A middle-aged patient with a pustular dermatosis with inguinal lymphadenopathy

A 43-year old man, resident of Akola, without any known comorbidity, had a history of fever, and presented elsewhere with joint pains and bullous lesions in both inguinal regions with weight loss of 4kgs over three months. A right inguinal lymph node biopsy had shown dilated sinuses filled with lymphocytes, plasma cells and histiocytes. The histiocytes showed round vesicular nuclei and abundant foamy cytoplasm, reported as diagnostic of Rosai Dorfman disease (RD). The patient had received multiple antibiotics, symptomatic treatment but no steroids. However, new lesions appeared over his back, hands, thighs and legs over the next few weeks.

This prompted referral three months later. He had a nutritional anaemia (Hb: 72 g/l), leucocytosis (18.4 × 10⁹ /L), raised ESR (72 mm/1^st h) and his HIV serology was negative. On physical examination there were vesiculo-pustular lesions involving the extensor surfaces. A few of these were surrounded by erythema and there were pigmented lesions involving the palms (Figure. 1). He had loss of eyebrows laterally and a tender nodular lesion over his nose. There was no evidence of numbness or motor weakness.

OPEN IN VIEWER

Figure 1.

Vesiculo pustular lesion.

Our differential diagnosis included pemphigus, bullous pemphigoid, epidermolysis bullosa acquisita, IgA related dermatoses, and pustular psoriasis. ¹ The size and pattern of distribution of the vesiculo-pustular lesions, the presence of systemic and localised signs of inflammation, the absence of any itching over the lesions were not however consistent. Although fever may be present in pustular psoriasis, the vesiculo-pustular lesions do not appear in crops; moreover, there was no background of psoriasis. Infectious conditions including staphylococcal pustulosis, streptococcal infection, primary herpes simplex (HSV), varicella zoster (HVZ), were therefore also considered. The prolonged course, lack of fever and lack of response to multiple antibiotic courses and negative bacterial culture ruled out these. ² The generalised extensor surface distribution of the lesions made the diagnosis of HSV unlikely, which is more common in the mucocutaneous junctions. A dermatomal distribution of the lesions was not seen, which made HZV unlikely. Among non-infectious conditions, RD is a rare pseudo-lymphomatous disorder of unknown aetiology which commonly affects middle aged men, but rarely affects people of Asian origin. ³ Cutaneous RD occurs more often in females in their 20s or 30s.

This left Mycobacterial infection most likely. Biopsy of the pustular lesion was done in preference to a slit skin smear, with the notion that the yield will be better. Skin biopsy was positive for Mycobacterium leprae (modified Ziehl Nielsen stain, using 5% H₂SO₄). Numerous solid as well as fragmented acid-fast bacilli was seen arranged discretely as well as in clusters ⁴ (Figure 2). The skin biopsy sample was negative for M. TB in ZN staining as well as in genexpert ultra.

OPEN IN VIEWER

Figure 2.

Modified acid fast stain (5% H2So4): positive for AFB.

Histopathology confirmed nodular granulomatous inflammation centred around neurovascular bundles involving the superficial and deep dermis consisting of foamy macrophages ⁵ and lymphocytes with loss of epidermal rete pattern. These findings were consistent with ENL.

Re-examination of the patient indeed revealed thickened bilateral common peroneal nerves. Electrophysiological tests were not done as they do not have contributed to the diagnosis. The patient was treated with standard multidrug regimen (MDR) (rifampicin, clofazimine and dapsone) and oral prednisolone (1 mg/kg). At one-month follow-up, he had improved clinically and therefore prednisolone was tapered gradually. In this case no obvious human source of infection was apparent and the screening of family members was advised.

This case demonstrates that, unusual forms of ENL ⁶ continue to be a diagnostic challenge for clinicians. The common manifestations of ENL include the development of new painful, tender and erythematous subcutaneous nodules, associated with polymorphonuclear leucocytosis. The vesiculopustular form occurs in more immunosuppressed patients with vasculitis, pustule formation and ulceration, on the background of borderline lepromatous or lepromatous leprosy. ⁶ The presence of foamy macrophages on histopathology should alert the need to perform stains for M. leprae. A detailed clinical history and examination, clinician's knowledge about the cardinal signs & uncommon presentation of leprosy, biopsy from proper site and careful review of histopathology can help in proper diagnosis and management. Reporting a rare disease like RD and accepting the diagnosis as a fait accompli can set the clinician on the wrong track. Our case underscores the principle that an uncommon manifestation (vesiculopustular form) of a common disease (such as leprosy) is more likely than a common presentation of a rare disease (such as RD).