy. Response to conventional treatment for rosacea is often ineffective but lesions tend to regress spontaneously over a period of months or even years leaving mild scarring.

 

Pathogenesis and histological features

As suggested by some synonyms, infection by mycobacteria has been favored by some authors as a potential cause. This theory is no longer tenable due to the absence of past or present systemic tuberculosis and the constant failure of isolation of bacilli. In one study from Israel mycobacterial DNA was not detected by PCR. It bas been suggested that development of the lesions is due to an unusual granulomatous, reaction to ruptured hair follicles.

The histological features vary with the stage of evolution and may be entirely non-specific. A biopsy from a well-established lesion shows a central area of well-defined caseous necrosis surrounded by multinucleated giant cells and epithelioid cells (sometimes indistinguishable from tuberculous infection). Serial sections often reveal relationship of the necrosis to a destroyed hair follicle. Special stains may demonstrate a ring of elastic fibers in the center of the necrotic focus, possibly representing the isthmus of the hair follicle. The granulomata are not usually related to Demodex folliculorum as is often the case in granulomatous rosacea. Focal vasculitis is only exceptionally seen.

 

Differential diagnosis

The diagnosis is fairly easy in the presence of granulomata surrounding an area of caseation necrosis since the latter is not usually a feature of either granulomatous rosacea or perioral dermatitis. In biopsies showing only focal granulomatous inflammation, establishing the diagnosis may require very close clinicopathological correlation.